Spontaneous partial chorioamniotic membrane separation followed by the formation of amniotic bands:a case report

Spontaneous partial chorioamniotic membrane separation followed by the formation of amniotic bands:a case report | 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 Case Report Spontaneous partial chorioamniotic membrane separation followed by the formation of amniotic bands:a case report Shouheng Wu, Xi Tan, Rong Zhou This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6700418/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Oct, 2025 Read the published version in BMC Pregnancy and Childbirth → Version 1 posted 17 You are reading this latest preprint version Abstract Background Chorioamniotic membrane separation (CMS) is associated with various adverse pregnancy outcomes, including miscarriage, preterm labor, stillbirth, amniotic band syndrome, etc. Spontaneous CMS is extremely rare. At present, there is no standardized monitoring and treatment protocols for CMS. Case Presentation We present an unusual case of spontaneous partial CMS with amniotic band diagnosed through ultrasonography at 27 +6 weeks of gestation in a 34-year-old woman. About one month later, an emergency cesarean section was performed because of unavoidable preterm labor and fetal transverse presentation, resulting in the successful delivery of a healthy baby. The partial CMS with amniotic band was confirmed by the examination for the placenta. The infant underwent a 10-month follow-up period and currently is in good health despite experiencing two respiratory infections. Conclusions Based on our experience and combined with previous research, we think that etiological screening is the primary priority for CMS cases. Expectant management under close ultrasonographic scans and prolonging gestational age as much as possible may be beneficial for neonatal prognosis. Chorioamniotic membrane separation Amniotic band Etiology Pregnancy outcomes Treatment Figures Figure 1 Figure 2 Background As we know, the fetal membranes consist of two distinct layers: the inner amniotic membrane and the outer chorionic villi, originating from different embryonic layers. These layers undergo separation before the 14th week of gestation, followed by fusion of the chorioamniotic membrane between the 14th and 16th weeks of gestation. Any separation occurring after the 16th week is considered abnormal and is known as chorioamniotic membrane separation (CMS) [ 1 ]. Prenatal ultrasonographic findings of CMS are classified as either partial or complete, with an incidence of 0.023 to 0.534% [ 2 ]. Intraamniotic surgery and fetal chromosomal aneuploidy are established etiologies of CMS [ 1 , 2 ]. However, spontaneous CMS is extremely rare. Herein, we report a case of spontaneous partial CMS followed by the formation of amniotic bands, and no case has been reported before. Case Presentation A 34-year-old woman with a history of four pregnancies, with one live birth through vaginal delivery seven years ago and two abortions, conceived her current pregnancy naturally. Fetal nuchal translucency measurement was within normal ranges. Non-invasive prenatal testing indicated low risk, and amniocentesis was not performed during this pregnancy. At 23 weeks of gestation, an ultrasound examination at a local hospital revealed a partial detachment of the chorioamniotic membrane for the first time, with the fetus positioned above the membrane in the amniotic cavity. Subsequent ultrasound at 27 + 6 weeks of gestation indicated the presence of banded echoes in the central part of the amniotic cavity, which divided the uterine cavity into upper and lower portions. The fetus was confined to the upper part of the amniotic cavity. Unfortunately, ultrasound images from local hospitals are not available. At 31 weeks of gestation, the patient experienced irregular contractions and a slight vaginal fluid discharge. The patient was referred to West China Second Hospital, a maternal and child care center in west China. The ultrasound examination (Fig. 1 a,b,c) revealed that the fetus was positioned transversely and that the chorioamniotic membrane had partially detached, the uterine cavity contained 2−3 banded strong echoes. Some of these echoes were in close proximity to the fetus, which was surrounded by reduced amniotic fluid. The fetus was predominantly situated above the banded strong echoes, while the amniotic fluid was primarily located below them. Furthermore, the umbilical cord was positioned within the pool of amniotic fluid beneath the banded strong echoes. Treatment included the administration of magnesium sulfate to protect fetal cerebral nerves, dexamethasone to facilitate fetal lung maturation, and ritodrine hydrochloride to inhibit contractions. At 31 + 5 weeks of gestation, the patient experienced unavoidable preterm labor. An emergency cesarean section was performed because of a transverse presentation. The neonate, a male weighing 1,810 g, exhibited no apparent malformations. Apgar