Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates

Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates Monica Lima, Rebeca Mousquer, Henrique Costa This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6503555/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective To measure the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns to define anatomical reference values for neonatal biometric device design. Study Design A cross-sectional study conducted at a public university hospital in southern Brazil. Anthropometric measurements were obtained bilaterally from 34 full-term newborns (39–41 weeks gestation) using a precision digital caliper. Result The mean length of the 2nd to 5th digits was 9.23 ± 0.58 mm, with no significant differences by side or sex. The 1st digit was consistently longer (p < 0.01), and the 2nd digit was slightly longer in males (p = 0.04). Palmar, hallucal, and heel measurements showed no significant variation. Conclusion The thumb is the most favorable site for fingerprint capture. The findings provide foundational data for the development of safe and effective neonatal biometric technologies and support equitable identification from birth, aligning with SDG 16.9 of the United Nations. Scientific community and society/Developing world Scientific community and society/Scientific community newborn anthropometry fingerprints personal identification biometry Figures Figure 1 Figure 2 What is already known on this topic Biometric identification in newborns is challenged by anatomical constraints such as small finger size and undeveloped dermatoglyphic patterns. Most biometric systems are designed for adults or older infants, lacking reference parameters specific to the neonatal population. What this study adds Provides original anthropometric measurements of the 1st to 5th digits, palmar, hallucal, and heel regions in full-term newborns. Establishes reference dimensions essential for designing neonatal-specific biometric sensors, contributing to safer in-hospital identification and facilitating early civil registration. Demonstrates that standardization of capture parameters is feasible regardless of sex or laterality in full-term newborns. Introduction In a paradox of precision and challenge, biometrics has become the backbone of individual identification in the digital age. With advanced systems such as facial recognition, iris scanning, and fingerprinting, biometric authentication for adults is now one of the most reliable and secure methods worldwide. However, while it operates with extremely high levels of accuracy and efficiency, its application in newborns still faces considerable challenges — creating a technological paradox: we have mastered digital identification in adults, yet we are still unable to ensure a universally reliable method for newborn identification remains elusive 1 – 4 The integration of biometric fingerprinting in perinatal care may reduce mismatches in newborn identification, thereby enhancing safety protocols in Neonatal Intensive Care Units (NICUs) and improving linkage to essential neonatal services. Ensuring biometric identification from birth also aligns with Sustainable Development Goal 16.9, which aims to provide legal identity for all, including birth registration, by 2030 5 . Challenges span a wide spectrum of complexity, but five key questions are crucial to guide the level of scientific and financial investment required for the development of effective neonatal biometric identification equipment: a) What is the size of newborns’ fingers, and therefore, what should be the dimensions of the capture area to be developed?; b) Where are the fingerprints located in the first days of life?; c) What is the size of neonatal fingerprints, and consequently, what resolution is required to obtain images that ensure reliable biometric processing?; d) How can images be collected from newborns without violating minimum handling protocols and while meeting all safety and comfort requirements? and, e) How can fingerprints be obtained if the dermal ridges have not yet emerged on the epidermis? 6 , 7 To begin with, specific measurement of newborns’ hands is not a routine practice in standard anthropometric assessment protocols. It is generally reserved for specific situations, such as the presence of genetic syndromes or malformations affecting the development of extremities 8 – 11 . There are, however, reference data available for finger length during the second trimester of gestation, with specific percentiles (5th, 50th, and 95th) reported for finger lengths between 14 and 27 weeks of gestation. These values are useful for evaluating fetal development and identifying potential genetic anomalies that may manifest as deviations in finger length 12 . In newborns, finger measurements can vary significantly based on factors such as sex, genetics, and health conditions. Although some studies have investigated sex-related differences in digit proportions among infants, the literature remains limited in providing specific percentile references for the neonatal population 13 – 15 . This information, seemingly simple yet largely unknown, forms a fundamental basis for the development of neonatal biometric identification devices, as it addresses one of the earliest design decisions: what should be the size of the capture area to be developed? Despite advances in infant and child biometrics, little is known about the precise anatomical parameters of the newborn hand and foot required for sensor design. Thus, this study aims to define anatomical reference values for the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns, providing foundational parameters for the development of neonatal identification tools. Methods This cross-sectional study was conducted between January and March 2023 in the NICU of a public university hospital in southern Brazil. Anthropometric measurements were obtained from 34 full-term newborns using a Mitutoyo 150 mm digital caliper adapted with protective edges to prevent injury. The newborns included had gestational ages of 39, 40, or 41 weeks, were appropriate for gestational age 16 , 17 , had intact membranes up to 48 hours prior to delivery, and were less than 48 hours postnatal age at the time of data collection. All measurements were performed by a trained neonatologist with over a decade of clinical experience, enhancing consistency and minimizing measurement bias (Fig. 1 ). Data Analysis Measures of central tendency and dispersion are expressed as means and standard deviations (mean ± SD), while categorical variables are presented as absolute and relative frequencies. Considering a significance level of 5%, a beta of 10%, a standard deviation of 2.5 mm, and a minimum expected difference of 0.6 mm, the estimated minimum sample size was 340 digits. Although only 34 full-term newborns were included in the study, the analysis was based on individual measurements of the 1st to 5th digits, totaling 340 anatomical units. This approach is appropriate given that the study does not aim to make general population inferences, but rather to define specific biometric parameters essential for the design of neonatal fingerprint sensors. Since sensor performance depends on precise digital dimensions, using the digits as the unit of analysis ensures sufficient statistical power while directly supporting the development of accurate and tailored biometric technologies for newborns. The study was approved by the Human Research Ethics Committee, affiliated with the Brazilian National Research Ethics Commission (CONEP/Brazil), under protocol number 53017321.0.0000.0096, and was conducted in accordance with the