Ramifications of third trimester amniocentesis in twin pregnancies: a retrospective cohort study

Background: To determine the association between gestational age at amniocentesis and procedure-related complications in twin gestations. Methods: : A retrospective cohort study of all twin gestations that underwent amniocentesis in a tertiary hospital between 2007 and 2016. Outcomes and procedure related complications were compared between third trimester (≥24 weeks) and mid-trimester amniocentesis (16-23 weeks). Results: Compared to mid-trimester amniocentesis (n=157 (84.9%)), the third trimester group (n=28 (15.1%)) was younger (31.5 vs. 35.3 years, p<0.001) and presented with more fetal growth restriction (28% vs. 10% p=0.015). Membrane rupture within 4 weeks of amniocentesis was significantly higher in the third trimester amniocentesis group (31% vs. 1%, p<0.001). Multivariate analysis suggested gestational age at amniocentesis as an independent risk factor for premature rupture of membranes within 4 weeks of amniocentesis. Conclusions: : Third trimester amniocentesis in twin pregnancies is associated with significantly higher rates of procedure related membrane rupture compared to mid-trimester amniocentesis.