scores at 1, 5, and 10 min were 6, 8, and 9, respectively. Subsequently, the neonate was intubated and transferred to the neonatal intensive care unit (NICU). Placental examination (Fig. 2 ) indicated a partial chorionic amniotic separation with amniotic band formation. The infant received systemic treatment for 40 days in the NICU for respiratory distress syndrome before being discharged. The mother was discharged without complications one week postoperatively. Over a 10-month follow-up period, the infant was hospitalized twice for severe pneumonia. No chromosomal abnormalities, genetic disorders, or inherited metabolic disorders were identified in the infant through relevant examinations. The infant's growth and development progressed normally. Discussion and conclusions The occurrence of CMS, particularly in spontaneous cases, is relatively rare. Currently, no standardized approach for managing CMS is available. Although no established grading system exists for CMS, Romain et al. proposed a classification based on the extent of separation [ 3 ]. The classification was as follows: "mild" for amniotic membrane detachment of 50%. However, the clinical utility of this criterion for determining pregnancy outcome and fetal prognosis remains unclear. The primary cause of CMS is a medical complication resulting from invasive fetal procedures, including amniocentesis, pleurodesis, fetoscopy, or fetal surgery, which disrupt the fusion of the two membranes [ 4 ]. A study indicated that the occurrence of CMS following fetoscopy is approximately 40% [ 5 ]. The secondary cause is fetal chromosomal aneuploidy (trisomy 21, 13, and 18) or fetal connective tissue disorders (restrictive dermopathy), resulting in membrane insufficiency and incomplete chorioamniotic fusion [ 1 ]. Bromley et al. performed prenatal diagnosis through amniocentesis in ten patients with CMS and reported that three fetuses had Down syndrome [ 6 ]. Another study in 2017 identified distinct miRNA expression patterns in fetal membranes specific to tissues and regions. The miRNA expression, including miR-99a, miR-125b, and let-7c, was found to be downregulated in the fetal membranes of patients with trisomy 21. This downregulation potentially contributed to fetal membrane abnormalities associated with trisomy 21, including delayed separation of chorionic villi from the amniotic membrane or delayed fusion between chorionic villi and amniotic membrane [ 7 ]. Furthermore, a few cases have been associated with seromucinous collection resulting from chorionic villous hemangioma [ 8 ]. Joung et al. reported a case where post-cesarean section uterine scarring was proposed as a potential factor in spontaneous CMS [ 9 ]. Jolien suggested that endothelial rupture in preterm premature rupture of membranes (PPROM), resulting in amniotic fluid accumulation in the space between the chorionic and amniotic membranes, could be an etiology of CMS [ 1 ]. However, spontaneous CMS cases without a history of invasive procedures or fetal chromosomal abnormalities are significantly rare, and the precise mechanism remains unclear. In our case, the etiology of CMS was uncertain. We excluded a history of invasive fetal surgery, fetal chromosomal abnormalities, and other uncommon causes. CMS was initially identified through ultrasound at 23 weeks of gestation at an external facility. Before the fetus is transferred to our hospital in the uterus, the amniotic membrane, previously separated, ruptured, forming amniotic band. This event did not physically injure the fetus and umbilical cord. However, the fetus was confined in an restricted environment with insufficient amniotic fluid for nearly one month. This resulted in some impairment of fetal development, particularly lung maturation, as demonstrated by respiratory distress syndrome in the newborn post-delivery and multiple lung infections during infancy. Previous studies indicate that CMS is associated with various adverse pregnancy outcomes, including miscarriage, preterm labor, fetal growth restriction, in utero fetal death, neonatal death, amniotic band syndrome, and umbilical cord complications [ 2 , 6 ]. Fetal malformations can result from amniotic band syndrome and/or reduced amniotic fluid levels. Previously, a study revealed a significantly higher stillbirth rate in cases of CMS occurring before 24 weeks of gestation [ 10 ]. A study involving 118 instances of CMS reported that 53.1% (60/113) of deliveries resulted in preterm births, and 6.2% (7/113) in intrauterine fetal deaths. Furthermore, among 104 postpartum follow-up cases, neonatal deaths occurred in 5.8% (6/104) and infant deaths in 0.96% (1/104). The overall perinatal mortality rate (including intrauterine fetal deaths and neonatal deaths) was 11.0% (13/118) [ 11 ]. Chorionic villus separation has been associated with an increased risk of PPROM and preterm labor [ 10 , 11 ]. This is due to the normal attachment of the chorionic villus with the maternal meconium, which provides support to the amniotic