Amniocentesis and CVS: the risk is much lower than you were told
The old one-in-two-hundred figure is out of date.
Chorionic villus sampling takes a small sample of placenta, usually between 10 and 13 weeks. Amniocentesis takes a sample of the fluid around the baby, usually after 15 weeks. Both give a definite answer about the chromosomes.
Both were long quoted as carrying a 1 in 200 risk of miscarriage. Modern analyses do not support that.
| Analysis | Procedure-related loss, amniocentesis | Procedure-related loss, CVS |
|---|---|---|
| Meta-analysis, 51,615 procedures | 0.11% (95% CI −0.04 to 0.26) | 0.22% (95% CI −0.71 to 1.16) |
| Updated meta-analysis | 0.30% (95% CI 0.11 to 0.49) | 0.20% (95% CI −0.13 to 0.52) |
| Same, restricted to best-matched comparisons | 0.12% (95% CI −0.05 to 0.30) | −0.11% (95% CI −0.29 to 0.08) |
Several of those confidence intervals cross zero, meaning no excess risk could be detected at all. The honest summary is that the procedure-related risk is somewhere around 1 to 3 per 1,000, and possibly lower.
Why this matters for your decisionWomen decline diagnostic testing, and act on screening results instead, largely because of a risk figure that is roughly four times too high.
Where this comes from:
152. Akolekar R, Beta J, Picciarelli G, Ogilvie C, D'Antonio F. Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2015;45(1):16-26.
153. Salomon LJ, Sotiriadis A, Wulff CB, Odibo A, Akolekar R. Risk of miscarriage following amniocentesis or chorionic villus sampling: systematic review of literature and updated meta-analysis. Ultrasound Obstet Gynecol. 2019;54(4):442-451.
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