Declaration of Helsinki and follows the guidelines for the presentation of cross-sectional studies outlined in the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement (EQUATOR Reporting Guidelines) 18 . Results Anthropometric measurements of the 1st to 5th digits, palmar, hallucal, and heel regions were obtained from 34 newborns, of whom 19 (55.9%) were male and 15 (44.1%) were female. The mean gestational age was 39.5 ± 0.7 weeks, with a mean birth weight of 3,371.8 ± 444.3 grams. All newborns were appropriate for gestational age and had a postnatal age at the time of data collection of 30.1 ± 10.3 hours (IQR = 23.2–38.7). Eighteen newborns (52.9%) had a gestational age of 39 weeks, while 16 (47.1%) were 40 or 41 weeks. The Apgar score at the 1st minute was ≥ 7 in 31 cases (91.2%), and all newborns had an Apgar score ≥ 7 at the 5th minute (100%). Maternal comorbidities were recorded in 24 cases (70.5%), with the most frequent being hypertension and/or hypertensive disorders of pregnancy (n = 6), and Group B Streptococcus infection (n = 5). The mean measurement of the 2nd to the 5th digits was 9.23 ± 0.58 mm, with no significant differences between the right and left hands of either girls or boys (p > 0.05). The distal phalanx of the 1st digit (thumb) was significantly larger than those of the other digits in both sexes and on both hands (p < 0.01). Additionally, the distal phalanx of the 2nd digit was approximately 0.60 mm longer in boys compared to girls, both on the right (p = 0.04) and left hand (p = 0.03) (Table 1 ). Table 1 Distal phalanx measurements of the 1st to 5th digits according to sex and laterality Digit Side Female (mean ± SD, mm) Male (mean ± SD, mm) p1-value (female side comparison) p2-value (male side comparison) p3-value (sex comparison for right-side) p4-value (sex comparison for left-side) 1st (thumb) Right 10.92 ± 1.20 10.68 ± 1.19 p = 0.24 p = 0.77 p = 0.99 Left 10.44 ± 1.06 10.80 ± 1.20 p = 0.53 2nd Right 8.76 ± 0.86 9.39 ± 0.92 p = 0.73 p = 0.81 p = 0.04 Left 8.85 ± 0.64 9.46 ± 0.96 p = 0.03 3rd Right 9.84 ± 1.17 10.00 ± 0.80 p = 0.91 p = 0.82 p = 0.65 Left 9.88 ± 1.02 9.97 ± 1.02 p = 0.80 4th Right 9.34 ± 0.98 9.70 ± 0.76 p = 0.30 p = 0.47 p = 0.52 Left 8.98 ± 1.02 9.50 ± 0.87 p = 0.12 5th Right 8.18 ± 0.81 8.62 ± 0.81 p = 0.20 p = 0.22 p = 0.12 Left 8.57 ± 0.94 8.34 ± 0.79 p = 0.38 Statistical tests: comparisons between sides (Paired Student’s t-test) and sexes (Student’s t-test). Values expressed as mean ± standard deviation (SD). No statistically significant differences were observed between sexes or sides (p > 0.05) As illustrated in Fig. 2 , the distal phalanx of the 1st digit (thumb) consistently showed the greatest length compared to the other digits in both sexes and on both hands (p < 0.01). The 2nd digit in males was approximately 0.6 mm longer than in females, on both right (p = 0.04) and left (p = 0.03) sides. No significant differences were observed between the right and left hands within each sex (p > 0.05). These patterns reinforce the anatomical consistency across hands and highlight the thumb’s suitability as the primary site for biometric capture. As presented in Table 2 , no statistically significant differences were observed in the measurements of the palmar, hallucal, and heel regions between male and female newborns, nor between the right and left sides (p > 0.05). The mean values across all regions demonstrated a high degree of anatomical symmetry and consistency between sexes. These results suggest that biometric devices designed for these regions do not require sex-related or side-specific calibration, further supporting the feasibility of standardizing capture dimensions for neonatal applications. Table 2 Mean measurements and 95% confidence intervals for the palmar, hallucal, and heel regions, between sexes or sides (right and left sides) Area Side Female (mean ± SD, mm) Male (mean ± SD, mm) p1-value (female side comparison) p2-value (male side comparison) p3-value (sex comparison for right-side) p4-value (sex comparison for left-side) Palmar height Right 33.86 ± 2.61 34.71 ± 1.46 0.90 0.80 0.23 Left 33.76 ± 2.43 34.83 ± 1.37 0.11 Palmar width Right 30.76 ± 2.89 31.92 ± 2.10 0.64 0.96 0.18 Left 31.19 ± 2.35 31.95 ± 2.13 0.33 Hallucal height Right 23.04 ± 3.62 23.37 ± 2.62 0.66 0.58 0.75 Left 23.54 ± 2.93 23.75 ± 0.45 0.82 Hallucal width Right 10.59 ± 1.51 10.59 ± 1.80 0.73 0.81 0.99 Left 10.39 ± 1.87 10.72 ± 1.33 0.55 Heel height Right 13.62 ± 1.82 14.15 ± 1.92 0.39 0.91 0.42 Left 14.11 ± 1.39 14.22 ± 1.70 0.84 Statistical tests: comparisons between sides (Paired Student’s t-test) and sexes (Student’s t-test). Values expressed as mean ± standard deviation (SD). No statistically significant differences were observed between sexes or sides (p > 0.05) Discussion The mean measurement of the 2nd to 5th digits in full-term and late-term newborns was 9.23 ± 0.58 mm, with no significant differences between the right and left hands in either girls or boys. The distal phalanx of the 1st digit (thumb) was consistently larger than that of the other digits in both sexes and on both sides. Measurements of the palmar, hallucal, and heel regions were similar between male and female newborns, with no significant differences between right and left sides. Although the primary purpose of this study was to provide technical parameters for the development of neonatal fingerprint capture devices, the anthropometric findings also carry important clinical implications. The observed symmetry in distal phalanx measurements between the right and left hands in both sexes suggests that biometric devices do not need to differentiate between hands, simplifying sensor design and positioning protocols in clinical settings. Furthermore, the consistent observation that the 1st digit (thumb) is significantly larger than the others in both males and females reinforces its potential as the preferred site for biometric acquisition in newborns. The slightly greater length of the 2nd digit in male newborns, although modest, may indicate subtle sex-related anatomical variation already present at birth—an aspect relevant for the calibration of high-precision biometric systems. While these differences may not yet translate into clinical decision-making, they establish foundational evidence for the development of technologies that ensure both the feasibility and accuracy of biometric identification in perinatal care. The development of the fingers during the fetal stage is a complex process involving the formation and growth of bones, cartilage, and soft tissues. The formation of digits and joints during limb development is an integrated process that occurs simultaneously at the distal end of the digital rays 19 . This process is regulated by signaling mechanisms, including transforming growth factor beta (TGFβ), which plays a crucial role in digit morphogenesis, including the formation of the fingers, digital tendons, and interphalangeal joints 20 . During the fetal period, histological and morphometric analysis of the metacarpal and carpal bones reveals that longitudinal growth of long bones occurs in the transition zone between the epiphysis and diaphysis, similar to the metaphyseal growth plate observed in later stages of development 21 . In addition, the transverse growth of the metacarpal bones is an eccentric process, in which the bones grow away from the midline of the hand through eccentric apposition of bone, rather than through the expansion of soft tissues 22 . The ratio between the length of the metacarpal bones and the fingers is established in utero, with gestational age-specific growth curves that can be used to detect anomalies such as