membrane against physical pressures. This supportive function is lost when separation occurs, which can result in PPROM. Apart from physical factors, membrane separation can trigger preterm labor and premature rupture of membranes by releasing chemical mediators. In this case, we propose that following amniochorionic separation, the amniotic cavity ruptured, resulting in the formation of amniotic band that secured the fetus to the upper uterine region. Consequently, the amniotic fluid surrounding the fetus decreased. Remarkably, the fetus did not experience malformations, fetal distress, or umbilical cord complications, which is a very rare case. However, PPROM and preterm labor were unavoidable during hospitalization for observation. There is a lack of standardized monitoring and treatment protocols for CMS. It is recommended that, in cases of spontaneous CMS without a history of invasive fetal surgery, chromosomal analysis should be performed to exclude fetal aneuploidy. If there are no fetal chromosomal or structural abnormalities, the pregnancy can be continued with a favorable neonatal prognosis anticipated. Vigilant monitoring throughout the pregnancy is essential, including regular ultrasound assessments to monitor fetal growth, amniotic fluid levels, the presence of amniotic bands, and the potential for umbilical cord compression to evaluate fetal condition. Hospitalization for monitoring and treatment can reduce fetal mortality [ 2 , 12 ]. Invasive surgical intervention may be beneficial in improving neonatal outcomes by addressing the constriction caused by amniotic band formation. Schlehe documented a case in which a patient with CMS underwent fetoscopic release of amniotic bands at 24 weeks of gestation, resulting in the extension of gestation to 34 weeks [ 13 ]. Although our case did not involve serious complications of amniotic band syndrome, it is important to investigate the feasibility of performing amniotic band release prior to premature rupture of membranes to reduce the impact of amniotic band constriction and decreased amniotic fluid volume on fetal development. Abbreviations CMS Chorioamniotic membrane separation NICU neonatal intensive care unit PPROM preterm premature rupture of membranes Declarations Ethics approval and consent to participate This is a case study, so no ethical approval was required. The informed consent of the patient involved in the article has been obtained. Consent for publication The patient provided written informed consent for publication of this case report. Moreover, the manuscript does not involve any personal information. Data Availability All data generated or analyzed during this study are included in this published article. The datasets used and/or analyzed during this study are available from the corresponding author on request. Competing interests The authors declare no competing interests. Funding None. Authors ’ contributions Shouheng Wu and Rong Zhou contributed to the study conception and design. Xi Tan carried out the data collection. Shouheng Wu drafted the manuscript. Rong Zhou reviewed and edited the manuscript. All authors read and approved the final manuscript. Acknowledgements Not applicable. References Govaerts J, Cryns P, Jacquemyn Y. Spontaneous chorioamniotic membrane separation discovered by preterm prelabor rupture of membranes. Clin Case Rep. 2019 ;7(4):762–5. Sydorak RM, Hirose S, Sandberg PL, Filly RA, Harrison MR, Farmer DL, et al. Chorioamniotic membrane separation following fetal surgery. J Perinatol.2002;22:407-10. Corroenne R, Yepez M, Barth J, Pan E, Whitehead WE, Espinoza J,et al. Chorioamniotic membrane separation following fetal myelomeningocele repair: incidence, risks factors and impact on perinatal outcome. Ultrasound Obstet Gynecol.2020;56(5):684-93. Levine D, Callen PW, Pender SG, McArdle CR, Messina L, Shekhar A, et al. Chorioamniotic separation after second trimester genetic amniocentesis: importance and frequency. Radiology. 1998;209:175-81. Pedreira DAL, Zanon N, Nishikuni K, Moreira de Sá RA, Acacio GL, Chmait RH, et al. Endoscopic surgery for the antenatal treatment of myelomeningocele: the CECAM trial. Am J Obstet Gynecol. 2016;214(1):111.e1-e11. Bromley B, Shipp TD, Benacerraf BR. Amnion-chorion separation after 17 weeks’ gestation. Obstet Gynecol.1999;94(6):1024-6. Modi BP, Washington S, Walsh SW, Jackson-Cook C, Archer KJ, Strauss JF 3rd.Expression patterns of the chromosome 21 MicroRNA cluster (miR- 99a, miR-125b and let-7c) in chorioamniotic membranes. Placenta,2017;49:1-9. Eom HM, Kim YN, Choi BH, Jeong EJ, Byun JM, Jeong DH, et al. Chorioamniotic membrane separation caused by the seromucinous collection from a placental chorioangioma. Obstet Gynecol Sci. 2016;59(3):233-7. Joung EJ, You SK, Lee JY, Ahn JW, Yun NR, Hwang SO. A live birth after spontaneous complete chorioamniotic membrane separation associated with uterine scar. Obstet Gynecol Sci.2016;59(2):144-7. Bibbo C, Little SE, Bsat J, Botka KA, Benson CB, Robinson JN.Chorioamniotic Separation Found on Obstetric Ultrasound and Perinatal Outcome. AJP Rep.2016;6(3): e337-43. Zhu KH, Young BC, Shamshirsaz AA, Espinoza J, Sanz-Cortes M, Donepudi R, et al. Outcomes of prenatally diagnosed spontaneous chorioamniotic membrane separation in singleton pregnancies: A systematic review of case series and case reports. Prenatal Diagnosis. 