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Second-Trimester Amniocentesis Is Even Safer Than We Thought

In one prenatal diagnosis center, the pregnancy loss rate attributed to amniocentesis was 1 in 769 procedures.

Prenatal genetic testing is an important diagnostic tool; however, both clinicians and parents rightfully worry about the possibility of fetal loss when such procedures are invasive. Investigators at Washington University School of Medicine conducted a retrospective cohort study based on 16 years of practice history at their prenatal diagnosis clinic. Pregnancy outcomes in 12,000 women who underwent amniocentesis at 15 to 22 weeks’ gestation were compared with those in 40,000 women who did not undergo invasive procedures. Women with multiple gestations and those who had chorionic villus sampling before 15 weeks were excluded.

Overall, 0.97% of women who underwent amniocentesis suffered spontaneous fetal loss before 24 weeks’ gestation, compared with 0.84% of women not having amniocentesis. Including induced labors, the pregnancy loss rate attributed to amniocentesis was 0.13% — or 1 in 769 procedures. In analysis adjusted for confounding variables (maternal age, race, smoking or alcohol use, prior fetal loss, presence of fetal anomaly or chromosomal abnormality, and abnormal serum screen for aneuploidy), the rate of fetal loss before 24 weeks’ gestation did not differ significantly between women who underwent amniocentesis and those who had no invasive procedures. Women with normal second-trimester serum aneuploidy screens who underwent amniocentesis were the only subgroup to experience significantly more fetal loss compared with women in the same subgroup who had no procedures (0.97% vs. 0.80%; P=0.03).

Comment: Clinicians can feel confident in recommending second-trimester amniocentesis as safe and beneficial for both mother and fetus. The long-held amniocentesis-associated fetal loss rate of 1 in 200 procedures has been challenged before (Journal Watch Women’s Health Apr 4 2006 and Jan 11 2007); perhaps we can now amend it to 1 in 700. However, the authors examined fetal loss rates only at their own facility — therefore, other prenatal diagnosis centers should assess their own performances independently.

— Sandra Ann Carson, MD

Published in Journal Watch Women's Health April 24, 2008

Citation(s):

Odibo AO et al. Revisiting the fetal loss rate after second-trimester genetic amniocentesis: A single center’s 16-year experience. Obstet Gynecol 2008 Mar; 111:589.

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