From CRONOS to CRONOS-Kids: Investigating Neurological Development in Toddlers After Maternal SARS-CoV-2 Infection During Pregnancy – A Study Protocol For A Prospective Cohort Study

From CRONOS to CRONOS-Kids: Investigating Neurological Development in Toddlers After Maternal SARS-CoV-2 Infection During Pregnancy – A Study Protocol For A Prospective Cohort Study | 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 Research Article From CRONOS to CRONOS-Kids: Investigating Neurological Development in Toddlers After Maternal SARS-CoV-2 Infection During Pregnancy – A Study Protocol For A Prospective Cohort Study Nadine Mand, Franziska König, Mirjam Wege, Anna-Lena Cares, Tamée Ersfeld, and 13 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8295431/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 Purpose Infection with SARS-CoV-2 during pregnancy increases the risk for adverse events in mothers and their newborns. Research is increasingly exploring the potential consequences of intrauterine exposure to the developing nervous system. However, there is still a lack of high-quality studies on long-term outcomes. The CRONOS-Kids study aims to investigate the global development of children after exposure to SARS-CoV-2 in utero in comparison to an unexposed control group. This paper outlines the CRONOS-Kids study protocol. Methods The study is designed as a prospective population-based cohort study, and will recruit children aged 36–60 months at the time of assessment. The exposed cohort will be recruited from the German CRONOS registry and will only include participants who have been exposed to the Alpha and Delta variants of SARS-CoV-2. The unexposed cohort will be recruited by local paediatricians and via social media. For clinical evaluations, the Movement Assessment Battery for Children 2nd Edition will be used. Parental self-reports on development will use the Ages and Stages Questionnaire 3rd Edition. Additional questionnaires cover general information about maternal and child health, vaccinations, healthcare usage, media consumption, maternal quality of life, and social status. Results Until December 2025, we aim to recruit 125 exposed and 125 unexposed children across five study sites. Conclusion The CRONOS-Kids study will explore the impact of intrauterine SARS-CoV-2 exposure of specific virus variants on long-term neurologic outcomes in children, as well as the broader consequences of the pandemic. Trial registration The study was registered at clinicaltrials.gov in April 2025 (NCT06968897). SARS-CoV-2 pregnancy child development What is Known SARS-CoV-2 infection during pregnancy increases the risk of adverse outcomes in mothers and their newborns. Studies investigating the influence of intrauterine SARS-CoV-2 exposure on neurodevelopment of children have produced equivocal results. What is New This is the first national prospective cohort study on the long-term outcome of children exposed to specific variants of SARS-CoV-2 in utero and, to our knowledge, the first cohort study to clinically assess gross and fine motor development and screen for cognitive as well as social-emotional development in this context. Introduction SARS-CoV-2 infection during pregnancy has been shown to increase the risk of severe maternal COVID-19, stillbirth, and preterm delivery [1-6]. Subsequent neonatal SARS-CoV-2 infection is rather rare, typically presenting asymptomatically, and mostly acquired during the postnatal period [7-9]. Although predominantly affecting the pulmonary system, SARS-CoV-2 is a virus with multisystemic symptoms, including neurological manifestations. Neurological symptoms are often nonspecific, such as lethargy or hyperexcitability in infants and headache and myalgia in older children. Other symptoms, such as encephalitis or seizures, occur mainly in severely ill or already neurologically compromised children [10-13]. Several studies have discussed the potential effects of SARS-CoV-2 on brain development, particularly in cases of intrauterine exposure [14-16]. Potential mechanisms by which the virus could affect infant development are either a direct impact of the virus due to transplacental SARS-CoV-2 transmission, through maternal and secondary fetal immune activation, or in the context of virus-induced pregnancy complications, such as premature births [17, 18]. Studies investigating intrauterine SARS-CoV-2 exposure have produced equivocal results. Several have demonstrated the presence of neurological abnormalities in newborns and infants following in utero exposure to SARS-CoV-2 or postnatal SARS-CoV-2 infection [14, 19-22]. Other studies have not identified a clear association [23-25]. These controversial results could be explained by variability in sample size and study quality. Furthermore, details of the control group have been documented inconsistently [26-28]. Most prospective investigations were based on parental questionnaires and reported concerns about the infant’s neurodevelopment [21, 22, 25, 29]. Standardized clinical assessments have been carried out rarely, and if so, solely on infants [14]. To date, only three studies report on outcomes in older children, using parental self-reporting in 24-month-old children [25, 30, 31]. Previously, no study has distinguished between the intrauterine exposures of different SARS-CoV-2 variants of concern (VOC). In contrast to the wildtype and the Omicron variant, infections with the Alpha and Delta variants have been associated with a higher rate of placentitis and a concomitant increased risk of stillbirth and preterm delivery [32-34], thus possibly impacting fetal and neonatal neurodevelopment to a greater degree than the other variants. As there is a need for screening for long-term neurodevelopmental deficits of children who were exposed to SARS-CoV-2 prenatally, we have established this multisite national initiative based on the COVID-19 Related Obstetric and Neonatal Outcome Study (CRONOS) [35, 36]. We hypothesize that prenatal exposure to the Alpha and Delta variants increases the risk for neurodevelopmental disorders in terms of changes in motor development, social-emotional development, problem-solving, and communication skills in toddlers and preschoolers. In addition, we assess the same parameters of neurodevelopment in an unexposed control group, thereby also investigating collateral effects of the pandemic on mothers and their offspring. Study aims and objectives The present study aims to investigate the neurodevelopmental effects of intrauterine SARS-CoV-2 exposure on children aged 36 to 60 months and to compare the results to an unexposed age-matched control group born in the same time frame. Primary outcome measures are Clinical assessment of motor skills using the Movement Assessment Battery for Children 2 nd Edition (M-ABC-2) Secondary outcome measures are Screening for global development in terms of communication, problem-solving, and social-emotional skills using the Ages and Stages Questionnaire 3 rd Edition (ASQ-3) Timing of vaccinations and preventive medical examinations Healthcare system usage in the first year of life Methods Study design and participants The study is designed as a prospective population-based cohort study, with participants recruited from the ages of 36 to 60 months at the time of assessment. The identification of exposed children will be conducted through the CRONOS registry. A control group will be recruited through local paediatric practices and targeted outreach via social media platforms (Instagram, LinkedIn, and WhatsApp). Data collection will comprise the administration of questionnaires, including parental self-report measures, in addition to clinical assessments conducted by researchers who are unaware of the children's exposure status. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist will guide reporting [37]. Setting CRONOS (COVID-19 Related Obstetric and Neonatal Outcome Study) was a prospective German registry including women with SARS-CoV-2 infection during their pregnancy, with 130 obstetric hospitals actively participating, comprising one-third of all German births [36]. Between April 2020 and February 2023, more than 8500 women and their newborns were included [7]. Maternal SARS-CoV-2 infection was defined as a detection of viral RNA by PCR testing of a nasopharyngeal or oropharyngeal swab, regardless of symptoms or symptom severity, or detection of SARS-CoV-2 antibodies in an antibody-based serum assay in symptomatic women. In the case of PCR testing, some hospitals differentiated between variants of concern (VOC). If this information was not available, the most likely VOC was assigned to the case depending on the time of infection, with the wildtype virus being predominant till February 2021, Alpha from March 2021 to July 2021, Delta from August 2021 to December 2021, and Omicron since January 2022 [38]. In addition to the CRONOS-Kids principal investigator's research team, four university hospitals were selected as consortium partners based on their previous recruitment rates in the CRONOS registry and the number of eligible patients. Sampling and recruitment Exposure cohort As the objective of the study is to assess the possible impact of the Alpha and Delta variants on the neurodevelopment of the offspring, families are eligible for study inclusion when the pregnant woman was infected between 01.03.2021 and 31.12.2021, or when infection with Alpha or Delta was confirmed via PCR test, regardless of the timing of infection. Pregnant women are required to have agreed during initial enrolment in CRONOS to be re-contacted. After identifying eligible women by the CRONOS study centre, families are contacted by the local study sites and invited to participate in the CRONOS-Kids study. Unexposed control group A cohort of children without known or documented intrauterine exposure to SARS-CoV-2 is recruited