2020;40(11):1366–74. Ishikawa G, Satomi M, Inagawa-Ichikawa T, Abe T, Akira S, Takeshita T. A case report of complete chorioamniotic membrane separation. J Nippon Med Sch.2011;78(2):120-5. Schlehe B, Elsässer M, Bosselmann S, Axt-Fliedner R, Sohn C, Kohl T . Complete chorioamniotic membrane separation with constrictive amniotic band sequence and partial extra-amniotic pregnancy: serial ultrasound documentation and successful fetoscopic intervention. J Perinatol.2014;34(12):941-4. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 14 Oct, 2025 Read the published version in BMC Pregnancy and Childbirth → Version 1 posted Editorial decision: Revision requested 09 Jun, 2025 Reviews received at journal 07 Jun, 2025 Reviews received at journal 05 Jun, 2025 Reviews received at journal 03 Jun, 2025 Reviewers agreed at journal 03 Jun, 2025 Reviews received at journal 01 Jun, 2025 Reviewers agreed at journal 01 Jun, 2025 Reviewers agreed at journal 31 May, 2025 Reviewers agreed at journal 30 May, 2025 Reviews received at journal 30 May, 2025 Reviewers agreed at journal 30 May, 2025 Reviewers agreed at journal 30 May, 2025 Reviewers invited by journal 29 May, 2025 Editor invited by journal 21 May, 2025 Editor assigned by journal 21 May, 2025 Submission checks completed at journal 21 May, 2025 First submitted to journal 19 May, 2025 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-6700418","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":464860803,"identity":"35ce130a-7b91-4214-b314-90a15e610e39","order_by":0,"name":"Shouheng Wu","email":"","orcid":"","institution":"Sichuan University","correspondingAuthor":false,"prefix":"","firstName":"Shouheng","middleName":"","lastName":"Wu","suffix":""},{"id":464860807,"identity":"930fc941-245d-4fdd-8d7b-1a0570a40a99","order_by":1,"name":"Xi Tan","email":"","orcid":"","institution":"Sichuan University","correspondingAuthor":false,"prefix":"","firstName":"Xi","middleName":"","lastName":"Tan","suffix":""},{"id":464860808,"identity":"286aad25-6063-4e2e-aeae-5ea9de646a90","order_by":2,"name":"Rong Zhou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYDACCQSD8QGElUC8FmYDkrWwSRClRX528zHpioo7dg3SPWaVP2oOM/Cz5xgw/NyBWwvjnGNpkmfOPEtukDmWdpvn2GEGyZ43Boy9Z3BrYZbIMZNsbDuczCCRfOw2Y8NhBoMbOQbMjG24tbAhtCS2Ff4EarEnpIUHqsUOZAsDL8gWCQJaJCTSki0bzhxOYAAypHmOpfNInHlWcLAXjxb5GckHbzZUHLZnkMgx/PijxlqOvz1544OfeLTAQOL+A1CXgogDhDUwMNgTo2gUjIJRMApGKAAA4QJK/FVgRG0AAAAASUVORK5CYII=","orcid":"","institution":"Sichuan University","correspondingAuthor":true,"prefix":"","firstName":"Rong","middleName":"","lastName":"Zhou","suffix":""}],"badges":[],"createdAt":"2025-05-19 15:38:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6700418/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6700418/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12884-025-08208-5","type":"published","date":"2025-10-14T15:57:39+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83815038,"identity":"e626511c-6ce7-4413-874f-44d4fda71130","added_by":"auto","created_at":"2025-06-03 07:36:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":415704,"visible":true,"origin":"","legend":"\u003cp\u003eLongitudinal section images of ultrasound at 31 weeks' gestation. These ultrasound images were made in West China Second Hospital. The amniotic bands (arrowhead in a,b,c) formed by ruptured amniotic membranes detached from the chorion (triangle in a,b,c), is close to the fetus (circle in a,b,c). The umbilical cord (star in b) enters the chorioamniotic cavity through the gap between the amniotic bands\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6700418/v1/0b295577b5561156a66bf601.png"},{"id":83814512,"identity":"bd2e6478-17b7-4978-9de4-d44af72974ba","added_by":"auto","created_at":"2025-06-03 07:28:10","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":998078,"visible":true,"origin":"","legend":"\u003cp\u003eClinical features of the patient. 3 typical amniotic bands (arrowhead)was shown in the photograph of the placenta, which were separated from the chorion(triangle). The chorionic membrane was still fused with the amniotic membrane on the fetal side of the placenta, so the patient was diagnosed with partial CMS\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6700418/v1/4e96d732de876f8b9ab6f2cc.png"},{"id":93955998,"identity":"aef0eabd-544f-44a0-8a6d-9dec235fe843","added_by":"auto","created_at":"2025-10-20 16:09:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2547309,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6700418/v1/de20fd3b-0713-4d5d-9059-98ad06a05a64.