brachydactyly, for example 23 . The development of fingerprints, which are complex epithelial structures, occurs through a Turing reaction-diffusion system involving signaling pathways such as EDAR (Ectodysplasin A Receptor), WNT (Wnt/β-catenin), and antagonistic BMP (Bone Morphogenetic Protein) pathways. These processes are regulated by a combination of genetic and environmental factors that interact to ensure the proper development of the fingers during gestation 24 . Some authors suggest that finger development exhibits sex-related differences, particularly regarding finger length and the ratio between digits. The literature indicates that the ratio between the second and fourth digits (2D:4D) serves as a marker of exposure to sex hormones during fetal development. In general, males tend to have a lower 2D:4D ratio than females, which is attributed to higher prenatal exposure to androgens 13 , 25 , 26 . Such anatomical and developmental variations are particularly relevant when designing biometric systems aimed at newborns. Fingerprint biometric devices are engineered to capture, process, and verify individuals' fingerprints and are widely used in security systems, access control, and identity authentication. These devices range from simple scanners to advanced integrated systems and typically use optical sensors based on light reflection to create an image of the fingerprint ridges and valleys. In current applications, the capture area of these devices usually ranges from 12.5 mm × 16.25 mm to 20 mm × 25 mm 27 . Capacitive sensors, commonly used in mobile devices and biometric cards, have capture areas ranging from 8 mm × 8 mm to 15 mm × 20 mm. Ultrasonic sensors, used in smartphones, typically range from 8 mm × 8 mm to 20 mm × 30 mm. Multi-finger scanners, employed for identification purposes, have larger capture areas, ranging from 40 mm × 40 mm to 80 mm × 80 mm 28 . Newborns clearly require a smaller and highly sensitive capture area to recognize the subtle details of dermatoglyphs, especially considering that the ridge and valley widths are significantly smaller than those of an adult. Efficient capture in this case demands equipment with high resolution and a capture area appropriately scaled to the size of the newborn's finger 27 – 28 . A capture area larger than the size of the phalanx may hinder the proper positioning of very small fingers, and an overly large sensor may capture more than just the finger, including adjacent areas of the hand or even blurred regions and elements that could be mistaken for fingerprint patterns. If the newborn's finger is not properly positioned at the center of the capture area, the resulting image may be partial, blurred, or contain artifacts, thereby reducing fingerprint accuracy. When the capture area is too large and the resolution is fixed, the same details are distributed across more pixels, potentially lowering image sharpness. On the other hand, if the resolution is sufficiently high, a large capture area can still preserve sharp details. Larger sensors may also require adjustments in touch pressure, as newborns do not apply uniform pressure when placing their fingers on the sensor. This can lead to issues such as smudged areas, incomplete fingerprints, or failed readings. Additionally, larger capture areas may increase acquisition time, raising the likelihood of motion blur due to spontaneous infant movements. Therefore, designing a capture area specifically tailored to newborns is the first step toward developing an efficient and safe neonatal biometric device 6 , 7 , 30 . Several benefits of neonatal biometric solutions are evident and lie in hospital security, prevention of human trafficking, and border protection, as well as birth registration in remote areas and the potential to revolutionize the efficiency of food security, vaccination, and public health programs. Each of these applications deserves attention in addressing this technological paradox that still leaves newborns and children vulnerable in one of their most fundamental rights 6 , 7 . Establishing reliable biometric standards for newborns is not only a technological necessity but a public health imperative to ensure that every child has a secure identity from birth. This study provides novel anthropometric data on the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns, offering critical parameters for the development of neonatal biometric identification systems. The anatomical consistency observed between sexes and sides suggests that sensor designs do not need to be sex- or side-specific, which simplifies standardization and enhances clinical applicability. Notably, the thumb (1st digit) emerged as the most favorable site for fingerprint acquisition due to its relatively greater surface area. This study represents one of the first efforts to provide practical, anatomically grounded parameters specifically designed for the development of identification tools for newborns. Unlike previous approaches that focused primarily on algorithm performance or feasibility in older infants, this research offers detailed anthropometric data that can directly inform the engineering design of biometric sensors. By identifying the most suitable anatomical regions for fingerprint acquisition in full-term newborns, the findings pave the way for the creation of neonatal-specific technologies capable of improving identification systems, particularly in remote or underserved regions where early civil registration and linkage to public health services remain a challenge. This contribution represents a significant step forward in promoting neonatal safety and advancing equity in healthcare. These results not only provide a technical baseline but also open new perspectives on how biometric identification can be integrated into neonatal care. Clinical Implications The anatomical reference data presented in this study support the development of biometric systems tailored to the unique dimensions of newborns. Such systems can play a pivotal role in ensuring accurate identification in NICUs, reducing the risk of misidentification events. They can be integrated into routine care protocols to prevent newborn switching, enhance maternal-infant matching during hospitalization, and support safe discharge planning. Moreover, their implementation can strengthen early civil registration processes and improve the delivery of public health services such as vaccination programs and nutritional monitoring. Integrating neonatal biometrics into perinatal care protocols may ultimately enhance patient safety, promote equitable access to essential services, and foster a lifelong connection between the child and health systems from birth. While fingerprint acquisition has shown promising results in infants between 4 and 30 days of life—when ridge patterns are more developed and skin tension stabilizes—standardizing capture protocols in the immediate postnatal period remains essential. This is particularly relevant for hospital-based identification systems and early civil registration 30 – 32 . Study Limitations All research involving physical measurements is subject to some degree of variability due to the technique employed. In the context of newborns, this variability may be amplified due to the inherent challenges of handling neonates and the need to minimize discomfort and manipulation. Consequently, it was not possible to perform triplicate measurements, which could have improved precision. However, the use of a single experienced neonatologist, standardized protocols, and a calibrated instrument helped reduce measurement bias, although the absence of inter-observer validation remains a potential