Unfused amnion and chorion after 14 weeks of gestation: associated fetal structural and chromosomal abnormalities

Abstract

AbstractObjectiveTo assess possible associations between delayed chorioamniotic fusion after the end of the first trimester and fetal structural and/or chromosomal abnormalities.DesignWe prospectively studied 492 fetuses from high‐risk pregnancies between 14 and 18 weeks of gestation by transabdominal ultrasonography. Of these, 60 (12%) had unfused amnion and chorion.ResultsNo additional abnormalities were detected in 28/60 fetuses (47%). Karyotyping was performed in 27/28 cases, and one fetus had trisomy 13 (4%). Ten of 24 fetuses (42%) of this group attending a second mid‐trimester scan after 18 weeks of gestation had abnormal sonographic findings not noted at the initial scan. Thirty‐two of 60 (53%) fetuses had additional abnormalities at the initial scan: cystic hygroma (n = 12), increased nuchal translucency (n = 10) and other abnormalities (n = 10). Karyo‐typing revealed aneuploidy in 13 of 28 fetuses (46%) tested: trisomy 21 (n = 5), Turner's syndrome (n = 3), trisomy 18 (n = 3) and trisomy 13 (n = 2). Additional fetal abnormalities were detected only at the second scan after 18 weeks of gestation in three of eight fetuses (38%).ConclusionsThese preliminary data suggest that the sonographic finding of unfused amnion and chorion after 14 weeks of gestation may be associated with fetal structural and/or chromosomal abnormalities. Copyright © 1999 International Society of Ultrasound in Obstetrics and Gynecology