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Spontaneous partial chorioamniotic membrane separation followed by the formation of amniotic bands:a case report","fulltext":[{"header":"Background","content":"\u003cp\u003eAs we know, the fetal membranes consist of two distinct layers: the inner amniotic membrane and the outer chorionic villi, originating from different embryonic layers. These layers undergo separation before the 14th week of gestation, followed by fusion of the chorioamniotic membrane between the 14th and 16th weeks of gestation. Any separation occurring after the 16th week is considered abnormal and is known as chorioamniotic membrane separation (CMS) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Prenatal ultrasonographic findings of CMS are classified as either partial or complete, with an incidence of 0.023 to 0.534% [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Intraamniotic surgery and fetal chromosomal aneuploidy are established etiologies of CMS [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, spontaneous CMS is extremely rare. Herein, we report a case of spontaneous partial CMS followed by the formation of amniotic bands, and no case has been reported before.\u003c/p\u003e"},{"header":"Case Presentation","content":"\u003cp\u003eA 34-year-old woman with a history of four pregnancies, with one live birth through vaginal delivery seven years ago and two abortions, conceived her current pregnancy naturally. Fetal nuchal translucency measurement was within normal ranges. Non-invasive prenatal testing indicated low risk, and amniocentesis was not performed during this pregnancy. At 23 weeks of gestation, an ultrasound examination at a local hospital revealed a partial detachment of the chorioamniotic membrane for the first time, with the fetus positioned above the membrane in the amniotic cavity. Subsequent ultrasound at 27\u003csup\u003e+ 6\u003c/sup\u003e weeks of gestation indicated the presence of banded echoes in the central part of the amniotic cavity, which divided the uterine cavity into upper and lower portions. The fetus was confined to the upper part of the amniotic cavity. Unfortunately, ultrasound images from local hospitals are not available. At 31 weeks of gestation, the patient experienced irregular contractions and a slight vaginal fluid discharge. The patient was referred to West China Second Hospital, a maternal and child care center in west China. The ultrasound examination (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea,b,c) revealed that the fetus was positioned transversely and that the chorioamniotic membrane had partially detached, the uterine cavity contained 2−3 banded strong echoes. Some of these echoes were in close proximity to the fetus, which was surrounded by reduced amniotic fluid. The fetus was predominantly situated above the banded strong echoes, while the amniotic fluid was primarily located below them. Furthermore, the umbilical cord was positioned within the pool of amniotic fluid beneath the banded strong echoes. Treatment included the administration of magnesium sulfate to protect fetal cerebral nerves, dexamethasone to facilitate fetal lung maturation, and ritodrine hydrochloride to inhibit contractions. At 31\u003csup\u003e+ 5\u003c/sup\u003eweeks of gestation, the patient experienced unavoidable preterm labor. An emergency cesarean section was performed because of a transverse presentation. The neonate, a male weighing 1,810 g, exhibited no apparent malformations. Apgar scores at 1, 5, and 10 min were 6, 8, and 9, respectively. Subsequently, the neonate was intubated and transferred to the neonatal intensive care unit (NICU). Placental examination (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) indicated a partial chorionic amniotic separation with amniotic band formation. The infant received systemic treatment for 40 days in the NICU for respiratory distress syndrome before being discharged. The mother was discharged without complications one week postoperatively. Over a 10-month follow-up period, the infant was hospitalized twice for severe pneumonia. No chromosomal abnormalities, genetic disorders, or inherited metabolic disorders were identified in the infant through relevant examinations. The infant's growth and development progressed normally.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e "},{"header":"Discussion and conclusions","content":"\u003cp\u003eThe occurrence of CMS, particularly in spontaneous cases, is relatively rare. Currently, no standardized approach for managing CMS is available. Although no established grading system exists for CMS, Romain et al. proposed a classification based on the extent of separation [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The classification was as follows: \"mild\" for amniotic membrane detachment of \u0026lt; 25%, \"moderate\" for 25%−50%, and \"severe\" for \u0026gt; 50%. However, the clinical utility of this criterion for determining pregnancy outcome and fetal prognosis remains unclear.