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.
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 0.5-1%. 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 three days of the procedure. However, in some cases, it can occur up to two weeks later. There's no evidence that you can do anything during this time to reduce your risk.
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 used to guide the needle, significantly reducing the risk of injury.
As with all surgical procedures, there's a risk of infection during or after amniocentesis. However, the rate of severe infection for amniocentesis is lower than 1 in 1,000.
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.
Read more about preventing rhesus disease.
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 isn't recommended before 15 weeks of pregnancy.