Pregnancy loss rate after mid-trimester amniocentesis in twin pregnancies

Objective: The purpose of this study was to estimate the attributable pregnancy loss rate of mid-trimester amniocentesis in twin pregnancies. Study Design: A 16-year retrospective cohort of all twin pregnancies that underwent ultrasound evaluation at a large tertiary care medical center was followed for pregnancy outcomes. Women who underwent amniocentesis were compared with those who did not. Fetal loss was defined as loss before 24 weeks' gestation. Univariable, stratified, multivariable, and time-to-event analyses were performed. Results: Of 1934 twin pregnancies, 311 women elected amniocentesis. Women who elected amniocentesis were more likely to experience a pregnancy loss than those who did not (3.2% vs 1.4%; risk difference, 1.80%; 95% CI, -0.24 to 3.84%), which was significant after adjustment for advanced maternal age, chorionicity, sonographic findings, alcohol exposure, and race (adjusted odds ratio, 2.9; 95% CI, 1.2-6.9). Conclusion: The attributable risk of pregnancy loss before 24 weeks' gestation after mid-trimester amniocentesis in twin pregnancies is 1 in 56 (1.8%). This information will be useful in counseling patients with twin pregnancies who are considering amniocentesis.