\u003c/p\u003e\u003cp\u003eThe primary cause of CMS is a medical complication resulting from invasive fetal procedures, including amniocentesis, pleurodesis, fetoscopy, or fetal surgery, which disrupt the fusion of the two membranes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. A study indicated that the occurrence of CMS following fetoscopy is approximately 40% [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The secondary cause is fetal chromosomal aneuploidy (trisomy 21, 13, and 18) or fetal connective tissue disorders (restrictive dermopathy), resulting in membrane insufficiency and incomplete chorioamniotic fusion [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Bromley et al. performed prenatal diagnosis through amniocentesis in ten patients with CMS and reported that three fetuses had Down syndrome [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Another study in 2017 identified distinct miRNA expression patterns in fetal membranes specific to tissues and regions. The miRNA expression, including miR-99a, miR-125b, and let-7c, was found to be downregulated in the fetal membranes of patients with trisomy 21. This downregulation potentially contributed to fetal membrane abnormalities associated with trisomy 21, including delayed separation of chorionic villi from the amniotic membrane or delayed fusion between chorionic villi and amniotic membrane [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Furthermore, a few cases have been associated with seromucinous collection resulting from chorionic villous hemangioma [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Joung et al. reported a case where post-cesarean section uterine scarring was proposed as a potential factor in spontaneous CMS [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Jolien suggested that endothelial rupture in preterm premature rupture of membranes (PPROM), resulting in amniotic fluid accumulation in the space between the chorionic and amniotic membranes, could be an etiology of CMS [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. However, spontaneous CMS cases without a history of invasive procedures or fetal chromosomal abnormalities are significantly rare, and the precise mechanism remains unclear. In our case, the etiology of CMS was uncertain. We excluded a history of invasive fetal surgery, fetal chromosomal abnormalities, and other uncommon causes. CMS was initially identified through ultrasound at 23 weeks of gestation at an external facility. Before the fetus is transferred to our hospital in the uterus, the amniotic membrane, previously separated, ruptured, forming amniotic band. This event did not physically injure the fetus and umbilical cord. However, the fetus was confined in an restricted environment with insufficient amniotic fluid for nearly one month. This resulted in some impairment of fetal development, particularly lung maturation, as demonstrated by respiratory distress syndrome in the newborn post-delivery and multiple lung infections during infancy.\u003c/p\u003e\u003cp\u003ePrevious studies indicate that CMS is associated with various adverse pregnancy outcomes, including miscarriage, preterm labor, fetal growth restriction, in utero fetal death, neonatal death, amniotic band syndrome, and umbilical cord complications [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Fetal malformations can result from amniotic band syndrome and/or reduced amniotic fluid levels. Previously, a study revealed a significantly higher stillbirth rate in cases of CMS occurring before 24 weeks of gestation [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. A study involving 118 instances of CMS reported that 53.1% (60/113) of deliveries resulted in preterm births, and 6.2% (7/113) in intrauterine fetal deaths. Furthermore, among 104 postpartum follow-up cases, neonatal deaths occurred in 5.8% (6/104) and infant deaths in 0.96% (1/104). The overall perinatal mortality rate (including intrauterine fetal deaths and neonatal deaths) was 11.0% (13/118) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Chorionic villus separation has been associated with an increased risk of PPROM and preterm labor [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. This is due to the normal attachment of the chorionic villus with the maternal meconium, which provides support to the amniotic membrane against physical pressures. This supportive function is lost when separation occurs, which can result in PPROM. Apart from physical factors, membrane separation can trigger preterm labor and premature rupture of membranes by releasing chemical mediators. In this case, we propose that following amniochorionic separation, the amniotic cavity ruptured, resulting in the formation of amniotic band that secured the fetus to the upper uterine region. Consequently, the amniotic fluid surrounding the fetus decreased. Remarkably, the fetus did not experience malformations, fetal distress, or umbilical cord complications, which is a very rare case. However, PPROM and preterm labor were unavoidable during hospitalization for observation.