using probability sampling. Local paediatricians in outpatient practices are invited to provide study information to families during routine preventive medical exams, which are mandatory for four-year-old children in Germany. Additional recruitment efforts include the dissemination of study materials through local kindergartens and nurseries, as well as via personal networks. To enhance public engagement, a dedicated Instagram account featuring a study mascot (@cronos_kids) has been established to share information about the study with a broader audience. A potential SARS-CoV-2 infection in childhood will be recorded in both groups and considered in secondary analyses. Written consent is obtained from all participants. Recruitment Recruitment started on 1 April 2025 and will continue through December 2025. Families interested in participating are invited to contact the CRONOS-Kids coordinating team via the official study website (http://cronos-kids.de) to schedule an appointment at one of the five study sites. Pseudonymisation is carried out centrally by the coordination team using an eight-digit code. The research team conducting developmental assessments remains blinded to the exposure status of the children, as they do not have access to the pseudonymization key. Parents accompanying the children are informed of the blinding procedure and asked not to disclose any information regarding SARS-CoV-2 infection during pregnancy. We aim to recruit at least 125 children who were exposed in utero and 125 unexposed children. Sample size calculation We calculated that 64 patients per group are needed, i.e., 128 patients in total, to detect a difference of 0.5 standard deviation in an unpaired t-test in mean M-ABC-2 total scores (Cohen’s d = 0.5), with an alpha level of 0.05 and a power of 0.8 [39]. Exclusion criteria Children with major congenital anomalies, regardless of intrauterine infection status, are excluded from analysis. Children are eligible for assessment regardless of whether they are preterm or not singletons. Study instruments Primary Outcome The primary objective of this study is to clinically assess the motor skills of all participating children. For this, the M-ABC-2 will be used [40]. It consists of three movement domains: manual dexterity (MD), aiming and catching (AC), and balance (B), with two (AC) or three (MD and B) different tasks each. There are three age bands available, the first (3 to 6 years) being used in this study. The M-ABC-2 was chosen because of its validation in Western European children, including German children, the availability of a German translation, an appropriate age range, internal reliability (r=.97), and short administration time (20 to 30 minutes). We will use the total score as the primary outcome. The total score ranges from 14 to ≥108 (total scores above 108 points do not result in further improvement of the percentile rank). Rater training was provided prior to the start of the study, based on a previously published rater training programme for the assessment of observations [41] using a four-step approach: 1. Conveying expertise: Expertise in child development was provided by shadowing paediatricians in outpatient care and by accompanying psychologists and physiotherapists in developmental assessments. 2. Self-study: The research team familiarised themselves with the assessment tool and the theoretical aspects of rater error. 3. First assessment with experts: The research team shadowed experts as they performed two clinical assessments using the M-ABC-2 and simultaneously scored the results with the experts. 4. Pilot testing: Two clinical assessments and consecutive scoring were conducted by the research team under the supervision of experts. All consecutive tests are performed by the same research team to ensure a high interrater reliability. Secondary Outcome To screen global development, the age-appropriate questionnaires of the ASQ-3 will be used. Each questionnaire contains five domains: communication, gross motor, fine motor, problem-solving, and personal-social development, with six questions each. Every question can be rated according to the child’s abilities with “yes”, “sometimes”, and “not yet”, scored 10, 5, or 0 points, respectively. Each domain is analysed separately with total scores ranging from 0 to 60. Age-specific thresholds are defined and validated, indicating potentially increased risk for neurodevelopmental delay [42]. For screening social-emotional skills, the parent questionnaire for supplementary developmental assessment (EEE - “Elternfragebogen zur ergänzenden Entwicklungsbeurteilung”) will be used [43]. The EEE can be used in preventive medical examinations (PMEs) that are mandatory in Germany at different ages of a child [44]. They compile specific sets of social-emotional and practical life skills that are expected to be acquired at that age. Each EEE comprises a different number of questions, ranging from 27 (10 to 12 months) to 35 (60 to 64 months), which can be rated with “yes” or “no”. A web-based general questionnaire was developed on REDCap (Research Electronic Data Capture) [45, 46], comprising sections on current and previous pregnancies, birth, child health, postnatal SARS-CoV-2 infection, the child´s media consumption, the maternal quality of life, socioeconomic status, and social desirability. Questions on pregnancy and birth focus on potential confounders of child development, such as pre-existing maternal illness, smoking, drug use, and preterm birth. Questions on child health include postnatal complications, feeding practices, and health care visits. Socioeconomic status is measured using a multidimensional index score consisting of three metric components: education and occupational qualification, occupational status, and net income [47]. The German version of the EuroQoL quality of life questionnaire (EQ-5D-5L) is used to evaluate the perceived quality of life at the time of the analysis [48]. To assess potential confounding in self-reported outcomes, we included questions on social desirability using the SDS-CM scale, consisting of 23 items [49]. Timing of vaccinations and PMEs will be extracted from official vaccination certificates and specific PME documents (so-called “U-Heft”) and entered into a designated web-based database. Data collection Data will be solely collected by the Marburg University research team on all study sites, thus ensuring a high internal consistency. ASQ-3 and EEE questionnaires are sent to parents at least one week before their clinical appointments, thus allowing time for self-assessing their children. At the time of clinical assessment, M-ABC-2 will be performed by the research team, blinded to the exposure status of the children. ASQ-3 and EEE questionnaires are collected and checked for completeness. The general questionnaire will be completed during the clinical assessment using a dedicated CRONOS-Kids study tablet (Microsoft Surface 2.0). Data on vaccination and PMEs are also collected on this study tablet. Bias A potential sampling bias is anticipated, as families with higher educational levels and German language proficiency may be more likely to participate in the study. However, since this tendency is expected in both the exposed and unexposed groups, and detailed information on socioeconomic status is being collected, potential confounding will be addressed through statistical adjustment. To minimize performance and observer bias, the research team conducting the assessments is separate from the coordination team responsible for recruitment and appointment logistics. Furthermore, accompanying parents are instructed not to reveal any information regarding SARS-CoV-2 infection during pregnancy to ensure assessor blinding. Ethics approval, funding, and registration The study was approved by the ethics committee of Marburg University (AZ 114/22), as well as the ethics committees at the local study sites. Research will be conducted in accordance with the Declaration of Helsinki. Funding was provided by the German Society for Perinatal Medicine (DGPM, https://www.dgpm-online.org/). The study was registered at clinicaltrials.gov in April 2025 (NCT06968897). Statistical analysis The Marburg University research team will be responsible for data acquisition and validation, and conducting the statistical analysis. The cohort’s baseline sociodemographic and clinical characteristics will be compared between the exposure and unexposed control cohorts using appropriate tests depending on variable categories: chi-square tests will be used for categorical variables, and t-tests for continuous variables. There will be no adjustments for study sites. Logistic regression models will be employed to examine the exposure status and total scores in M-ABC-2, ASQ-3, and the EEE. Adjusting for potential confounders is planned for maternal age, social status, parental education, children's sex, and gestational age of delivery. Further analysis on ASQ-3 and EEE-scores will include social desirability measured by the SDS-CM scale as a potential confounder. An exploratory subgroup analysis will be performed for the trimester of infection, infection severity, maternal quality of life, and duration of breastfeeding. The timing of vaccinations and PMEs will be analysed descriptively, as well as the healthcare system usage in the first year of life. We will summarise the amount of missing data in each of the variables for both cohorts separately. Cohorts will be compared using complete cases for the specific outcome parameter. Based on the proposed data collection, we expect the proportion of missing data to be small. In case of a high amount of missing data, we may consider multiple imputation as a sensitivity analysis. P values <.05 will be considered statistically significant. For all analyses, the statistical software SPSS (IBM