Amniocentesis is a fairly common and safe procedure.

For most women, the benefits of having amniocentesis – in terms of diagnosing problems with the developing baby – significantly outweigh the risks.

However, you should be aware of the possible complications during or after amniocentesis so you can make an informed decision. These are outlined below.

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

In very rare cases, an infection may develop if the procedure introduces bacteria into your amniotic sac (the sac surrounding the foetus, which contains amniotic fluid). This can cause:

• a high temperature (fever) of 38ºC (100.4ºF) or above
• tenderness of your abdomen (tummy)
• contractions (when your abdomen tightens then relaxes)

You should seek immediate medical attention if you have any of these symptoms. The risk of developing a serious infection from amniocentesis is estimated to be less than 1 in 1,000.

Rhesus disease

Rhesus disease is a condition where proteins in a pregnant woman's blood attack her baby's blood cells.

Rhesus disease is only possible if your blood is rhesus negative and your baby's blood is rhesus positive. If this is the case, amniocentesis could trigger rhesus disease if your blood is exposed to your baby's blood during the procedure.

In this situation, you'll be given an injection of anti-D immunoglobulin after having amniocentesis. Immunoglobulin is a solution of antibodies (proteins produced by the body to fight disease-carrying organisms) that can prevent rhesus disease from developing.

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.

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 in 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. 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 the first 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.

Chromosomes are the threadlike structures inside cells that carry genetic information in the form of genes.

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.