Pregnancy outcomes after late second trimester amniocentesis for prenatal diagnosis

Objective: To compare the rate of preterm delivery in patients who had an amniocentesis before and after 20 weeks gestation. Study Design: This is a single-center retrospective cohort study of patients referred for specialized sonogram between January 1, 2007 and December 31, 2009. Outcomes of patients who underwent amniocentesis at less than 20 0/7 weeks were compared to those who had amniocentesis on or after 20 0/7 weeks. Results: 1041 patients met the inclusion criteria, and 290 (27.9%) underwent amniocentesis. Women were younger in the late amniocentesis group and were more likely to be African-American. Gestational age at delivery, rate of preterm birth,, and birth weight did not differ between the two groups. In a multivariate analysis, gestational age at amniocentesis was not a significant factor for gestational age at delivery. Conclusion: Amniocentesis performed after 20 weeks gestation appears to be safe. This study provides reassuring information regarding late amniocentesis.