Corp., Armonk, NY, USA) will be used. Discussion To our knowledge, this is the first prospective cohort study to clinically assess neurodevelopment in 3 to 5-year-old children after intrauterine exposure to the Alpha or Delta variant of SARS-CoV-2. We will conduct a multicentre cohort study based on the CRONOS registry using a carefully designed set of study instruments developed within the CRONOS-Kids study group, incorporating two internationally recognized and validated tools. Furthermore, the exposed children will be compared to a control group of unexposed children of the same age, controlling for potential confounding parameters. Clinical standardized assessments have been rarely used in previous studies investigating the effects of intrauterine exposure to SARS-CoV-2 on children, especially not in children older than 12 months [ 14 ]. These will be conducted by specifically trained researchers in this study to minimize the possibility of confounding bias. Furthermore, we will systematically examine social desirability, a potential confounding factor in parental assessments of children's development. We will exclude children who were exposed to the wildtype or Omicron variant in utero. Previous research on intrauterine exposure to SARS-CoV-2 has yielded inconsistent findings, potentially due to the failure to distinguish between different viral variants. Given that the Alpha and Delta variants have been associated with an elevated risk of stillbirth, preterm birth, placentitis, and neonatal SARS-CoV-2 infection [ 32 – 34 ], their impact on fetal neurodevelopment may be more pronounced than that of the wildtype or Omicron variant. Moreover, since neurodevelopmental delay is generally uncommon, aggregating data from multiple virus variants may obscure potential differences in their effects. Conclusion The findings of this study will contribute to a more comprehensive understanding of the long-term postnatal effects of SARS-CoV-2 infection during pregnancy, as well as the broader consequences of the pandemic, including social isolation or reduced access to healthcare. A better understanding of these factors could improve care for children exposed to the virus in utero. Insights gained from the long-term effects of SARS-CoV-2 infection and pandemic disruptions could help to prepare for future crises, ensuring better maternal and child health. Declarations Consent to participate Participating parents will provide written consent. Consent to Publish Not applicable. References Zambrano, L.D., et al., Update: Characteristics of Symptomatic Women of Reproductive Age with Laboratory-Confirmed SARS-CoV-2 Infection by Pregnancy Status - United States, January 22-October 3, 2020. MMWR Morb Mortal Wkly Rep, 2020. 69 (44): p. 1641-1647. Sitter, M., et al., Pregnant and Postpartum Women Requiring Intensive Care Treatment for COVID-19-First Data from the CRONOS-Registry. J Clin Med, 2022. 11 (3). Boettcher, L.B. and T.D. Metz, Maternal and neonatal outcomes following SARS-CoV-2 infection. Semin Fetal Neonatal Med, 2023. 28 (1): p. 101428. Allotey, J., et al., Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and meta-analysis. Bmj, 2020. 370 : p. m3320. Iannaccone, A., et al., Is the risk of still and preterm birth affected by the timing of symptomatic SARS-CoV-2 infection during pregnancy? Data from the COVID-19 Related Obstetrics and Neonatal Outcome Study Network, Germany. Am J Obstet Gynecol, 2023. 228 (3): p. 351-352.e2. Wei, S.Q., et al., The impact of COVID-19 on pregnancy outcomes: a systematic review and meta-analysis. Cmaj, 2021. 193 (16): p. E540-e548. Mand, N., et al., Vertical transmission of SARS-CoV-2 - data from the German COVID-19 related obstetric and neonatal outcome study (CRONOS). J Perinat Med, 2024. Al-Lawama, M., et al., Perinatal Transmission and Clinical Outcomes of Neonates Born to SARS-CoV-2-Positive Mothers. J Clin Med Res, 2021. 13 (8): p. 420-424. De Luca, D., et al., Transmission of SARS-CoV-2 from mother to fetus or neonate: What to know and what to do? Semin Fetal Neonatal Med, 2023. 28 (1): p. 101429. Stafstrom, C.E., Neurological effects of COVID-19 in infants and children. Dev Med Child Neurol, 2022. 64 (7): p. 818-829. Doenhardt, M., et al., Epidemiology of 7375 children and adolescents hospitalized with COVID-19 in Germany, reported via a prospective, nationwide surveillance study in 2020-2022. Sci Rep, 2024. 14 (1): p. 47. LaRovere, K.L., et al., Neurologic Involvement in Children and Adolescents Hospitalized in the United States for COVID-19 or Multisystem Inflammatory Syndrome. JAMA Neurol, 2021. 78 (5): p. 536-547. Raschetti, R., et al., Synthesis and systematic review of reported neonatal SARS-CoV-2 infections. Nat Commun, 2020. 11 (1): p. 5164. Aldrete-Cortez, V., et al., Infants prenatally exposed to SARS-CoV-2 show the absence of fidgety movements and are at higher risk for neurological disorders: A comparative study. PLoS One, 2022. 17 (5): p. e0267575. Joma, M., et al., COVID-19 and Pregnancy: Vertical Transmission and Inflammation Impact on Newborns. Vaccines (Basel), 2021. 9 (4). Shook, L.L., et al., COVID-19 in pregnancy: implications for fetal brain development. Trends Mol Med, 2022. 28 (4): p. 319-330. Brum, A.C. and N.E. Vain, Impact of perinatal COVID on fetal and neonatal brain and neurodevelopmental outcomes. Semin Fetal Neonatal Med, 2023. 28 (2): p. 101427. Dubey, H., et al., SARS-CoV-2 (COVID-19) as a possible risk factor for neurodevelopmental disorders. Front Neurosci, 2022. 16 : p. 1021721. Ayed, M., et al., Neurodevelopmental outcomes of infants born to mothers with SARS-CoV-2 infections during pregnancy: a national prospective study in Kuwait. BMC Pediatr, 2022. 22 (1): p. 319. Edlow, A.G., et al., Neurodevelopmental Outcomes at 1 Year in Infants of Mothers Who Tested Positive for SARS-CoV-2 During Pregnancy. JAMA Netw Open, 2022. 5 (6): p. e2215787. Hill, R.A., et al., Investigating the impact of severe maternal SARS-CoV-2 infection on infant DNA methylation and neurodevelopment. Mol Psychiatry, 2025. 30 (5): p. 1976-1984. Wang, Y., et al., Impact of Covid-19 in pregnancy on mother's psychological status and infant's neurobehavioral development: a longitudinal cohort study in China. BMC Med, 2020. 18 (1): p. 347. Shuffrey, L.C., et al., Association of Birth During the COVID-19 Pandemic With Neurodevelopmental Status at 6 Months in Infants With and Without In Utero Exposure to Maternal SARS-CoV-2 Infection. JAMA Pediatr, 2022. 176 (6): p. e215563. Firestein, M.R., et al., Assessment of Neurodevelopment in Infants With and Without Exposure to Asymptomatic or Mild Maternal SARS-CoV-2 Infection During Pregnancy. JAMA Netw Open, 2023. 6 (4): p. e237396. Jaswa, E.G., et al., In Utero Exposure to Maternal COVID-19 and Offspring Neurodevelopment Through Age 24 Months. JAMA Netw Open, 2024. 7 (10): p. e2439792. Hessami, K., et al., COVID-19 Pandemic and Infant Neurodevelopmental Impairment: A Systematic Review and Meta-analysis. JAMA Netw Open, 2022. 5 (10): p. e2238941. Pinheiro, G., et al., Effects of intrauterine exposure to SARS-CoV-2 on infants' development: a rapid review and meta-analysis. Eur J Pediatr, 2023. 182 (5): p. 2041-2055. Jackson, R., et al., Antenatal and neonatal exposure to SARS-CoV-2 and children's development: a systematic review and meta-analysis. Pediatr Res, 2024. 96 (1): p. 40-50. Hardie, I., et al., Early childhood developmental concerns following SARS-CoV-2 infection and COVID-19 vaccination during pregnancy: a Scottish population-level retrospective cohort study. Lancet Child Adolesc Health, 2025. 9 (3): p. 162-171. Jackson, R., et al., Association of antenatal or neonatal SARS-COV-2 exposure with developmental and respiratory outcomes, and healthcare usage in early childhood: a national prospective cohort study. EClinicalMedicine, 2024. 72 : p. 102628. Vrantsidis, D.M., et al., Neurodevelopment in the First 2 Years of Life Following Prenatal Exposure to Maternal SARS-CoV-2 Infection. JAMA Netw Open, 2024. 7 (11): p. e2443697. Fitzgerald, B., et al., Fetal Deaths in Ireland Due to SARS-CoV-2 Placentitis Caused by SARS-CoV-2 Alpha. Arch Pathol Lab Med, 2022. 146 (5): p. 529-537. Merriel, A., B. Fitzgerald, and K. O'Donoghue, SARS-CoV-2-Placental effects and association with stillbirth. Bjog, 2024. 131 (4): p. 385-400. Stenton, S., et al., SARS-COV2 placentitis and pregnancy outcome: A multicentre experience during the Alpha and early Delta waves of coronavirus pandemic in England. EClinicalMedicine, 2022. 47 : p. 101389. Pecks, U., et al., Pregnancy and SARS-CoV-2 Infection in Germany-the CRONOS Registry. Dtsch Arztebl Int, 2020. 117 (49): p. 841-842. Pecks, U., et al., SARS-CoV-2 Infection During Pregnancy. Dtsch Arztebl Int, 2022. 119 (35-36): p. 588-594. von Elm, E., et al., The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol, 2008. 61 (4): p. 344-9. Schillung J, B.S., Tolksdorf K, Zweite Aktualisierung der „Retrospektiven Phaseneinteilung der COVID-19-Pandemie in Deutschland“. Epid Bull, 2022. 10 : p. 3-5. Faul, F., et al., G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods, 2007. 39 (2): p. 175-91. Petermann, F., Bös, K., & Kastner, J, Movement Assessment Battery for Children - Second Edition. Deutsche Bearbeitung . 4., überarbeitete und erweiterte Auflage ed. 2015: Pearson. Mand, N., et al., Successful implementation of a rater training program for medical students to evaluate simulated pediatric emergencies. GMS J Med Educ, 2023. 40 (4): p. Doc47. Squires, J., & Bricker, D., Ages & Stages Questionnaires®, Third Edition (ASQ-3™): A Parent-Completed Child Monitoring System. 2009, Baltimore Paul H. Brookes Publishing Co., Inc. Petermann, F. and T. Macha, Elternfragebögen zur ergänzenden Entwicklungsbeurteilung bei den kinderärztlichen Vorsorgeuntersuchungen U6 bis U9: EEE U6-U9 . 