Screening
Amniocentesis
Amniocentesis is a diagnostic test in pregnancy that takes a small sample of the fluid around the baby to check for chromosomal and genetic conditions.
Quick answer
Amniocentesis: what it is and what the results mean
Amniocentesis involves passing a thin needle through the abdomen, guided by ultrasound, to collect a small sample of the amniotic fluid surrounding the baby. The fluid contains the baby’s cells, which can be tested for genetic conditions.
- Why it is done: It is offered as a diagnostic test, usually after a higher-chance screening result, to confirm or rule out conditions such as Down’s syndrome and certain inherited disorders.
- Understanding results: Because it tests the baby’s own cells, amniocentesis gives a diagnostic (yes or no) answer for the conditions checked, allowing informed decisions and planning for the rest of the pregnancy.
What it is
Amniocentesis involves passing a thin needle through the abdomen, guided by ultrasound, to collect a small sample of the amniotic fluid surrounding the baby. The fluid contains the baby’s cells, which can be tested for genetic conditions.
Why it is done
It is offered as a diagnostic test, usually after a higher-chance screening result, to confirm or rule out conditions such as Down’s syndrome and certain inherited disorders. It gives a definite answer rather than a chance.
What to expect
It is usually done after 15 weeks. Using ultrasound guidance, a fine needle is passed through the tummy to take the fluid sample; it may feel like a period-type cramp. Initial results can come within a few days, with full results later.
Understanding the results
Because it tests the baby’s own cells, amniocentesis gives a diagnostic (yes or no) answer for the conditions checked, allowing informed decisions and planning for the rest of the pregnancy.
Good to know
Risks and limitations
It carries a small risk of miscarriage, which your team will explain, along with rare risks of infection or leaking fluid. Because of this, it is offered as a choice, usually after screening suggests a higher chance.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Amniocentesis: frequently asked questions
What is the risk of miscarriage with amniocentesis?
There is a small additional risk, which your specialist will explain in detail based on current figures. Because of this risk, the test is a personal choice, usually offered after higher-chance screening.
How is amniocentesis different from NIPT?
NIPT is a screening blood test that estimates chance with no risk to the pregnancy, while amniocentesis is a diagnostic test that gives a definite answer but carries a small procedure risk.
Related tests
Other screening investigations
Sources
Where this is drawn from
- NHS — Screening and pregnancy
- NICE — antenatal and screening guidance
- UK National Screening Committee
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