Obstetrics• Updated 21 October 2026
Amniocentesis
A diagnostic test in pregnancy that takes a small sample of the fluid around the baby to check its chromosomes.
Results: 2–3 weeks (rapid results sooner) Specimen: Amniotic fluid
Quick Summary
Primary Purpose
To diagnose chromosomal and some genetic conditions after a high-chance screening result.
What It Measures
The baby's chromosomes or specific genes.
Preparation
No special preparation; counselling beforehand.
Overview
Usually done after 15 weeks.
There's a small risk of miscarriage.
What It Measures
Chromosomes
Number and structure.
How It's Performed
- 01
Ultrasound guidance
To find a safe spot.
- 02
Needle
A thin needle through the tummy.
- 03
Rest
Take it easy for a day.
Interpreting Results & Next Steps
Discuss with Doctor
Your doctor will explain what your result means and what happens next.
If values are High:
Results confirm or rule out the condition.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Amniocentesis (amniotic fluid test)(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Amniocentesis(opens in a new tab) · NHS