Amniocentesis

Category: Women's Health & Childbirth · All women's health & childbirth

What it is

Amniocentesis is a diagnostic test in pregnancy: under continuous ultrasound guidance, a fine needle passes through the abdomen into the womb to take a small sample of the fluid around the baby, which contains the baby's cells for genetic and infection testing.

Why it is done

It is offered when screening suggests a higher chance of a chromosomal condition (such as Down's syndrome), for known genetic conditions in the family, certain infections, and some other fetal concerns. It is usually performed from 15 weeks of pregnancy.

How to prepare

You will have counselling about what the test can and cannot detect, result times, and the procedure-related miscarriage risk, so you can decide freely. Blood group is checked — anti-D is given if you are Rh-negative. No fasting is needed.

What happens during the procedure

After cleaning the abdomen, the needle is guided into a pocket of fluid away from the baby and placenta, and about 15 to 20 ml is drawn off. Local anaesthetic is sometimes used. Most women describe pressure and brief cramping; it takes a few minutes.

Afterwards — recovery & results

Rest for the remainder of the day and avoid heavy exertion for a day or two. Mild cramping is common; report pain, bleeding, fluid leaking or fever promptly. Rapid results for the common chromosomal conditions usually take a few days, with full culture/array results in about two weeks.

Risks & considerations

Amniocentesis carries a small procedure-related risk of miscarriage — contemporary figures are generally quoted at around 1 in 200 to 1 in 900 procedures in experienced hands; your unit will give its own audited figure. Other risks include infection, fluid leak and injury to the baby (rare with continuous ultrasound guidance).

Frequently asked questions

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