Updated June 23, 2014.

Question: What's the Real Risk of Miscarriage After an Amniocentesis?

Amniocentesis is a prenatal test in which the doctor inserts a needle into the uterus through a pregnant woman's abdomen and draws out a sample of the amniotic fluid in order to perform tests on the baby's chromosomes or to check markers of other health conditions. Different sources cite a different level of risk for miscarriage after an amniocentesis.

Which one is correct?

Answer:

Many women are terrified of amniocentesis because it carries a small risk of causing a miscarriage, such as if the needle would cause an infection. Most sources cite the risk of miscarriage after an amniocentesis to be around 0.5% to 1%. Although that's a low risk in most situations, a 1 in 200 chance of losing their babies because of an informational test is understandably unacceptable for many pregnant women.

But there's some evidence that the those number may not be accurate for modern techniques and methods. A widely reported 2006 study found evidence that the real added miscarriage risk of amniocentesis might only be 0.06% -- which equates to 1 in 1,600. The researchers took into account that women who opted for amniocentesis might have already been more likely to miscarriage for reasons unrelated to the test, such as a higher maternal age or having had a positive screening test for abnormalities, and that miscarriages that occurred after an amniocentesis might not always be attributable to the procedure itself.

After that study, the Washington University School of Medicine analyzed its own information from 1990 to 2006 and found that the added risk of miscarriage after an amniocentesis was only 0.13% -- 0.97% of women who had an amniocentesis before 24 weeks had a spontaneous late miscarriage or preterm birth, but this also happened in 0.84% of women who did not have an amniocentesis. They concluded that the difference was not statistically significant.

So amniocentesis may not be as risky as many have believed. But it's hard to make any kind of sweeping generalizations about the risk because it might vary by the individual's situation and also by the skill of the practitioner performing the test. If you are considering an amniocentesis for any reason and you are worried about the risk of miscarriage, it is OK to ask your practitioner about his or her level of experience and any other questions that may be on your mind.

<sub>Sources:

Eddleman, Keith A., Fergal D. Malone, Lisa Sullivan, Kim Dukes, Richard L. Berkowitz, Yara Kharbutli, T. Flint Porter, David A. Luthy, Christine H. Comstock, George R. Saade, Susan Klugman, Lorraine Dugoff, Sabrina D. Craigo, Ilan E. Timor-Tritsch, Stephen R. Carr, Honor M. Wolfe, Mary E. D’Alton, "Pregnancy Loss Rates After Midtrimester Amniocentesis." Obstetrics & Gynecology 2006. Accessed 17 Sept 2008.

Gioriandino, Claudio, "After midtrimester amniocentesis the risk of spontaneous pregnancy loss was 6 per 10 000." Evidence-Based Medicine 2007. Accessed 17 Sept 2008.

Odibo, Anthony O., Diane L. Gray, Jeffrey M. Dicke, David M. Stamilio, George A. Macones, and James P. Crane, "Revisiting the Fetal Loss Rate After Second-Trimester Genetic Amniocentesis." Obstetrics & Gynecology 2008. Accessed 17 Sept 2008.

Royal College of Obstetricians and Gynaecologists, "Amniocentesis: What You Need to Know." 2006. Accessed 17 Sept 2008.</sub>