\u003c/p\u003e\u003cp\u003eThere is a lack of standardized monitoring and treatment protocols for CMS. It is recommended that, in cases of spontaneous CMS without a history of invasive fetal surgery, chromosomal analysis should be performed to exclude fetal aneuploidy. If there are no fetal chromosomal or structural abnormalities, the pregnancy can be continued with a favorable neonatal prognosis anticipated. Vigilant monitoring throughout the pregnancy is essential, including regular ultrasound assessments to monitor fetal growth, amniotic fluid levels, the presence of amniotic bands, and the potential for umbilical cord compression to evaluate fetal condition. Hospitalization for monitoring and treatment can reduce fetal mortality [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Invasive surgical intervention may be beneficial in improving neonatal outcomes by addressing the constriction caused by amniotic band formation. Schlehe documented a case in which a patient with CMS underwent fetoscopic release of amniotic bands at 24 weeks of gestation, resulting in the extension of gestation to 34 weeks [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Although our case did not involve serious complications of amniotic band syndrome, it is important to investigate the feasibility of performing amniotic band release prior to premature rupture of membranes to reduce the impact of amniotic band constriction and decreased amniotic fluid volume on fetal development.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCMS \u0026nbsp;Chorioamniotic membrane separation\u003c/p\u003e\n\u003cp\u003eNICU \u0026nbsp;neonatal intensive care unit\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePPROM \u0026nbsp;preterm premature rupture of membranes \u0026nbsp;\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is a case study, so no ethical approval was required. The informed consent of the patient involved in the article has been obtained. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe patient provided written informed consent for publication of this case report.\u0026nbsp;Moreover, the\u0026nbsp;\u003c/p\u003e\n\u003cp\u003emanuscript does not involve any personal information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article. The datasets used and/or analyzed during this study are available from the corresponding author on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e\u003cstrong\u003e\u0026rsquo;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eShouheng Wu and Rong Zhou contributed to the study conception and design. Xi Tan\u0026nbsp;carried out the data \u0026nbsp; collection. Shouheng Wu drafted the manuscript. Rong Zhou reviewed and edited the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGovaerts J, Cryns P, Jacquemyn Y. Spontaneous chorioamniotic membrane separation discovered by preterm prelabor rupture of membranes. Clin Case Rep. 2019 ;7(4):762\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eSydorak RM, Hirose S, Sandberg PL, Filly RA, Harrison MR, Farmer DL, et al. Chorioamniotic membrane separation following fetal surgery. J Perinatol.2002;22:407-10. \u003c/li\u003e\n\u003cli\u003eCorroenne R, Yepez M, Barth J, Pan E, Whitehead WE, Espinoza J,et al. Chorioamniotic membrane separation following fetal myelomeningocele repair: incidence, risks factors and impact on perinatal outcome. Ultrasound Obstet Gynecol.2020;56(5):684-93.\u003c/li\u003e\n\u003cli\u003eLevine D, Callen PW, Pender SG, McArdle CR, Messina L, Shekhar A, et al. Chorioamniotic separation after second trimester genetic amniocentesis: importance and frequency. Radiology. 1998;209:175-81.\u003c/li\u003e\n\u003cli\u003ePedreira DAL, Zanon N, Nishikuni K, Moreira de S\u0026aacute; RA, Acacio GL, Chmait RH, et al. Endoscopic surgery for the antenatal treatment of myelomeningocele: the CECAM trial. Am J Obstet Gynecol. 2016;214(1):111.e1-e11. \u003c/li\u003e\n\u003cli\u003eBromley B, Shipp TD, Benacerraf BR. Amnion-chorion separation after 17 weeks\u0026rsquo; gestation. Obstet Gynecol.1999;94(6):1024-6.\u003c/li\u003e\n\u003cli\u003eModi BP, Washington S, Walsh SW, Jackson-Cook C, Archer KJ, Strauss JF 3rd.Expression patterns of the chromosome 21 MicroRNA cluster (miR- 99a, miR-125b and let-7c) in chorioamniotic membranes. Placenta,2017;49:1-9.\u003c/li\u003e\n\u003cli\u003eEom HM, Kim YN, Choi BH, Jeong EJ, Byun JM, Jeong DH, et al. Chorioamniotic membrane separation caused by the seromucinous collection from a placental chorioangioma. Obstet Gynecol Sci. 2016;59(3):233-7.\u003c/li\u003e\n\u003cli\u003eJoung EJ, You SK, Lee JY, Ahn JW, Yun NR, Hwang SO. A live birth after spontaneous complete chorioamniotic membrane separation associated with uterine scar. Obstet Gynecol Sci.2016;59(2):144-7.\u003c/li\u003e\n\u003cli\u003eBibbo C, Little SE, Bsat J, Botka KA, Benson CB, Robinson JN.Chorioamniotic Separation Found on Obstetric Ultrasound and Perinatal Outcome. AJP Rep.2016;6(3): e337-43.