limitation. Another limitation relates to the sample size. Although the study included only 34 full-term newborns, the analysis focused on 340 individual digits and other anatomical structures. This approach is appropriate given the anatomical scope of the study and the goal of supporting biometric sensor design. Still, the homogeneous population limits generalizability, and future studies should include more diverse ethnic and geographic groups, as variations in skin thickness, tone, and bone structure may influence sensor calibration and image quality. Furthermore, the study did not include longitudinal follow-up to assess how these anatomical dimensions evolve in the first weeks or months of life—an aspect that may inform the optimal window for biometric enrollment. Finally, although the study establishes technical feasibility, future research should evaluate actual biometric performance, including image quality, feature extraction, and matching accuracy using real-world sensor prototypes. Declarations Ethics Approval The study was approved by the Human Research Ethics Committee of the Hospital de Clínicas Complex, Federal University of Paraná, affiliated with the Brazilian National Research Ethics Commission (CONEP/Brazil), under protocol number 53017321.0.0000.0096, and was conducted in accordance with the Declaration of Helsinki. Conflict of Interest Disclosure All authors declare no conflicts of interest. Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates References Wyci´slik L, Wyci´slik P, Momot A. The Improved Biometric Identification of Keystroke Dynamics Based on Deep Learning Approaches. Sensors. 2024;24:3763. Girdhar N, Sharma D, Kumar R, Sahu M, Lin C-C. Emerging trends in biomedical trait-based human identification: A bibliometric analysis, SLAS Technol. 2024;29(3):100136. Exall A, Harris G, Hussey L, Bandey H, Vassel S. UK National Fingerprint Collaborative Exercise 2022-23. 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Int’l Conference on Image Processing (ICIP), pp.282-285, Thessaloniki, Greece, Oct 7 - 10, 2001. Jain AK, Feng J. Latent Fingerprint Matching. IEEE Trans Pattern Anal Mach Intell. 2011;33(1):88-100. Nel S, de Man J, van den Berg L, Wenhold FAM. Statistical Assessment of Reliability of Anthropometric Measurements in the Multi-Site South African National Dietary Intake Survey 2022. Eur J Clin Nutr. 2024;78(11):1005-1113. Stomfai S, Ahrens W, Bammann K, Kovács E, S, N, et al. Intra-And Inter-Observer Reliability in Anthropometric Measurements in Children. Int J Obes. 2011;35(S1):S45-51. Additional Declarations There is NO conflict of interest to disclose. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6503555","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":449906844,"identity":"40040ed1-6f78-448d-b3c8-a73f97ab9439","order_by":0,"name":"Monica Lima","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCUlEQVRIiWNgGAWjYJCCA0AswwZm2jAw8IPohALCWnggWtIYGCQbQFoMCNvEwwDTYgAygQGPFt323oMHftQw8PCJHX7AzJNwJ9/4/OrEDw8MGOT5xQ5g1WJ25lzCwZ5jQIdJpxkAtTyz3Hbj7WYJoMMMZ85OwK7lRo7BYQY2kJYEA2beH4cNzG6c3QDSkmBwG5+WfyAt6R+Athw2MJ5xdvMPgloY20BacgzAWgz4e7fht+XMGYODvX0SIC0FB+ckPDOQuMG7zSLBQAK3X473GH/48c1GTn52+sYHbxLuGPD3n91880eFjTy/NHYtUCABJg+AkUQCQoQYANTCf4Bo1aNgFIyCUTAyAAC3nl1I1CBBvQAAAABJRU5ErkJggg==","orcid":"","institution":"Federal University of Parana","correspondingAuthor":true,"prefix":"","firstName":"Monica","middleName":"","lastName":"Lima","suffix":""},{"id":449906845,"identity":"dc376a98-f57d-433a-bef4-17d551b9dbda","order_by":1,"name":"Rebeca Mousquer","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Rebeca","middleName":"","lastName":"Mousquer","suffix":""},{"id":449906846,"identity":"858250b7-088c-4e17-84b0-aed0f584007e","order_by":2,"name":"Henrique Costa","email":"","orcid":"","institution":"HA Tecno","correspondingAuthor":false,"prefix":"","firstName":"Henrique","middleName":"","lastName":"Costa","suffix":""}],"badges":[],"createdAt":"2025-04-22 11:06:47","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6503555/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6503555/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82298496,"identity":"31359d6a-67e8-4c84-ba52-a51402f7d995","added_by":"auto","created_at":"2025-05-08 20:23:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":131603,"visible":true,"origin":"","legend":"\u003cp\u003eAnthropometric measurements of the 1st to 5th digit, palmar, hallucal, and heel regions (original illustration by the authors, created in Canva software (www.canva.com).\u003c/p\u003e\n\u003cp\u003eNote: a) Digits: measurement taken from the tip of the digit to the distal flexion crease. b) Palm height and width: height measured from the flexion crease of the 3rd digit to the wrist crease; width measured from the base crease of the thumb to the lateral edge of the palmar surface. c) Hallux height: measurement from the tip of the hallux to the hallux flexion crease. d) Height and width of the hallucal region: height measured from the interdigital area of the hallux to the medial border of the plantar surface; width measured from this imaginary line to the medial edge of the plantar surface.\u003c/p\u003e","description":"","filename":"Figure1JP.png","url":"https://assets-eu.researchsquare.com/files/rs-6503555/v1/fa05df1e855e76bf8b5968ef.png"},{"id":82298494,"identity":"91bbbb1a-3284-453a-a815-dfdfae936995","added_by":"auto","created_at":"2025-05-08 20:23:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":52643,"visible":true,"origin":"","legend":"\u003cp\u003eMeans and 95% confidence intervals for the measurements of the 1st to 5th digits\u003c/p\u003e","description":"","filename":"Figure2JP.png","url":"https://assets-eu.researchsquare.com/files/rs-6503555/v1/069ed7e6416fa70ecfffa6f6.png"},{"id":83498326,"identity":"e131cb1a-fb70-491f-ada7-4318a55baac3","added_by":"auto","created_at":"2025-05-27 12:34:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":835923,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6503555/v1/ec78a1ca-95d8-4e6b-a102-9a46be03bd93.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e conflict of interest to disclose.","formattedTitle":"Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates","fulltext":[{"header":"What is already known on this topic","content":"\u003cul type=\"disc\"\u003e\n \u003cli\u003eBiometric identification in newborns is challenged by anatomical constraints such as small finger size and undeveloped dermatoglyphic patterns.\u003c/li\u003e\n \u003cli\u003eMost biometric systems are designed for adults or older infants, lacking reference parameters specific to the neonatal population.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eWhat this study adds\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eProvides original anthropometric measurements of the 1st to 5th digits, palmar, hallucal, and heel regions in full-term newborns.\u003c/li\u003e\n \u003cli\u003eEstablishes reference dimensions essential for designing neonatal-specific biometric sensors, contributing to safer in-hospital identification and facilitating early civil registration.\u003c/li\u003e\n \u003cli\u003eDemonstrates that standardization of capture parameters is feasible regardless of sex or laterality in full-term newborns.