The Impact of Delayed Fusion of Amnion and Chorion on Maternal and Fetal Outcomes: A Prospective Cohort Study.

OBJECTIVE

To assess the association between delayed fusion of the amniotic and chorion diagnosed at 16 weeks of gestation and maternal-fetal outcomes.

METHODS

This prospective cohort study was conducted at Tianjin Central Hospital of Gynaecology Obsterics, China, from February 2022 to March 2024. A total of 331 singleton pregnant women with low risk of fetal chromosomal abnormalities were enrolled. Ultrasound examinations at 16 weeks' gestation identified cases of delayed fusion of amnion and chorion. Maternal and fetal outcomes were compared between the delayed fusion group and the timely fusion group.

RESULTS

Delayed fusion occurred in 28.00% (91/325) of cases. Post-delivery fetal membrane histopathology revealed no structural abnormalities attributable to delayed fusion. No significant differences were observed in maternal complications (gestational diabetes mellitus, hypertensive disorders, obesity, anemia) and 5-minute Apgar scores between groups. In addition, miscarriage rates were unaffected by delayed fusion. Notably, the delayed fusion group had a significantly higher incidence of preterm births (8.79% (8/91) vs. 2.56% (6/234), P = 0.028). After adjustment for confounders, infants in the delayed fusion group had a significantly lower mean birth weight (172.05 g less) than those in the timely fusion group.

CONCLUSION

Delayed fusion at 16 weeks did not alter fetal membrane structure after delivery and was not associated with most maternal or neonatal complications in this cohort. However, it may be an independent risk factor for preterm birth and reduced birth weight, warranting further investigation.