Is amniocentesis risky?

There is a small risk, and it is smaller than most people expect. RCOG guidance states that the additional risk of miscarriage following amniocentesis performed by an appropriately trained operator is likely to be below 0.5% — around 1 in 200 or lower. Older patient information often quotes 1 in 100, which reflects data from before improvements in ultrasound guidance and technique. Systematic review data cited in the guideline put the procedure-related loss even lower in several analyses — 0.11% in one pooled estimate, with six of ten studies reporting 0.2% or less. Other risks, all uncommon: leaking of amniotic fluid, which usually settles; infection, which is rare; and needing a repeat sample if insufficient cells are obtained. Severe maternal complications have been reported but in very small numbers. What actually affects your risk: Operator experience — ISUOG documents lower loss rates where more than 100 procedures are performed annually. It is entirely reasonable to ask. Number of attempts — three or more punctures increases risk. Certain factors including a bloody or discoloured sample, which reflects bleeding within the sac. For twins, the additional risk is around 1%. Amniocentesis should not be performed before 15+0 weeks — RCOG grades this a strong recommendation. If you are Rh negative, you will need anti-D afterwards. The procedure is performed under continuous ultrasound guidance, so the needle is watched throughout.