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Introduction","content":"\u003cp\u003eIn a paradox of precision and challenge, biometrics has become the backbone of individual identification in the digital age. With advanced systems such as facial recognition, iris scanning, and fingerprinting, biometric authentication for adults is now one of the most reliable and secure methods worldwide. However, while it operates with extremely high levels of accuracy and efficiency, its application in newborns still faces considerable challenges \u0026mdash; creating a technological paradox: we have mastered digital identification in adults, yet we are still unable to ensure a universally reliable method for newborn identification remains elusive\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe integration of biometric fingerprinting in perinatal care may reduce mismatches in newborn identification, thereby enhancing safety protocols in Neonatal Intensive Care Units (NICUs) and improving linkage to essential neonatal services. Ensuring biometric identification from birth also aligns with Sustainable Development Goal 16.9, which aims to provide legal identity for all, including birth registration, by 2030\u003csup\u003e5\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eChallenges span a wide spectrum of complexity, but five key questions are crucial to guide the level of scientific and financial investment required for the development of effective neonatal biometric identification equipment: a) What is the size of newborns\u0026rsquo; fingers, and therefore, what should be the dimensions of the capture area to be developed?; b) Where are the fingerprints located in the first days of life?; c) What is the size of neonatal fingerprints, and consequently, what resolution is required to obtain images that ensure reliable biometric processing?; d) How can images be collected from newborns without violating minimum handling protocols and while meeting all safety and comfort requirements? and, e) How can fingerprints be obtained if the dermal ridges have not yet emerged on the epidermis?\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eTo begin with, specific measurement of newborns\u0026rsquo; hands is not a routine practice in standard anthropometric assessment protocols. It is generally reserved for specific situations, such as the presence of genetic syndromes or malformations affecting the development of extremities\u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. There are, however, reference data available for finger length during the second trimester of gestation, with specific percentiles (5th, 50th, and 95th) reported for finger lengths between 14 and 27 weeks of gestation. These values are useful for evaluating fetal development and identifying potential genetic anomalies that may manifest as deviations in finger length\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn newborns, finger measurements can vary significantly based on factors such as sex, genetics, and health conditions. Although some studies have investigated sex-related differences in digit proportions among infants, the literature remains limited in providing specific percentile references for the neonatal population\u003csup\u003e\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis information, seemingly simple yet largely unknown, forms a fundamental basis for the development of neonatal biometric identification devices, as it addresses one of the earliest design decisions: what should be the size of the capture area to be developed?\u003c/p\u003e \u003cp\u003eDespite advances in infant and child biometrics, little is known about the precise anatomical parameters of the newborn hand and foot required for sensor design. Thus, this study aims to define anatomical reference values for the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns, providing foundational parameters for the development of neonatal identification tools.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThis cross-sectional study was conducted between January and March 2023 in the NICU of a public university hospital in southern Brazil. Anthropometric measurements were obtained from 34 full-term newborns using a Mitutoyo 150 mm digital caliper adapted with protective edges to prevent injury. The newborns included had gestational ages of 39, 40, or 41 weeks, were appropriate for gestational age\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, had intact membranes up to 48 hours prior to delivery, and were less than 48 hours postnatal age at the time of data collection. All measurements were performed by a trained neonatologist with over a decade of clinical experience, enhancing consistency and minimizing measurement bias (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eData Analysis\u003c/h2\u003e \u003cp\u003eMeasures of central tendency and dispersion are expressed as means and standard deviations (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD), while categorical variables are presented as absolute and relative frequencies.\u003c/p\u003e \u003cp\u003eConsidering a significance level of 5%, a beta of 10%, a standard deviation of 2.5 mm, and a minimum expected difference of 0.6 mm, the estimated minimum sample size was 340 digits. Although only 34 full-term newborns were included in the study, the analysis was based on individual measurements of the 1st to 5th digits, totaling 340 anatomical units. This approach is appropriate given that the study does not aim to make general population inferences, but rather to define specific biometric parameters essential for the design of neonatal fingerprint sensors. Since sensor performance depends on precise digital dimensions, using the digits as the unit of analysis ensures sufficient statistical power while directly supporting the development of accurate and tailored biometric technologies for newborns.\u003c/p\u003e \u003cp\u003eThe study was approved by the Human Research Ethics Committee, affiliated with the Brazilian National Research Ethics Commission (CONEP/Brazil), under protocol number 53017321.0.0000.0096, and was conducted in accordance with the Declaration of Helsinki and follows the guidelines for the presentation of cross-sectional studies outlined in the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement (EQUATOR Reporting Guidelines)\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAnthropometric measurements of the 1st to 5th digits, palmar, hallucal, and heel regions were obtained from 34 newborns, of whom 19 (55.9%) were male and 15 (44.1%) were female. The mean gestational age was 39.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7 weeks, with a mean birth weight of 3,371.8\u0026thinsp;\u0026plusmn;\u0026thinsp;444.3 grams. All newborns were appropriate for gestational age and had a postnatal age at the time of data collection of 30.1\u0026thinsp;\u0026plusmn;\u0026thinsp;10.3 hours (IQR\u0026thinsp;=\u0026thinsp;23.2\u0026ndash;38.7). Eighteen newborns (52.9%) had a gestational age of 39 weeks, while 16 (47.1%) were 40 or 41 weeks. The Apgar score at the 1st minute was \u0026ge;\u0026thinsp;7 in 31 cases (91.2%), and all newborns had an Apgar score\u0026thinsp;\u0026ge;\u0026thinsp;7 at the 5th minute (100%). Maternal comorbidities were recorded in 24 cases (70.5%), with the most frequent being hypertension and/or hypertensive disorders of pregnancy (n\u0026thinsp;=\u0026thinsp;6), and Group B Streptococcus infection (n\u0026thinsp;=\u0026thinsp;5).\u003c/p\u003e \u003cp\u003eThe mean measurement of the 2nd to the 5th digits was 9.