The risk of second-trimester amniocentesis in twin gestations: a case-control study

Pregnancy outcomes in patients with twin pregnancy undergoing second-trimester amniocentesis for fetal karyotype assessment were compared in a case-control study with twin pregnancies undergoing routine ultrasonographic studies at similar gestational ages.

All spontaneous and induced twin gestations that underwent ultrasonographic examination between 14 and 20 weeks were compiled for the period January 1987 through January 1992. Patients having undergone multifetal reduction or chorionic villous sampling and those with fetal anatomic or chromosomal anomalies, discordant growth (> 20%), death, or a monoamniotic sac detected at ultrasonography were excluded.

The mean (+/- SD) maternal age was significantly higher among the 101 cases than among the 108 controls (35.2 +/- 3.5 vs 30.4 +/- 5.3 years, respectively; p < 0.01). No differences were noted in gravidity, parity, number of prior spontaneous losses, or gestational age at ultrasonography between the two groups. The fetal loss rate was similar among cases and controls (seven of 202 [3.5%] vs seven of 216 [3.2%], relative risk 1.07, 95% confidence intervals 0.3 to 3.5). No losses occurred within 3 weeks of the procedure. Gestational age at delivery, birth weight, mean Apgar scores at 1 and 5 minutes, and length of neonatal stay were not significantly different between cases and controls.

Second-trimester amniocentesis in twin pregnancies is apparently not associated with excess pregnancy loss.