2003: Swets Test Services. Schmidtke C, K.B., Starker A, Lampert T (Robert Koch-Institut), Inanspruchnahme der Früherkennungsuntersuchungen für Kinder in Deutschland – Querschnittergebnisse aus KiGGS Welle 2. Journal of Health Monitoring, 2018. 3 (3). Harris, P.A., et al., Research electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform, 2009. 42 (2): p. 377-81. Harris, P.A., et al., The REDCap consortium: Building an international community of software platform partners. J Biomed Inform, 2019. 95 : p. 103208. Lampert, T., et al., Messung des sozioökonomischen Status in der KiGGS-Studie. Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz, 2014. 57 (7): p. 762-770. Herdman, M., et al., Development and preliminary testing of the new five-level version of EQ-5D (EQ-5D-5L). Qual Life Res, 2011. 20 (10): p. 1727-36. Lück, H., Timaeus E., Soziale Erwünschtheit (SDS-CM) . 2014: Zusammenstellung sozialwissenschaftlicher Items und Skalen (ZIS). Additional Declarations The authors declare no competing interests. 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8295431","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":556264171,"identity":"40b89d04-eeaf-4f26-aa36-2aaca873aab2","order_by":0,"name":"Nadine Mand","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYJACCYYKIMl88AGYDQRsEPED+LScAWK2ZAMStDC2wbUwENai23724O3CeXV1/G3MDMy8OyxAIs8e8+6pZeA73oBVi9mZvGTrmdsOS0gcA2k5IwEUSTc35nl2nEHyDHZrzA7kmEnzbjsgwXC//wAzb5tE/bYDaWzSPAeOMRjcSMCu5fwboJY5dRLyYFvagLacfwbVcv8Bdi03QLY0MEsYwLXcANtSA7QFu/fNbrwxtuY5dlhyI1DLwblgLc/YDeccOMAjeQaXw3IMb/PU1PHLHWNmfPC2rQ4oksb24M2BOjm+49i9jwKQlRzmIaweDdSRrGMUjIJRMAqGLQAAIjlabflm/NgAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-5973-3311","institution":"Marburg University, Faculty of Medicine, Neonatology and Pediatric Intensive Care, Department of Paediatrics, Marburg, Germany","correspondingAuthor":true,"prefix":"","firstName":"Nadine","middleName":"","lastName":"Mand","suffix":""},{"id":556264172,"identity":"908054f8-c524-40c2-b238-3ff150d0a93b","order_by":1,"name":"Franziska König","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Neonatology and Pediatric Intensive Care, Department of Paediatrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Franziska","middleName":"","lastName":"König","suffix":""},{"id":556264173,"identity":"7bfd2a55-efc2-4103-876b-0b82f88556db","order_by":2,"name":"Mirjam Wege","email":"","orcid":"https://orcid.org/0000-0001-7390-0999","institution":"Marburg University, Faculty of Medicine, Department of Paediatrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Mirjam","middleName":"","lastName":"Wege","suffix":""},{"id":556264174,"identity":"8e11a212-0611-4dab-8286-8f4d489d47cb","order_by":3,"name":"Anna-Lena Cares","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Anna-Lena","middleName":"","lastName":"Cares","suffix":""},{"id":556264175,"identity":"02661642-f7d3-49e7-af60-e9465d902cf6","order_by":4,"name":"Tamée Ersfeld","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Tamée","middleName":"","lastName":"Ersfeld","suffix":""},{"id":556264176,"identity":"4ebc2b12-b2c5-4c2b-8249-47ec838a8c50","order_by":5,"name":"Ines Wallot","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Neonatology and Pediatric Intensive Care, Department of Paediatrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Ines","middleName":"","lastName":"Wallot","suffix":""},{"id":556264177,"identity":"fe1ab4af-9a9b-4215-998d-34ec1594db34","order_by":6,"name":"Charlotte Hahn","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Neonatology and Pediatric Intensive Care, Department of Paediatrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Charlotte","middleName":"","lastName":"Hahn","suffix":""},{"id":556264178,"identity":"51ab407c-68e7-459b-9c2f-acbd007a78d2","order_by":7,"name":"Corinna Keil","email":"","orcid":"","institution":"Marburg University, Faculty of Medicine, Clinic of Gynaecology and Obstetrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Corinna","middleName":"","lastName":"Keil","suffix":""},{"id":556264179,"identity":"ddfdaade-3397-4b5d-a957-eb6abee5e884","order_by":8,"name":"Janine Zöllkau","email":"","orcid":"https://orcid.org/0000-0002-1008-3714","institution":"Jena University Hospital, Department of Obstetrics, Jena, German","correspondingAuthor":false,"prefix":"","firstName":"Janine","middleName":"","lastName":"Zöllkau","suffix":""},{"id":556264180,"identity":"9ceb8c51-5722-4afa-9e40-34a4ae6d5f4a","order_by":9,"name":"Daniela Steuernagel","email":"","orcid":"","institution":"Jena University Hospital, Neuropaediatrics, Department of Paediatrics, Jena, Germany","correspondingAuthor":false,"prefix":"","firstName":"Daniela","middleName":"","lastName":"Steuernagel","suffix":""},{"id":556264181,"identity":"b40d05fd-735b-4c02-a7b1-c2711f75e368","order_by":10,"name":"Mirjam Kunze","email":"","orcid":"","institution":"Department of Obstetrics and Gynaecology, University Medical Centre, Medical Faculty, University of Freiburg, Freiburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Mirjam","middleName":"","lastName":"Kunze","suffix":""},{"id":556264182,"identity":"266454cb-df66-426b-a544-0e94e10b13f2","order_by":11,"name":"Martin Kuntz","email":"","orcid":"https://orcid.org/0000-0002-8231-2838","institution":"Department of General Paediatrics, Adolescent Medicine and Neonatology, Medical Centre – University of Freiburg / Medical Faculty – University of Freiburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Martin","middleName":"","lastName":"Kuntz","suffix":""},{"id":556264183,"identity":"c12e9ce7-aec6-4cb5-890a-13c98bd8f3a3","order_by":12,"name":"Kristin Andresen","email":"","orcid":"https://orcid.org/0009-0004-5935-0571","institution":"University of Schleswig-Holstein, Department of Obstetrics and Gynaecology, Kiel, Germany","correspondingAuthor":false,"prefix":"","firstName":"Kristin","middleName":"","lastName":"Andresen","suffix":""},{"id":556264184,"identity":"74e6c28a-e6d1-4855-b8a4-86c335766118","order_by":13,"name":"Ann-Carolin Longardt","email":"","orcid":"https://orcid.org/0009-0004-4764-2817","institution":"University of Schleswig-Holstein, Department for Neonatology, Pediatric Pneumology and Neuropaediatrics","correspondingAuthor":false,"prefix":"","firstName":"Ann-Carolin","middleName":"","lastName":"Longardt","suffix":""},{"id":556264185,"identity":"50cd72d0-b15f-44c8-9724-69648dc37133","order_by":14,"name":"Lars Mense","email":"","orcid":"https://orcid.org/0000-0002-2586-8987","institution":"Saxonian Centre for Feto/Neonatal Health, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany","correspondingAuthor":false,"prefix":"","firstName":"Lars","middleName":"","lastName":"Mense","suffix":""},{"id":556264186,"identity":"3e217836-810d-4c89-99ef-ea7c11b8a386","order_by":15,"name":"Ulrich Pecks","email":"","orcid":"https://orcid.org/0000-0002-0784-1262","institution":"Department of Obstetrics, University of Würzburg, Würzburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Ulrich","middleName":"","lastName":"Pecks","suffix":""},{"id":556264187,"identity":"7fd8faeb-5723-44f7-b6ef-3307661e7c5e","order_by":16,"name":"Mario Rüdiger","email":"","orcid":"https://orcid.org/0000-0001-7498-1209","institution":"Saxonian Centre for Feto/Neonatal Health, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany","correspondingAuthor":false,"prefix":"","firstName":"Mario","middleName":"","lastName":"Rüdiger","suffix":""},{"id":556264188,"identity":"476238ad-b9b3-43bb-8289-28bc74a17a50","order_by":17,"name":"Stefanie Weber","email":"","orcid":"https://orcid.org/0000-0002-9498-2337","institution":"Marburg University, Department of Paediatrics, Marburg, Germany","correspondingAuthor":false,"prefix":"","firstName":"Stefanie","middleName":"","lastName":"Weber","suffix":""}],"badges":[],"createdAt":"2025-12-06 14:50:49","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":true,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-8295431/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8295431/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":97896628,"identity":"f5ae0310-3c76-4410-96dd-54f38236a279","added_by":"auto","created_at":"2025-12-10 15:36:49","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":142904,"visible":true,"origin":"","legend":"","description":"","filename":"MandFromCRONOStoCRONOSKids.docx","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/f21039392ea1d56b8df52a40.docx"},{"id":97759839,"identity":"a14c2895-7490-4d14-b7d0-8a132c5265b8","added_by":"auto","created_at":"2025-12-09 05:31:36","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":342,"visible":true,"origin":"","legend":"","description":"","filename":"rs8295431.json","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/f8691689b578fb7f45010d53.json"},{"id":97759840,"identity":"aa5eb670-0d3f-42fd-83a5-ba3f95439fe1","added_by":"auto","created_at":"2025-12-09 05:31:36","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":98904,"visible":true,"origin":"","legend":"","description":"","filename":"rs82954310enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/10c68ecb75336c1f49bdb0bb.xml"},{"id":97896337,"identity":"f9199fc9-9985-437e-ac3e-b8b1f5505b6c","added_by":"auto","created_at":"2025-12-10 15:36:23","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":95675,"visible":true,"origin":"","legend":"","description":"","filename":"rs82954310structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/2fe26262bb3bbaaf5bf7a5a1.xml"},{"id":97896103,"identity":"26f8746a-526c-41a6-bf32-de3cc9d1d30c","added_by":"auto","created_at":"2025-12-10 15:35:53","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":113928,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/8abbb36744789b8ecf43376b.html"},{"id":97902675,"identity":"fd2a8cff-bc67-4fd1-ad03-9566a9b05b94","added_by":"auto","created_at":"2025-12-10 15:53:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":546563,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8295431/v1/e10abe9d-1f80-4160-8f01-d903c4eb9be2.