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.58 mm, with no significant differences between the right and left hands of either girls or boys (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The distal phalanx of the 1st digit (thumb) was significantly larger than those of the other digits in both sexes and on both hands (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Additionally, the distal phalanx of the 2nd digit was approximately 0.60 mm longer in boys compared to girls, both on the right (p\u0026thinsp;=\u0026thinsp;0.04) and left hand (p\u0026thinsp;=\u0026thinsp;0.03) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDistal phalanx measurements of the 1st to 5th digits according to sex and laterality\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDigit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSide\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep1-value\u003c/p\u003e \u003cp\u003e(female side comparison)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep2-value\u003c/p\u003e \u003cp\u003e(male side comparison)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep3-value\u003c/p\u003e \u003cp\u003e(sex comparison for right-side)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep4-value\u003c/p\u003e \u003cp\u003e(sex comparison for left-side)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1st (thumb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.92\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.68\u0026thinsp;\u0026plusmn;\u0026thinsp;1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.44\u0026thinsp;\u0026plusmn;\u0026thinsp;1.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.80\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2nd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3rd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.84\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.88\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4th\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.98\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5th\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eStatistical tests: comparisons between sides (Paired Student\u0026rsquo;s t-test) and sexes (Student\u0026rsquo;s t-test). Values expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD). No statistically significant differences were observed between sexes or sides (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the distal phalanx of the 1st digit (thumb) consistently showed the greatest length compared to the other digits in both sexes and on both hands (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). The 2nd digit in males was approximately 0.6 mm longer than in females, on both right (p\u0026thinsp;=\u0026thinsp;0.04) and left (p\u0026thinsp;=\u0026thinsp;0.03) sides. No significant differences were observed between the right and left hands within each sex (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). These patterns reinforce the anatomical consistency across hands and highlight the thumb\u0026rsquo;s suitability as the primary site for biometric capture.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, no statistically significant differences were observed in the measurements of the palmar, hallucal, and heel regions between male and female newborns, nor between the right and left sides (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The mean values across all regions demonstrated a high degree of anatomical symmetry and consistency between sexes. These results suggest that biometric devices designed for these regions do not require sex-related or side-specific calibration, further supporting the feasibility of standardizing capture dimensions for neonatal applications.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMean measurements and 95% confidence intervals for the palmar, hallucal, and heel regions, between sexes or sides (right and left sides)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSide\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep1-value\u003c/p\u003e \u003cp\u003e(female side comparison)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep2-value\u003c/p\u003e \u003cp\u003e(male side comparison)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep3-value\u003c/p\u003e \u003cp\u003e(sex comparison for right-side)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep4-value\u003c/p\u003e \u003cp\u003e(sex comparison for left-side)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePalmar height\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.86\u0026thinsp;\u0026plusmn;\u0026thinsp;2.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.71\u0026thinsp;\u0026plusmn;\u0026thinsp;1.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.76\u0026thinsp;\u0026plusmn;\u0026thinsp;2.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.83\u0026thinsp;\u0026plusmn;\u0026thinsp;1.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePalmar width\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.76\u0026thinsp;\u0026plusmn;\u0026thinsp;2.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.92\u0026thinsp;\u0026plusmn;\u0026thinsp;2.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.19\u0026thinsp;\u0026plusmn;\u0026thinsp;2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.95\u0026thinsp;\u0026plusmn;\u0026thinsp;2.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHallucal height\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.04\u0026thinsp;\u0026plusmn;\u0026thinsp;3.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23.37\u0026thinsp;\u0026plusmn;\u0026thinsp;2.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.54\u0026thinsp;\u0026plusmn;\u0026thinsp;2.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHallucal width\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.39\u0026thinsp;\u0026plusmn;\u0026thinsp;1.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeel height\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.62\u0026thinsp;\u0026plusmn;\u0026thinsp;1.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.15\u0026thinsp;\u0026plusmn;\u0026thinsp;1.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eStatistical tests: comparisons between sides (Paired Student\u0026rsquo;s t-test) and sexes (Student\u0026rsquo;s t-test). Values expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD). No statistically significant differences were observed between sexes or sides (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe mean measurement of the 2nd to 5th digits in full-term and late-term newborns was 9.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.58 mm, with no significant differences between the right and left hands in either girls or boys. The distal phalanx of the 1st digit (thumb) was consistently larger than that of the other digits in both sexes and on both sides. Measurements of the palmar, hallucal, and heel regions were similar between male and female newborns, with no significant differences between right and left sides.\u003c/p\u003e \u003cp\u003eAlthough the primary purpose of this study was to provide technical parameters for the development of neonatal fingerprint capture devices, the anthropometric findings also carry important clinical implications. The observed symmetry in distal phalanx measurements between the right and left hands in both sexes suggests that biometric devices do not need to differentiate between hands, simplifying sensor design and positioning protocols in clinical settings. Furthermore, the consistent observation that the 1st digit (thumb) is significantly larger than the others in both males and females reinforces its potential as the preferred site for biometric acquisition in newborns. The slightly greater length of the 2nd digit in male newborns, although modest, may indicate subtle sex-related anatomical variation already present at birth\u0026mdash;an aspect relevant for the calibration of high-precision biometric systems. While these differences may not yet translate into clinical decision-making, they establish foundational evidence for the development of technologies that ensure both the feasibility and accuracy of biometric identification in perinatal care.