{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T21:42:18Z","timestamp":1791754938620,"version":"4.3.4"},"reference-count":20,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2021,2,2]],"date-time":"2021-02-02T00:00:00Z","timestamp":1612224000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Birth Defects Research"],"published-print":{"date-parts":[[2021,4]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>Acardiac twinning is a complication of monochorionic twin pregnancies. From literature reports, 30 of 41 relatively large acardiac twins with renal tissue produced polyhydramnios within their amniotic compartment. We aim to investigate the underlying mechanisms that cause excess amniotic fluid using an established model of fetal fluid dynamics.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We assumed that acardiac onset is before 13\u2009weeks, acardiacs with renal tissue have normal kidney function and produce urine flow from 11\u2009weeks on, and acardiac urine production requires a pressure of half the pump twin's mean arterial pressure. We apply a resistance network with the pump twin's arterio\u2010venous pressure as source, pump umbilical arteries, placenta, placental arterio\u2010arterial (AA) anastomoses and acardiac resistances. Acardiac amniotic fluid dynamics excluded acardiac lung fluid secretion, swallowing and the relatively small intramembranous flow.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>In small acardiacs with sufficient urine production, polyhydramnios will occur due to the lack of amniotic fluid resorption. Urine production is dependent upon having sufficient mean arterial pressure, which requires nearly a two\u2010fold larger resistance within the acardiac as compared to the placental AA resistance. Subphysiologic arterial pressure may result in renal dysgenesis.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Our findings suggest the potential for prediction of which clinical acardiac cases may or may not develop polyhydramnios based upon noninvasive assessments of renal tissue, blood flow and urine production. This information would be of great value in determining early obstetric interventions as opposed to conservative management. These findings may also contribute to an improved knowledge of the fascinating pathophysiology that surrounds acardiac twinning.<\/jats:p><\/jats:sec>","DOI":"10.1002\/bdr2.1874","type":"journal-article","created":{"date-parts":[[2021,2,6]],"date-time":"2021-02-06T04:28:49Z","timestamp":1612585729000},"page":"500-510","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Acardiac twin pregnancies part V: Why does an acardiac twin with renal tissue produce polyhydramnios?"],"prefix":"10.1002","volume":"113","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3747-6219","authenticated-orcid":false,"given":"Martin J. C.","family":"van Gemert","sequence":"first","affiliation":[{"name":"Department of Biomedical Engineering &amp; Physics Amsterdam University Medical Centra, Location AMC  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter G. J.","family":"Nikkels","sequence":"additional","affiliation":[{"name":"Department of Pathology, Wilhelmina Children's Hospital University Medical Center  Utrecht The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael G.","family":"Ross","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology Harbor UCLA Medical Center  Torrance California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6648-8967","authenticated-orcid":false,"given":"Jeroen P. H. M.","family":"van den Wijngaard","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry Hematology and Immunology Diakonessenhuis  Utrecht The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2021,2,2]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.2147\/IJWH.S72178"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471-0528.1968.tb01551.x"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1161\/01.RES.70.4.761"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471-0528.1902.tb15905.x"},{"key":"e_1_2_8_6_1","doi-asserted-by":"publisher","DOI":"10.1002\/tera.1420500306"},{"key":"e_1_2_8_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ajog.2010.04.018"},{"key":"e_1_2_8_8_1","doi-asserted-by":"publisher","DOI":"10.1002\/uog.14766"},{"key":"e_1_2_8_9_1","doi-asserted-by":"publisher","DOI":"10.1007\/s10024-004-7084-0"},{"key":"e_1_2_8_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/0002-9378(90)91094-S"},{"key":"e_1_2_8_11_1","doi-asserted-by":"publisher","DOI":"10.1007\/s100249900086"},{"key":"e_1_2_8_12_1","doi-asserted-by":"publisher","DOI":"10.1080\/jmf.10.1.2.19"},{"key":"e_1_2_8_13_1","doi-asserted-by":"publisher","DOI":"10.1152\/ajpendo.1986.250.5.E564"},{"key":"e_1_2_8_14_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1447-0756.1984.tb00026.x"},{"key":"e_1_2_8_15_1","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.2001.280.5.R1499"},{"key":"e_1_2_8_16_1","first-page":"285","article-title":"Twin reversed arterial perfusion (TRAP) sequence: A study of 14 twin pregnancies with acardiacus","volume":"7","author":"Van Allen M. 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