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eFrom CRONOS to CRONOS-Kids: Investigating Neurological Development in Toddlers After Maternal SARS-CoV-2 Infection During Pregnancy – A Study Protocol For A Prospective Cohort Study\u003c/p\u003e","fulltext":[{"header":"What is Known ","content":"\u003cul\u003e\n \u003cli\u003eSARS-CoV-2 infection during pregnancy increases the risk of adverse outcomes in mothers and their newborns. \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eStudies investigating the influence of intrauterine SARS-CoV-2 exposure on neurodevelopment of children have produced equivocal results.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is New\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eThis is the first national prospective cohort study on the long-term outcome of children exposed to specific variants of SARS-CoV-2 in utero and, to our knowledge, the first cohort study to clinically assess gross and fine motor development and screen for cognitive as well as social-emotional development in this context.\u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Introduction","content":"\u003cp\u003eSARS-CoV-2 infection during pregnancy has been shown to increase the risk of severe maternal COVID-19, stillbirth, and preterm delivery [1-6]. Subsequent neonatal SARS-CoV-2 infection is rather rare, typically presenting asymptomatically, and mostly acquired during the postnatal period [7-9].\u003c/p\u003e\n\u003cp\u003eAlthough predominantly affecting the pulmonary system, SARS-CoV-2 is a virus with multisystemic symptoms, including neurological manifestations. Neurological symptoms are often nonspecific, such as lethargy or hyperexcitability in infants and headache and myalgia in older children. Other symptoms, such as encephalitis or seizures, occur mainly in severely ill or already neurologically compromised children [10-13].\u003c/p\u003e\n\u003cp\u003eSeveral studies have discussed the potential effects of SARS-CoV-2 on brain development, particularly in cases of intrauterine exposure [14-16]. Potential mechanisms by which the virus could affect infant development are either a direct impact of the virus due to transplacental SARS-CoV-2 transmission, through maternal and secondary fetal immune activation, or in the context of virus-induced pregnancy complications, such as premature births [17, 18].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStudies investigating intrauterine SARS-CoV-2 exposure have produced equivocal results. Several have demonstrated the presence of neurological abnormalities in newborns and infants following in utero exposure to SARS-CoV-2 or postnatal SARS-CoV-2 infection [14, 19-22]. Other studies have not identified a clear association [23-25]. These controversial results could be explained by variability in sample size and study quality. Furthermore, details of the control group have been documented inconsistently [26-28]. Most prospective investigations were based on parental questionnaires and reported concerns about the infant’s neurodevelopment [21, 22, 25, 29]. Standardized clinical assessments have been carried out rarely, and if so, solely on infants [14]. To date, only three studies report on outcomes in older children, using parental self-reporting in 24-month-old children [25, 30, 31].\u003c/p\u003e\n\u003cp\u003ePreviously, no study has distinguished between the intrauterine exposures of different SARS-CoV-2 variants of concern (VOC). In contrast to the wildtype and the Omicron variant, infections with the Alpha and Delta variants have been associated with a higher rate of placentitis and a concomitant increased risk of stillbirth and preterm delivery [32-34], thus possibly impacting fetal and neonatal neurodevelopment to a greater degree than the other variants.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs there is a need for screening for long-term neurodevelopmental deficits of children who were exposed to SARS-CoV-2 prenatally, we have established this multisite national initiative based on the COVID-19 Related Obstetric and Neonatal Outcome Study (CRONOS) [35, 36]. We hypothesize that prenatal exposure to the Alpha and Delta variants increases the risk for neurodevelopmental disorders in terms of changes in motor development, social-emotional development, problem-solving, and communication skills in toddlers and preschoolers. In addition, we assess the same parameters of neurodevelopment in an unexposed control group, thereby also investigating collateral effects of the pandemic on mothers and their offspring.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eStudy aims and objectives\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe present study aims to investigate the neurodevelopmental effects of intrauterine SARS-CoV-2 exposure on children aged 36 to 60 months and to compare the results to an unexposed age-matched control group born in the same time frame.\u003c/p\u003e\n\u003cp\u003ePrimary outcome measures are\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eClinical assessment of motor skills using the Movement Assessment Battery for Children 2\u003csup\u003end\u003c/sup\u003e Edition (M-ABC-2)\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eSecondary outcome measures are\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eScreening for global development in terms of communication, problem-solving, and social-emotional skills using the Ages and Stages Questionnaire 3\u003csup\u003erd\u003c/sup\u003e Edition (ASQ-3)\u003c/li\u003e\n \u003cli\u003eTiming of vaccinations and preventive medical examinations\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eHealthcare system usage in the first year of life\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cem\u003eStudy design and participants\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe study is designed as a prospective population-based cohort study, with participants recruited from the ages of 36 to 60 months at the time of assessment. The identification of exposed children will be conducted through the CRONOS registry. A control group will be recruited through local paediatric practices and targeted outreach via social media platforms (Instagram, LinkedIn, and WhatsApp).\u0026nbsp;Data collection will comprise the administration of questionnaires, including parental self-report measures, in addition to clinical assessments conducted by researchers who are unaware of the children\u0026apos;s exposure status. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist will guide reporting [37].\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSetting\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eCRONOS (COVID-19 Related Obstetric and Neonatal Outcome Study) was a prospective German registry including women with SARS-CoV-2 infection during their pregnancy, with 130 obstetric hospitals actively participating, comprising one-third of all German births [36]. Between April 2020 and February 2023, more than 8500 women and their newborns were included [7]. Maternal SARS-CoV-2 infection was defined as a detection of viral RNA by PCR testing of a nasopharyngeal or oropharyngeal swab, regardless of symptoms or symptom severity, or detection of SARS-CoV-2 antibodies in an antibody-based serum assay in symptomatic women. In the case of PCR testing, some hospitals differentiated between variants of concern (VOC). If this information was not available, the most likely VOC was assigned to the case depending on the time of infection, with the wildtype virus being predominant till February 2021, Alpha from March 2021 to July 2021, Delta from August 2021 to December 2021, and Omicron since January 2022 [38].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition to the CRONOS-Kids principal investigator\u0026apos;s research team, four university hospitals were selected as consortium partners based on their previous recruitment rates in the CRONOS registry and the number of eligible patients.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSampling and recruitment\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eExposure cohort\u003c/p\u003e\n\u003cp\u003eAs the objective of the study is to assess the possible impact of the Alpha and Delta variants on the neurodevelopment of the offspring, families are eligible for study inclusion when the pregnant woman was infected between 01.03.2021 and 31.12.2021, or when infection with Alpha or Delta was confirmed via PCR test, regardless of the timing of infection. Pregnant women are required to have agreed during initial enrolment in CRONOS to be re-contacted. After identifying eligible women by the CRONOS study centre, families are contacted by the local study sites and invited to participate in the CRONOS-Kids study. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUnexposed control group\u003c/p\u003e\n\u003cp\u003eA cohort of children without known or documented intrauterine exposure to SARS-CoV-2 is recruited using probability sampling. Local paediatricians in outpatient practices are invited to provide study information to families during routine preventive medical exams, which are mandatory for four-year-old children in Germany. Additional recruitment efforts include the dissemination of study materials through local kindergartens and nurseries, as well as via personal networks. To enhance public engagement, a dedicated Instagram account featuring a study mascot (@cronos_kids) has been established to share information about the study with a broader audience.\u003c/p\u003e\n\u003cp\u003eA potential SARS-CoV-2 infection in childhood will be recorded in both groups and considered in secondary analyses.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWritten consent is obtained from all participants.