\u003c/p\u003e \u003cp\u003eThe development of the fingers during the fetal stage is a complex process involving the formation and growth of bones, cartilage, and soft tissues. The formation of digits and joints during limb development is an integrated process that occurs simultaneously at the distal end of the digital rays\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. This process is regulated by signaling mechanisms, including transforming growth factor beta (TGFβ), which plays a crucial role in digit morphogenesis, including the formation of the fingers, digital tendons, and interphalangeal joints\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDuring the fetal period, histological and morphometric analysis of the metacarpal and carpal bones reveals that longitudinal growth of long bones occurs in the transition zone between the epiphysis and diaphysis, similar to the metaphyseal growth plate observed in later stages of development\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. In addition, the transverse growth of the metacarpal bones is an eccentric process, in which the bones grow away from the midline of the hand through eccentric apposition of bone, rather than through the expansion of soft tissues\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe ratio between the length of the metacarpal bones and the fingers is established in utero, with gestational age-specific growth curves that can be used to detect anomalies such as brachydactyly, for example\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The development of fingerprints, which are complex epithelial structures, occurs through a Turing reaction-diffusion system involving signaling pathways such as EDAR (Ectodysplasin A Receptor), WNT (Wnt/β-catenin), and antagonistic BMP (Bone Morphogenetic Protein) pathways. These processes are regulated by a combination of genetic and environmental factors that interact to ensure the proper development of the fingers during gestation\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSome authors suggest that finger development exhibits sex-related differences, particularly regarding finger length and the ratio between digits. The literature indicates that the ratio between the second and fourth digits (2D:4D) serves as a marker of exposure to sex hormones during fetal development. In general, males tend to have a lower 2D:4D ratio than females, which is attributed to higher prenatal exposure to androgens\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSuch anatomical and developmental variations are particularly relevant when designing biometric systems aimed at newborns. Fingerprint biometric devices are engineered to capture, process, and verify individuals' fingerprints and are widely used in security systems, access control, and identity authentication. These devices range from simple scanners to advanced integrated systems and typically use optical sensors based on light reflection to create an image of the fingerprint ridges and valleys. In current applications, the capture area of these devices usually ranges from 12.5 mm \u0026times; 16.25 mm to 20 mm \u0026times; 25 mm\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCapacitive sensors, commonly used in mobile devices and biometric cards, have capture areas ranging from 8 mm \u0026times; 8 mm to 15 mm \u0026times; 20 mm. Ultrasonic sensors, used in smartphones, typically range from 8 mm \u0026times; 8 mm to 20 mm \u0026times; 30 mm. Multi-finger scanners, employed for identification purposes, have larger capture areas, ranging from 40 mm \u0026times; 40 mm to 80 mm \u0026times; 80 mm\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eNewborns clearly require a smaller and highly sensitive capture area to recognize the subtle details of dermatoglyphs, especially considering that the ridge and valley widths are significantly smaller than those of an adult. Efficient capture in this case demands equipment with high resolution and a capture area appropriately scaled to the size of the newborn's finger\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA capture area larger than the size of the phalanx may hinder the proper positioning of very small fingers, and an overly large sensor may capture more than just the finger, including adjacent areas of the hand or even blurred regions and elements that could be mistaken for fingerprint patterns.\u003c/p\u003e \u003cp\u003eIf the newborn's finger is not properly positioned at the center of the capture area, the resulting image may be partial, blurred, or contain artifacts, thereby reducing fingerprint accuracy. When the capture area is too large and the resolution is fixed, the same details are distributed across more pixels, potentially lowering image sharpness. On the other hand, if the resolution is sufficiently high, a large capture area can still preserve sharp details. Larger sensors may also require adjustments in touch pressure, as newborns do not apply uniform pressure when placing their fingers on the sensor. This can lead to issues such as smudged areas, incomplete fingerprints, or failed readings. Additionally, larger capture areas may increase acquisition time, raising the likelihood of motion blur due to spontaneous infant movements. Therefore, designing a capture area specifically tailored to newborns is the first step toward developing an efficient and safe neonatal biometric device\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSeveral benefits of neonatal biometric solutions are evident and lie in hospital security, prevention of human trafficking, and border protection, as well as birth registration in remote areas and the potential to revolutionize the efficiency of food security, vaccination, and public health programs. Each of these applications deserves attention in addressing this technological paradox that still leaves newborns and children vulnerable in one of their most fundamental rights\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eEstablishing reliable biometric standards for newborns is not only a technological necessity but a public health imperative to ensure that every child has a secure identity from birth. This study provides novel anthropometric data on the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns, offering critical parameters for the development of neonatal biometric identification systems. The anatomical consistency observed between sexes and sides suggests that sensor designs do not need to be sex- or side-specific, which simplifies standardization and enhances clinical applicability. Notably, the thumb (1st digit) emerged as the most favorable site for fingerprint acquisition due to its relatively greater surface area.\u003c/p\u003e \u003cp\u003eThis study represents one of the first efforts to provide practical, anatomically grounded parameters specifically designed for the development of identification tools for newborns. Unlike previous approaches that focused primarily on algorithm performance or feasibility in older infants, this research offers detailed anthropometric data that can directly inform the engineering design of biometric sensors. By identifying the most suitable anatomical regions for fingerprint acquisition in full-term newborns, the findings pave the way for the creation of neonatal-specific technologies capable of improving identification systems, particularly in remote or underserved regions where early civil registration and linkage to public health services remain a challenge. This contribution represents a significant step forward in promoting neonatal safety and advancing equity in healthcare.