What It Checks For

Amniocentesis tests for genetic conditions including Down's syndrome, Edwards' syndrome, Patau's syndrome, sickle cell disease, thalassaemia, and cystic fibrosis.

Who It May Be Offered To

You may be offered amniocentesis if your baby has a higher chance of one of these conditions — for example, if an earlier screening test suggested this, if a previous pregnancy or child was affected, or if you, the baby's father, or a close relative carries one of these conditions.

What Happens

The procedure is carried out by an obstetrician, usually in hospital, and takes about 10 minutes. You're welcome to ask for a chaperone in the room if you'd like.

The main steps are:

1. An ultrasound scan lets the doctor see your baby on screen throughout
2. Your tummy is cleaned with antiseptic
3. A thin needle is guided through your tummy into the womb using the ultrasound image — this may feel uncomfortable but shouldn't be painful
4. A small sample of the amniotic fluid is collected
5. The needle is carefully removed
6. The sample is sent to a lab for testing

If you're expecting more than one baby, samples may need to be taken from the fluid around each.

Afterwards

A tummy ache in the first day or two is normal and can usually be eased with paracetamol. It's worth resting for the following day if possible. If your blood type is rhesus negative, you'll be offered an injection to protect your baby from a condition called haemolytic disease of the foetus and newborn.

Things to Weigh Up

As with any procedure, amniocentesis carries some risks, which your maternity team will talk through to help you decide whether it's right for you.

Miscarriage

There's a risk of miscarriage of around 1 in every 200 pregnancies, rising if you're carrying twins or more. Most miscarriages linked to the procedure happen within 3 days, though it can occur up to 2 weeks afterwards.

Passing on Infection

If you're HIV positive, or have hepatitis B or C, amniocentesis may slightly increase the risk of passing the infection to your baby — your care team can discuss this with you in more detail.

Infection

Rarely, the procedure itself can cause an infection, affecting fewer than 1 in 1,000 procedures.

When You'll Know

Results for Down's syndrome, Edwards' syndrome and Patau's syndrome are usually available within about 3 working days; if your baby is being tested for other conditions, this can take around 2 weeks. You can usually choose to get your results by phone or in person.

If a Condition is Found

Should the results show your baby has a condition, your doctor and midwife will talk you through what this means and the choices available, including continuing the pregnancy with additional support, or ending it.

Getting Support

Organisations such as Antenatal Results and Choices (ARC) offer information and emotional support around screening results, alongside condition-specific charities including the Down's Syndrome Association, the Sickle Cell Society, SOFT UK, and Shine.