\u003c/p\u003e\n\u003cp\u003eRecruitment\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRecruitment started on 1 April 2025 and will continue through December 2025. Families interested in participating are invited to contact the CRONOS-Kids coordinating team via the official study website (http://cronos-kids.de) to schedule an appointment at one of the five study sites. Pseudonymisation is carried out centrally by the coordination team using an eight-digit code. The research team conducting developmental assessments remains blinded to the exposure status of the children, as they do not have access to the pseudonymization key.\u0026nbsp;Parents accompanying the children are informed of the blinding procedure and asked not to disclose any information regarding SARS-CoV-2 infection during pregnancy.\u003c/p\u003e\n\u003cp\u003eWe aim to recruit at least 125 children who were exposed in utero and 125 unexposed children.\u003c/p\u003e\n\u003cp\u003eSample size calculation\u003c/p\u003e\n\u003cp\u003eWe calculated that 64 patients per group are needed, i.e., 128 patients in total, to detect a difference of 0.5 standard deviation in an unpaired t-test in mean M-ABC-2 total scores (Cohen\u0026rsquo;s d = 0.5), with an alpha level of 0.05 and a power of 0.8 [39].\u003c/p\u003e\n\u003cp\u003eExclusion criteria\u003c/p\u003e\n\u003cp\u003eChildren with major congenital anomalies, regardless of intrauterine infection status, are excluded from analysis. Children are eligible for assessment regardless of whether they are preterm or not singletons.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eStudy instruments\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePrimary Outcome\u003c/p\u003e\n\u003cp\u003eThe primary objective of this study is to clinically assess the motor skills of all participating children. For this, the M-ABC-2 will be used [40]. It consists of three movement domains: manual dexterity (MD), aiming and catching (AC), and balance (B), with two (AC) or three (MD and B) different tasks each. There are three age bands available, the first (3 to 6 years) being used in this study. The M-ABC-2 was chosen because of its validation in Western European children, including German children, the availability of a German translation, an appropriate age range, internal reliability (r=.97), and short administration time (20 to 30 minutes). We will use the total score as the primary outcome. The total score ranges from 14 to \u0026ge;108 (total scores above 108 points do not result in further improvement of the percentile rank).\u003c/p\u003e\n\u003cp\u003eRater training was provided prior to the start of the study, based on a previously published rater training programme for the assessment of observations [41] using a four-step approach: 1. Conveying expertise: Expertise in child development was provided by shadowing paediatricians in outpatient care and by accompanying psychologists and physiotherapists in developmental assessments. 2. Self-study: The research team familiarised themselves with the assessment tool and the theoretical aspects of rater error. 3. First assessment with experts: The research team shadowed experts as they performed two clinical assessments using the M-ABC-2 and simultaneously scored the results with the experts. \u0026nbsp;4. Pilot testing: Two clinical assessments and consecutive scoring were conducted by the research team under the supervision of experts. All consecutive tests are performed by the same research team to ensure a high interrater reliability.\u003c/p\u003e\n\u003cp\u003eSecondary Outcome\u003c/p\u003e\n\u003cp\u003eTo screen global development, the age-appropriate questionnaires of the ASQ-3 will be used. Each questionnaire contains five domains: communication, gross motor, fine motor, problem-solving, and personal-social development, with six questions each. Every question can be rated according to the child\u0026rsquo;s abilities with \u0026ldquo;yes\u0026rdquo;, \u0026ldquo;sometimes\u0026rdquo;, and \u0026ldquo;not yet\u0026rdquo;, scored 10, 5, or 0 points, respectively. Each domain is analysed separately with total scores ranging from 0 to 60. Age-specific thresholds are defined and validated, indicating potentially increased risk for neurodevelopmental delay [42].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor screening social-emotional skills, the parent questionnaire for supplementary developmental assessment (EEE - \u0026ldquo;Elternfragebogen zur erg\u0026auml;nzenden Entwicklungsbeurteilung\u0026rdquo;) will be used [43]. The EEE can be used in preventive medical examinations (PMEs) that are mandatory in Germany at different ages of a child [44]. They compile specific sets of social-emotional and practical life skills that are expected to be acquired at that age. Each EEE comprises a different number of questions, ranging from 27 (10 to 12 months) to 35 (60 to 64 months), which can be rated with \u0026ldquo;yes\u0026rdquo; or \u0026ldquo;no\u0026rdquo;.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA web-based general questionnaire was developed on REDCap (Research Electronic Data Capture) [45, 46], comprising sections on current and previous pregnancies, birth, child health, postnatal SARS-CoV-2 infection, the child\u0026acute;s media consumption, the maternal quality of life, socioeconomic status, and social desirability. Questions on pregnancy and birth focus on potential confounders of child development, such as pre-existing maternal illness, smoking, drug use, and preterm birth. Questions on child health include postnatal complications, feeding practices, and health care visits. Socioeconomic status is measured using a multidimensional index score consisting of three metric components: education and occupational qualification, occupational status, and net income [47]. The German version of the EuroQoL quality of life questionnaire (EQ-5D-5L) is used to evaluate the perceived quality of life at the time of the analysis [48]. To assess potential confounding in self-reported outcomes, we included questions on social desirability using the SDS-CM scale, consisting of 23 items [49].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTiming of vaccinations and PMEs will be extracted from official vaccination certificates and specific PME documents (so-called \u0026ldquo;U-Heft\u0026rdquo;) and entered into a designated web-based database.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eData collection\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eData will be solely collected by the Marburg University research team on all study sites, thus ensuring a high internal consistency.\u003c/p\u003e\n\u003cp\u003eASQ-3 and EEE questionnaires are sent to parents at least one week before their clinical appointments, thus allowing time for self-assessing their children.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAt the time of clinical assessment, M-ABC-2 will be performed by the research team, blinded to the exposure status of the children. ASQ-3 and EEE questionnaires are collected and checked for completeness. The general questionnaire will be completed during the clinical assessment using a dedicated CRONOS-Kids study tablet (Microsoft Surface 2.0). Data on vaccination and PMEs are also collected on this study tablet.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eBias\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA potential sampling bias is anticipated, as families with higher educational levels and German language proficiency may be more likely to participate in the study. However, since this tendency is expected in both the exposed and unexposed groups, and detailed information on socioeconomic status is being collected, potential confounding will be addressed through statistical adjustment.\u003c/p\u003e\n\u003cp\u003eTo minimize performance and observer bias, the research team conducting the assessments is separate from the coordination team responsible for recruitment and appointment logistics. Furthermore, accompanying parents are instructed not to reveal any information regarding SARS-CoV-2 infection during pregnancy to ensure assessor blinding.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eEthics approval, funding, and registration\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the ethics committee of Marburg University (AZ 114/22), as well as the ethics committees at the local study sites. Research will be conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003eFunding was provided by the German Society for Perinatal Medicine (DGPM, https://www.dgpm-online.org/).\u003c/p\u003e\n\u003cp\u003eThe study was registered at clinicaltrials.gov in April 2025 (NCT06968897).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eStatistical analysis\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe Marburg University research team will be responsible for data acquisition and validation, and conducting the statistical analysis.\u003c/p\u003e\n\u003cp\u003eThe cohort\u0026rsquo;s baseline sociodemographic and clinical characteristics will be compared between the exposure and unexposed control cohorts using appropriate tests depending on variable categories: chi-square tests will be used for categorical variables, and t-tests for continuous variables. There will be no adjustments for study sites.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLogistic regression models will be employed to examine the exposure status and total scores in M-ABC-2, ASQ-3, and the EEE. Adjusting for potential confounders is planned for maternal age, social status, parental education, children\u0026apos;s sex, and gestational age of delivery. Further analysis on ASQ-3 and EEE-scores will include social desirability measured by the SDS-CM scale as a potential confounder. An exploratory subgroup analysis will be performed for the trimester of infection, infection severity, maternal quality of life, and duration of breastfeeding. The timing of vaccinations and PMEs will be analysed descriptively, as well as the healthcare system usage in the first year of life.