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Risks

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 loss of the pregnancy (miscarriage) 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 up to 1 in a 100.

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. But 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 3 days of the procedure. But in some cases it can occur up to 2 weeks later.

There's no evidence that you can do anything during this time to reduce your risk.

Infection

As with all surgical procedures, there's a risk of infection during or after amniocentesis.

But the rate of severe infection for amniocentesis is lower than 1 in 1,000.

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 do not 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.

Find out 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 congenital (present at birth) deformity of the ankle and foot.

Because of the increased risk of a baby developing club foot, amniocentesis is not recommended before 15 weeks of pregnancy.