Risks of third-trimester amniocentesis.

Objective: To establish the risk of immediate complications from third-trimester amniocentesis.

Study Design: The entry criterion was amniocentesis done in the third trimester (28 or more weeks of gestation). The primary study outcome was any complication within 24 hours after the procedure. The secondary outcome was mode of delivery and pregnancy outcome.

Results: One hundred eleven patients were enrolled in this study with a known postprocedure course and pregnancy outcome. The average patient age was 29.8 years, average gravidity 2.9, average gestational age 36 weeks, average amount of amniotic fluid withdrawn 12.9 mL and average number of attempts to perform amniocentesis 1.03. The most common indication for the procedure was fetal lung maturity study and workup for chorioamnionitis. The list of complications observed within 24 hours included: regular contractions (2 patients, or 1.8%), ruptured membranes (1 patient, or 0.9%) and minimal vaginal bleeding (1 patient, or 0.9%). The overall complication rate was 3.6%. There was no perinatal or maternal morbidity directly linked to the procedure. No patients with complications needed urgent delivery.

Conclusion: Third-trimester amniocentesis carried a complication rate of 3.6%. All complications were self-limited.