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe will summarise the amount of missing data in each of the variables for both cohorts separately. Cohorts will be compared using complete cases for the specific outcome parameter. Based on the proposed data collection, we expect the proportion of missing data to be small. In case of a high amount of missing data, we may consider multiple imputation as a sensitivity analysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eP values \u0026lt;.05 will be considered statistically significant. For all analyses, the statistical software SPSS (IBM Corp., Armonk, NY, USA) will be used.\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eTo our knowledge, this is the first prospective cohort study to clinically assess neurodevelopment in 3 to 5-year-old children after intrauterine exposure to the Alpha or Delta variant of SARS-CoV-2. We will conduct a multicentre cohort study based on the CRONOS registry using a carefully designed set of study instruments developed within the CRONOS-Kids study group, incorporating two internationally recognized and validated tools. Furthermore, the exposed children will be compared to a control group of unexposed children of the same age, controlling for potential confounding parameters.\u003c/p\u003e\u003cp\u003eClinical standardized assessments have been rarely used in previous studies investigating the effects of intrauterine exposure to SARS-CoV-2 on children, especially not in children older than 12 months [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. These will be conducted by specifically trained researchers in this study to minimize the possibility of confounding bias. Furthermore, we will systematically examine social desirability, a potential confounding factor in parental assessments of children's development.\u003c/p\u003e\u003cp\u003eWe will exclude children who were exposed to the wildtype or Omicron variant in utero. Previous research on intrauterine exposure to SARS-CoV-2 has yielded inconsistent findings, potentially due to the failure to distinguish between different viral variants. Given that the Alpha and Delta variants have been associated with an elevated risk of stillbirth, preterm birth, placentitis, and neonatal SARS-CoV-2 infection [\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], their impact on fetal neurodevelopment may be more pronounced than that of the wildtype or Omicron variant. Moreover, since neurodevelopmental delay is generally uncommon, aggregating data from multiple virus variants may obscure potential differences in their effects.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe findings of this study will contribute to a more comprehensive understanding of the long-term postnatal effects of SARS-CoV-2 infection during pregnancy, as well as the broader consequences of the pandemic, including social isolation or reduced access to healthcare. A better understanding of these factors could improve care for children exposed to the virus in utero. Insights gained from the long-term effects of SARS-CoV-2 infection and pandemic disruptions could help to prepare for future crises, ensuring better maternal and child health.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eConsent to participate\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eParticipating parents will provide written consent.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConsent to Publish\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eZambrano, L.D., et al., \u003cem\u003eUpdate: Characteristics of Symptomatic Women of Reproductive Age with Laboratory-Confirmed SARS-CoV-2 Infection by Pregnancy Status - United States, January 22-October 3, 2020.\u003c/em\u003e MMWR Morb Mortal Wkly Rep, 2020. \u003cstrong\u003e69\u003c/strong\u003e(44): p. 1641-1647.\u003c/li\u003e\n \u003cli\u003eSitter, M., et al., \u003cem\u003ePregnant and Postpartum Women Requiring Intensive Care Treatment for COVID-19-First Data from the CRONOS-Registry.\u003c/em\u003e J Clin Med, 2022. \u003cstrong\u003e11\u003c/strong\u003e(3).\u003c/li\u003e\n \u003cli\u003eBoettcher, L.B. and T.D. Metz, \u003cem\u003eMaternal and neonatal outcomes following SARS-CoV-2 infection.\u003c/em\u003e Semin Fetal Neonatal Med, 2023. \u003cstrong\u003e28\u003c/strong\u003e(1): p. 101428.\u003c/li\u003e\n \u003cli\u003eAllotey, J., et al., \u003cem\u003eClinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and meta-analysis.\u003c/em\u003e Bmj, 2020. \u003cstrong\u003e370\u003c/strong\u003e: p. m3320.\u003c/li\u003e\n \u003cli\u003eIannaccone, A., et al., \u003cem\u003eIs the risk of still and preterm birth affected by the timing of symptomatic SARS-CoV-2 infection during pregnancy? Data from the COVID-19 Related Obstetrics and Neonatal Outcome Study Network, Germany.\u003c/em\u003e Am J Obstet Gynecol, 2023. \u003cstrong\u003e228\u003c/strong\u003e(3): p. 351-352.e2.\u003c/li\u003e\n \u003cli\u003eWei, S.Q., et al., \u003cem\u003eThe impact of COVID-19 on pregnancy outcomes: a systematic review and meta-analysis.\u003c/em\u003e Cmaj, 2021. \u003cstrong\u003e193\u003c/strong\u003e(16): p. E540-e548.\u003c/li\u003e\n \u003cli\u003eMand, N., et al., \u003cem\u003eVertical transmission of SARS-CoV-2 - data from the German COVID-19 related obstetric and neonatal outcome study (CRONOS).\u003c/em\u003e J Perinat Med, 2024.\u003c/li\u003e\n \u003cli\u003eAl-Lawama, M., et al., \u003cem\u003ePerinatal Transmission and Clinical Outcomes of Neonates Born to SARS-CoV-2-Positive Mothers.\u003c/em\u003e J Clin Med Res, 2021. \u003cstrong\u003e13\u003c/strong\u003e(8): p. 420-424.\u003c/li\u003e\n \u003cli\u003eDe Luca, D., et al., \u003cem\u003eTransmission of SARS-CoV-2 from mother to fetus or neonate: What to know and what to do?\u003c/em\u003e Semin Fetal Neonatal Med, 2023. \u003cstrong\u003e28\u003c/strong\u003e(1): p. 101429.\u003c/li\u003e\n \u003cli\u003eStafstrom, C.E., \u003cem\u003eNeurological effects of COVID-19 in infants and children.\u003c/em\u003e Dev Med Child Neurol, 2022. \u003cstrong\u003e64\u003c/strong\u003e(7): p. 818-829.\u003c/li\u003e\n \u003cli\u003eDoenhardt, M., et al., \u003cem\u003eEpidemiology of 7375 children and adolescents hospitalized with COVID-19 in Germany, reported via a prospective, nationwide surveillance study in 2020-2022.\u003c/em\u003e Sci Rep, 2024. \u003cstrong\u003e14\u003c/strong\u003e(1): p. 47.\u003c/li\u003e\n \u003cli\u003eLaRovere, K.L., et al., \u003cem\u003eNeurologic Involvement in Children and Adolescents Hospitalized in the United States for COVID-19 or Multisystem Inflammatory Syndrome.\u003c/em\u003e JAMA Neurol, 2021. \u003cstrong\u003e78\u003c/strong\u003e(5): p. 536-547.\u003c/li\u003e\n \u003cli\u003eRaschetti, R., et al., \u003cem\u003eSynthesis and systematic review of reported neonatal SARS-CoV-2 infections.\u003c/em\u003e Nat Commun, 2020. \u003cstrong\u003e11\u003c/strong\u003e(1): p. 5164.\u003c/li\u003e\n \u003cli\u003eAldrete-Cortez, V., et al., \u003cem\u003eInfants prenatally exposed to SARS-CoV-2 show the absence of fidgety movements and are at higher risk for neurological disorders: A comparative study.\u003c/em\u003e PLoS One, 2022. \u003cstrong\u003e17\u003c/strong\u003e(5): p. e0267575.\u003c/li\u003e\n \u003cli\u003eJoma, M., et al., \u003cem\u003eCOVID-19 and Pregnancy: Vertical Transmission and Inflammation Impact on Newborns.\u003c/em\u003e Vaccines (Basel), 2021. \u003cstrong\u003e9\u003c/strong\u003e(4).\u003c/li\u003e\n \u003cli\u003eShook, L.L., et al., \u003cem\u003eCOVID-19 in pregnancy: implications for fetal brain development.\u003c/em\u003e Trends Mol Med, 2022. \u003cstrong\u003e28\u003c/strong\u003e(4): p. 319-330.\u003c/li\u003e\n \u003cli\u003eBrum, A.C. and N.E. Vain, \u003cem\u003eImpact of perinatal COVID on fetal and neonatal brain and neurodevelopmental outcomes.\u003c/em\u003e Semin Fetal Neonatal Med, 2023. \u003cstrong\u003e28\u003c/strong\u003e(2): p. 101427.\u003c/li\u003e\n \u003cli\u003eDubey, H., et al., \u003cem\u003eSARS-CoV-2 (COVID-19) as a possible risk factor for neurodevelopmental disorders.\u003c/em\u003e Front Neurosci, 2022. \u003cstrong\u003e16\u003c/strong\u003e: p. 1021721.\u003c/li\u003e\n \u003cli\u003eAyed, M., et al., \u003cem\u003eNeurodevelopmental outcomes of infants born to mothers with SARS-CoV-2 infections during pregnancy: a national prospective study in Kuwait.\u003c/em\u003e BMC Pediatr, 2022. \u003cstrong\u003e22\u003c/strong\u003e(1): p. 319.\u003c/li\u003e\n \u003cli\u003eEdlow, A.G., et al., \u003cem\u003eNeurodevelopmental Outcomes at 1 Year in Infants of Mothers Who Tested Positive for SARS-CoV-2 During Pregnancy.\u003c/em\u003e JAMA Netw Open, 2022. \u003cstrong\u003e5\u003c/strong\u003e(6): p. e2215787.\u003c/li\u003e\n \u003cli\u003eHill, R.A., et al., \u003cem\u003eInvestigating the impact of severe maternal SARS-CoV-2 infection on infant DNA methylation and neurodevelopment.\u003c/em\u003e Mol Psychiatry, 2025. \u003cstrong\u003e30\u003c/strong\u003e(5): p. 1976-1984.\u003c/li\u003e\n \u003cli\u003eWang, Y., et al., \u003cem\u003eImpact of Covid-19 in pregnancy on mother\u0026apos;s psychological status and infant\u0026apos;s neurobehavioral development: a longitudinal cohort study in China.\u003c/em\u003e BMC Med, 2020. \u003cstrong\u003e18\u003c/strong\u003e(1): p. 347.\u003c/li\u003e\n \u003cli\u003eShuffrey, L.C., et al., \u003cem\u003eAssociation of Birth During the COVID-19 Pandemic With Neurodevelopmental Status at 6 Months in Infants With and Without In Utero Exposure to Maternal SARS-CoV-2 Infection.\u003c/em\u003e JAMA Pediatr, 2022. \u003cstrong\u003e176\u003c/strong\u003e(6): p. e215563.