\u003c/li\u003e\n\u003cli\u003eZhu KH, Young BC, Shamshirsaz AA, Espinoza J, Sanz-Cortes M, Donepudi R, et al. Outcomes of prenatally diagnosed spontaneous chorioamniotic membrane separation in singleton pregnancies: A systematic review of case series and case reports. Prenatal Diagnosis. 2020;40(11):1366\u0026ndash;74.\u003c/li\u003e\n\u003cli\u003eIshikawa G, Satomi M, Inagawa-Ichikawa T, Abe T, Akira S, Takeshita T. A case report of complete chorioamniotic membrane separation. J Nippon Med Sch.2011;78(2):120-5.\u003c/li\u003e\n\u003cli\u003eSchlehe B, Els\u0026auml;sser M, Bosselmann S, Axt-Fliedner R, Sohn C, Kohl T\u003cem\u003e.\u003c/em\u003e Complete chorioamniotic membrane separation with constrictive amniotic band sequence and partial extra-amniotic pregnancy: serial ultrasound documentation and successful fetoscopic intervention. J Perinatol.2014;34(12):941-4.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Chorioamniotic membrane separation, Amniotic band, Etiology, Pregnancy outcomes, Treatment","lastPublishedDoi":"10.21203/rs.3.rs-6700418/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6700418/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground\u003c/p\u003e\n\u003cp\u003eChorioamniotic membrane separation (CMS) is associated with various adverse pregnancy outcomes, including miscarriage, preterm labor, stillbirth, amniotic band syndrome, etc. Spontaneous CMS is extremely rare. At present, there is no standardized monitoring and treatment protocols for CMS.\u003c/p\u003e\n\u003cp\u003eCase Presentation\u003c/p\u003e\n\u003cp\u003eWe present an unusual case of spontaneous partial CMS with amniotic band diagnosed through ultrasonography at 27\u003csup\u003e+6\u003c/sup\u003eweeks of gestation in a 34-year-old woman. About one month later, an emergency cesarean section was performed because of unavoidable preterm labor and fetal transverse presentation, resulting in the successful delivery of a healthy baby. The partial CMS with amniotic band was confirmed by the examination for the placenta. The infant underwent a 10-month follow-up period and currently is in good health despite experiencing two respiratory infections.\u003c/p\u003e\n\u003cp\u003eConclusions\u003c/p\u003e\n\u003cp\u003eBased on our experience and combined with previous research, we think that etiological screening is the primary priority for CMS cases. Expectant management under close ultrasonographic scans and prolonging gestational age as much as possible may be beneficial for neonatal prognosis.\u003c/p\u003e","manuscriptTitle":"Spontaneous partial chorioamniotic membrane separation followed by the formation of amniotic bands:a case report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-03 07:28:05","doi":"10.21203/rs.3.rs-6700418/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-09T04:43:14+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-08T00:01:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-06T00:50:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-03T19:46:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"226755124395689108929324242832890443113","date":"2025-06-03T19:38:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-01T07:25:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"33957593173730617789151265949052178680","date":"2025-06-01T05:45:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"100097993292045940744857065508714089738","date":"2025-05-31T04:02:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"139340401846475961066525700253566177679","date":"2025-05-30T23:13:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-30T13:51:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"136895022282852590319588582950465887798","date":"2025-05-30T13:19:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"95860210091028311331533682766094676785","date":"2025-05-30T11:25:26+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-29T23:43:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-05-21T15:07:33+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-21T11:56:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-21T11:52:44+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pregnancy and Childbirth","date":"2025-05-19T15:25:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"26a51080-f296-42cf-ac6b-eee06bfa560b","owner":[],"postedDate":"June 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-20T16:01:55+00:00","versionOfRecord":{"articleIdentity":"rs-6700418","link":"https://doi.org/10.1186/s12884-025-08208-5","journal":{"identity":"bmc-pregnancy-and-childbirth","isVorOnly":false,"title":"BMC Pregnancy and Childbirth"},"publishedOn":"2025-10-14 15:57:39","publishedOnDateReadable":"October 14th, 2025"},"versionCreatedAt":"2025-06-03 07:28:05","video":"","vorDoi":"10.1186/s12884-025-08208-5","vorDoiUrl":"https://doi.org/10.1186/s12884-025-08208-5","workflowStages":[]},"version":"v1","identity":"rs-6700418","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6700418","identity":"rs-6700418","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}