Risks of amniocentesis 

Before you decide to have amniocentesis, you'll be told about the risks and possible complications.

The main risks associated with the procedure are outlined below.

Miscarriage

There's a small risk of miscarriage (loss of the pregnancy) occurring in any pregnancy, regardless of whether or not you have amniocentesis.

If you have amniocentesis after 15 weeks of pregnancy, the chance of having a miscarriage is estimated to be about 1%. The risk is higher if the procedure is carried out before 15 weeks.

It's not known for certain why amniocentesis can lead to a miscarriage. However, it may be caused by factors such as infection, bleeding or damage to the amniotic sac that surrounds the baby.

Most miscarriages that happen after amniocentesis occur within 72 hours of the procedure. However, in some cases a miscarriage can occur later than this (up to two weeks afterwards).

Inconclusive results

After having amniocentesis, it can be reassuring if the results indicate that your developing baby has normal chromosomes and that there are no signs of any developmental problems.

However, you should be aware that amniocentesis can't test for every condition or disease, and it can't guarantee your baby will be born completely healthy.

Read more about the results of amniocentesis

Injury from the needle

During amniocentesis, the placenta (the organ that links the mother's blood supply to her unborn baby's) may be punctured by the needle.

It's sometimes necessary for the needle to enter the placenta to access the amniotic fluid. If this happens, the puncture wound usually heals without any more problems developing.

An ultrasound scanner is now commonly used to guide the needle, significantly reducing the risk of injury.

Infection

As with all types of surgical procedures, there's a risk of infection during or after amniocentesis. Infection can occur if there are bacteria on your skin or on the instruments being used.

However, severe infection occurs in less than 1 in every 1,000 procedures.

Rhesus disease

If your blood type is rhesus (RhD) negative, but your baby's blood type is RhD positive, it's possible for sensitisation to occur during amniocentesis.

This is where some of your baby's blood enters your bloodstream and your body starts to produce antibodies to attack it. If it's not treated, this can cause the baby to develop rhesus disease.

If you don't already know your blood type, a blood test will be carried out before amniocentesis to see if there's a risk of sensitisation. An injection of a medication called anti-D immunoglobulin can be given to stop sensitisation occurring, if necessary.

Read more about preventing rhesus disease.

Club foot

Having amniocentesis early (before week 15 of the pregnancy) has been associated with an increased risk of the unborn baby developing club foot.

Club foot, also known as talipes, is a deformity of the ankle and foot that's present at birth (congenital).

Because of the increased risk of a baby developing club foot, amniocentesis isn't recommended before 15 weeks of pregnancy.

Page last reviewed: 21/04/2016

Next review due: 01/04/2019