Background: Recent studies have debated the safety of early amniocentesis, one of which reported a significant increase in spontaneous fetal losses following amniocentesis performed at 10-13 weeks of gestation. The aim of this study was to determine the fetal loss rate following amniocentesis performed at different stages in the second trimester.
Methods: One thousand six hundred and fifty-one consecutive amniocenteses undertaken in a low risk population between 13 weeks+0 days and 20 weeks+6 days were evaluated. In 87% of the women the reason for testing was maternal age (mean 37.1 years). Data concerning patients, procedure details and pregnancy outcome were recorded.
Results: Spontaneous abortion before 28 weeks of gestation occurred in 1.1%, one third of which were within two weeks and the remaining within seven weeks after the procedure. The fetal loss rate was higher when the amniocentesis was performed earlier in pregnancy, at 13 weeks+0 days exceeding 3%. Abnormal color of the amniotic fluid and leakage of amniotic fluid were strong predictors of fetal loss. Transplacental needle insertion did not increase the risk of pregnancy loss.
Conclusion: Amniocentesis performed very early in the second trimester is followed by an increased fetal loss rate that cannot be explained solely by a higher risk of spontaneous abortion at this time of gestation.