\u003c/li\u003e\n \u003cli\u003eFirestein, M.R., et al., \u003cem\u003eAssessment of Neurodevelopment in Infants With and Without Exposure to Asymptomatic or Mild Maternal SARS-CoV-2 Infection During Pregnancy.\u003c/em\u003e JAMA Netw Open, 2023. \u003cstrong\u003e6\u003c/strong\u003e(4): p. e237396.\u003c/li\u003e\n \u003cli\u003eJaswa, E.G., et al., \u003cem\u003eIn Utero Exposure to Maternal COVID-19 and Offspring Neurodevelopment Through Age 24 Months.\u003c/em\u003e JAMA Netw Open, 2024. \u003cstrong\u003e7\u003c/strong\u003e(10): p. e2439792.\u003c/li\u003e\n \u003cli\u003eHessami, K., et al., \u003cem\u003eCOVID-19 Pandemic and Infant Neurodevelopmental Impairment: A Systematic Review and Meta-analysis.\u003c/em\u003e JAMA Netw Open, 2022. \u003cstrong\u003e5\u003c/strong\u003e(10): p. e2238941.\u003c/li\u003e\n \u003cli\u003ePinheiro, G., et al., \u003cem\u003eEffects of intrauterine exposure to SARS-CoV-2 on infants\u0026apos; development: a rapid review and meta-analysis.\u003c/em\u003e Eur J Pediatr, 2023. \u003cstrong\u003e182\u003c/strong\u003e(5): p. 2041-2055.\u003c/li\u003e\n \u003cli\u003eJackson, R., et al., \u003cem\u003eAntenatal and neonatal exposure to SARS-CoV-2 and children\u0026apos;s development: a systematic review and meta-analysis.\u003c/em\u003e Pediatr Res, 2024. \u003cstrong\u003e96\u003c/strong\u003e(1): p. 40-50.\u003c/li\u003e\n \u003cli\u003eHardie, I., et al., \u003cem\u003eEarly childhood developmental concerns following SARS-CoV-2 infection and COVID-19 vaccination during pregnancy: a Scottish population-level retrospective cohort study.\u003c/em\u003e Lancet Child Adolesc Health, 2025. \u003cstrong\u003e9\u003c/strong\u003e(3): p. 162-171.\u003c/li\u003e\n \u003cli\u003eJackson, R., et al., \u003cem\u003eAssociation of antenatal or neonatal SARS-COV-2 exposure with developmental and respiratory outcomes, and healthcare usage in early childhood: a national prospective cohort study.\u003c/em\u003e EClinicalMedicine, 2024. \u003cstrong\u003e72\u003c/strong\u003e: p. 102628.\u003c/li\u003e\n \u003cli\u003eVrantsidis, D.M., et al., \u003cem\u003eNeurodevelopment in the First 2 Years of Life Following Prenatal Exposure to Maternal SARS-CoV-2 Infection.\u003c/em\u003e JAMA Netw Open, 2024. \u003cstrong\u003e7\u003c/strong\u003e(11): p. e2443697.\u003c/li\u003e\n \u003cli\u003eFitzgerald, B., et al., \u003cem\u003eFetal Deaths in Ireland Due to SARS-CoV-2 Placentitis Caused by SARS-CoV-2 Alpha.\u003c/em\u003e Arch Pathol Lab Med, 2022. \u003cstrong\u003e146\u003c/strong\u003e(5): p. 529-537.\u003c/li\u003e\n \u003cli\u003eMerriel, A., B. Fitzgerald, and K. O\u0026apos;Donoghue, \u003cem\u003eSARS-CoV-2-Placental effects and association with stillbirth.\u003c/em\u003e Bjog, 2024. \u003cstrong\u003e131\u003c/strong\u003e(4): p. 385-400.\u003c/li\u003e\n \u003cli\u003eStenton, S., et al., \u003cem\u003eSARS-COV2 placentitis and pregnancy outcome: A multicentre experience during the Alpha and early Delta waves of coronavirus pandemic in England.\u003c/em\u003e EClinicalMedicine, 2022. \u003cstrong\u003e47\u003c/strong\u003e: p. 101389.\u003c/li\u003e\n \u003cli\u003ePecks, U., et al., \u003cem\u003ePregnancy and SARS-CoV-2 Infection in Germany-the CRONOS Registry.\u003c/em\u003e Dtsch Arztebl Int, 2020. \u003cstrong\u003e117\u003c/strong\u003e(49): p. 841-842.\u003c/li\u003e\n \u003cli\u003ePecks, U., et al., \u003cem\u003eSARS-CoV-2 Infection During Pregnancy.\u003c/em\u003e Dtsch Arztebl Int, 2022. \u003cstrong\u003e119\u003c/strong\u003e(35-36): p. 588-594.\u003c/li\u003e\n \u003cli\u003evon Elm, E., et al., \u003cem\u003eThe Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies.\u003c/em\u003e J Clin Epidemiol, 2008. \u003cstrong\u003e61\u003c/strong\u003e(4): p. 344-9.\u003c/li\u003e\n \u003cli\u003eSchillung J, B.S., Tolksdorf K, \u003cem\u003eZweite Aktualisierung der \u0026bdquo;Retrospektiven Phaseneinteilung der COVID-19-Pandemie in Deutschland\u0026ldquo;.\u003c/em\u003e Epid Bull, 2022. \u003cstrong\u003e10\u003c/strong\u003e: p. 3-5.\u003c/li\u003e\n \u003cli\u003eFaul, F., et al., \u003cem\u003eG*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences.\u003c/em\u003e Behav Res Methods, 2007. \u003cstrong\u003e39\u003c/strong\u003e(2): p. 175-91.\u003c/li\u003e\n \u003cli\u003ePetermann, F., B\u0026ouml;s, K., \u0026amp; Kastner, J, \u003cem\u003eMovement Assessment Battery for Children - Second Edition. Deutsche Bearbeitung\u003c/em\u003e. 4., \u0026uuml;berarbeitete und erweiterte Auflage ed. 2015: Pearson.\u003c/li\u003e\n \u003cli\u003eMand, N., et al., \u003cem\u003eSuccessful implementation of a rater training program for medical students to evaluate simulated pediatric emergencies.\u003c/em\u003e GMS J Med Educ, 2023. \u003cstrong\u003e40\u003c/strong\u003e(4): p. Doc47.\u003c/li\u003e\n \u003cli\u003eSquires, J., \u0026amp; Bricker, D., \u003cem\u003eAges \u0026amp; Stages Questionnaires\u0026reg;, Third Edition (ASQ-3\u0026trade;): A Parent-Completed Child Monitoring System.\u003c/em\u003e 2009, Baltimore Paul H. Brookes Publishing Co., Inc.\u003c/li\u003e\n \u003cli\u003ePetermann, F. and T. Macha, \u003cem\u003eElternfrageb\u0026ouml;gen zur erg\u0026auml;nzenden Entwicklungsbeurteilung bei den kinder\u0026auml;rztlichen Vorsorgeuntersuchungen U6 bis U9: EEE U6-U9\u003c/em\u003e. 2003: Swets Test Services.\u003c/li\u003e\n \u003cli\u003eSchmidtke C, K.B., Starker A, Lampert T (Robert Koch-Institut), \u003cem\u003eInanspruchnahme der Fr\u0026uuml;herkennungsuntersuchungen f\u0026uuml;r Kinder in Deutschland \u0026ndash; Querschnittergebnisse aus KiGGS Welle 2.\u003c/em\u003e Journal of Health Monitoring, 2018. \u003cstrong\u003e3\u003c/strong\u003e(3).\u003c/li\u003e\n \u003cli\u003eHarris, P.A., et al., \u003cem\u003eResearch electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support.\u003c/em\u003e J Biomed Inform, 2009. \u003cstrong\u003e42\u003c/strong\u003e(2): p. 377-81.\u003c/li\u003e\n \u003cli\u003eHarris, P.A., et al., \u003cem\u003eThe REDCap consortium: Building an international community of software platform partners.\u003c/em\u003e J Biomed Inform, 2019. \u003cstrong\u003e95\u003c/strong\u003e: p. 103208.\u003c/li\u003e\n \u003cli\u003eLampert, T., et al., \u003cem\u003eMessung des sozio\u0026ouml;konomischen Status in der KiGGS-Studie.\u003c/em\u003e Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz, 2014. \u003cstrong\u003e57\u003c/strong\u003e(7): p. 762-770.\u003c/li\u003e\n \u003cli\u003eHerdman, M., et al., \u003cem\u003eDevelopment and preliminary testing of the new five-level version of EQ-5D (EQ-5D-5L).\u003c/em\u003e Qual Life Res, 2011. \u003cstrong\u003e20\u003c/strong\u003e(10): p. 1727-36.\u003c/li\u003e\n \u003cli\u003eL\u0026uuml;ck, H., Timaeus E., \u003cem\u003eSoziale Erw\u0026uuml;nschtheit (SDS-CM)\u003c/em\u003e. 2014: Zusammenstellung sozialwissenschaftlicher Items und Skalen (ZIS).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Marburg University, Faculty of Medicine, Neonatology and Pediatric Intensive Care, Department of Paediatrics, Marburg, Germany","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":"SARS-CoV-2, pregnancy, child, development","lastPublishedDoi":"10.21203/rs.3.rs-8295431/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8295431/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInfection with SARS-CoV-2 during pregnancy increases the risk for adverse events in mothers and their newborns. Research is increasingly exploring the potential consequences of intrauterine exposure to the developing nervous system. However, there is still a lack of high-quality studies on long-term outcomes. The CRONOS-Kids study aims to investigate the global development of children after exposure to SARS-CoV-2 in utero in comparison to an unexposed control group. This paper outlines the CRONOS-Kids study protocol.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study is designed as a prospective population-based cohort study, and will recruit children aged 36–60 months at the time of assessment. The exposed cohort will be recruited from the German CRONOS registry and will only include participants who have been exposed to the Alpha and Delta variants of SARS-CoV-2. The unexposed cohort will be recruited by local paediatricians and via social media. For clinical evaluations, the Movement Assessment Battery for Children 2nd Edition will be used. Parental self-reports on development will use the Ages and Stages Questionnaire 3rd Edition. Additional questionnaires cover general information about maternal and child health, vaccinations, healthcare usage, media consumption, maternal quality of life, and social status.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUntil December 2025, we aim to recruit 125 exposed and 125 unexposed children across five study sites.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe CRONOS-Kids study will explore the impact of intrauterine SARS-CoV-2 exposure of specific virus variants on long-term neurologic outcomes in children, as well as the broader consequences of the pandemic.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was registered at clinicaltrials.gov in April 2025 (NCT06968897).\u003c/p\u003e","manuscriptTitle":"From CRONOS to CRONOS-Kids: Investigating Neurological Development in Toddlers After Maternal SARS-CoV-2 Infection During Pregnancy – A Study Protocol For A Prospective Cohort Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-09 05:31:31","doi":"10.21203/rs.3.rs-8295431/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":"96c35239-10d1-44d5-b035-18b22d683e4e","owner":[],"postedDate":"December 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-09T05:31:31+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-09 05:31:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8295431","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8295431","identity":"rs-8295431","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}