\u003c/p\u003e \u003cp\u003eThese results not only provide a technical baseline but also open new perspectives on how biometric identification can be integrated into neonatal care.\u003c/p\u003e"},{"header":"Clinical Implications","content":"\u003cp\u003eThe anatomical reference data presented in this study support the development of biometric systems tailored to the unique dimensions of newborns. Such systems can play a pivotal role in ensuring accurate identification in NICUs, reducing the risk of misidentification events. They can be integrated into routine care protocols to prevent newborn switching, enhance maternal-infant matching during hospitalization, and support safe discharge planning. Moreover, their implementation can strengthen early civil registration processes and improve the delivery of public health services such as vaccination programs and nutritional monitoring. Integrating neonatal biometrics into perinatal care protocols may ultimately enhance patient safety, promote equitable access to essential services, and foster a lifelong connection between the child and health systems from birth.\u003c/p\u003e \u003cp\u003eWhile fingerprint acquisition has shown promising results in infants between 4 and 30 days of life\u0026mdash;when ridge patterns are more developed and skin tension stabilizes\u0026mdash;standardizing capture protocols in the immediate postnatal period remains essential. This is particularly relevant for hospital-based identification systems and early civil registration\u003csup\u003e\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Study Limitations","content":"\u003cp\u003eAll research involving physical measurements is subject to some degree of variability due to the technique employed. In the context of newborns, this variability may be amplified due to the inherent challenges of handling neonates and the need to minimize discomfort and manipulation. Consequently, it was not possible to perform triplicate measurements, which could have improved precision. However, the use of a single experienced neonatologist, standardized protocols, and a calibrated instrument helped reduce measurement bias, although the absence of inter-observer validation remains a potential limitation.\u003c/p\u003e \u003cp\u003eAnother limitation relates to the sample size. Although the study included only 34 full-term newborns, the analysis focused on 340 individual digits and other anatomical structures. This approach is appropriate given the anatomical scope of the study and the goal of supporting biometric sensor design. Still, the homogeneous population limits generalizability, and future studies should include more diverse ethnic and geographic groups, as variations in skin thickness, tone, and bone structure may influence sensor calibration and image quality.\u003c/p\u003e \u003cp\u003eFurthermore, the study did not include longitudinal follow-up to assess how these anatomical dimensions evolve in the first weeks or months of life\u0026mdash;an aspect that may inform the optimal window for biometric enrollment. Finally, although the study establishes technical feasibility, future research should evaluate actual biometric performance, including image quality, feature extraction, and matching accuracy using real-world sensor prototypes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003eEthics Approval\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the Human Research Ethics Committee of the Hospital de Cl\u0026iacute;nicas Complex, Federal University of Paran\u0026aacute;, affiliated with the Brazilian National Research Ethics Commission (CONEP/Brazil), under protocol number 53017321.0.0000.0096, and was conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eConflict of Interest Disclosure\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare no conflicts of interest.\u003c/p\u003e\n\u003cp\u003eBiometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWyci\u0026acute;slik L, Wyci\u0026acute;slik P, Momot A. 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Developmental Basis of Sexually Dimorphic Digit Ratios. Proc Natl Acad Sci USA. 2011;108(39):16289-16294.\u003c/li\u003e\n\u003cli\u003eFBI Biometric Specifications. https://fbibiospecs.fbi.gov/biometric-specifications-1-1/document-library.\u003c/li\u003e\n\u003cli\u003eNIST (2021). Fingerprint Image Quality Standards for Neonatal Biometrics. National Institute of Standards and Technology Report.\u003c/li\u003e\n\u003cli\u003eJain AK, Ross A, Prabhakar S. Fingerprint Matching Using Minutiae and Texture Features. Int\u0026rsquo;l Conference on Image Processing (ICIP), pp.282-285, Thessaloniki, Greece, Oct 7 - 10, 2001.\u003c/li\u003e\n\u003cli\u003eJain AK, Feng J. Latent Fingerprint Matching. IEEE Trans Pattern Anal Mach Intell. 2011;33(1):88-100.\u003c/li\u003e\n\u003cli\u003eNel S, de Man J, van den Berg L, Wenhold FAM. Statistical Assessment of Reliability of Anthropometric Measurements in the Multi-Site South African National Dietary Intake Survey 2022. Eur J Clin Nutr. 2024;78(11):1005-1113.\u003c/li\u003e\n\u003cli\u003eStomfai S, Ahrens W, Bammann K, Kov\u0026aacute;cs E, S, N, et al. Intra-And Inter-Observer Reliability in Anthropometric Measurements in Children. Int J Obes. 2011;35(S1):S45-51.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"newborn, anthropometry, fingerprints, personal identification, biometry","lastPublishedDoi":"10.21203/rs.3.rs-6503555/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6503555/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo measure the 1st to 5th digits, palmar, hallucal, and heel regions of full-term newborns to define anatomical reference values for neonatal biometric device design.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy Design\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA cross-sectional study conducted at a public university hospital in southern Brazil. Anthropometric measurements were obtained bilaterally from 34 full-term newborns (39–41 weeks gestation) using a precision digital caliper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResult\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe mean length of the 2nd to 5th digits was 9.23 ± 0.58 mm, with no significant differences by side or sex. The 1st digit was consistently longer (p \u0026lt; 0.01), and the 2nd digit was slightly longer in males (p = 0.04). Palmar, hallucal, and heel measurements showed no significant variation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe thumb is the most favorable site for fingerprint capture. The findings provide foundational data for the development of safe and effective neonatal biometric technologies and support equitable identification from birth, aligning with SDG 16.9 of the United Nations.\u003c/p\u003e","manuscriptTitle":"Biometric Foundations for Newborn Identification: Anatomical Finger and Foot Measurements in Full-Term Neonates","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-08 20:23:14","doi":"10.21203/rs.3.rs-6503555/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"44096b30-b826-4a2b-8599-0c10d72f137b","owner":[],"postedDate":"May 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":47876263,"name":"Scientific community and society/Developing world"},{"id":47876264,"name":"Scientific community and society/Scientific community"}],"tags":[],"updatedAt":"2025-05-27T12:26:50+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-08 20:23:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6503555","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6503555","identity":"rs-6503555","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}