Amniocentesis
Overview
Amniocentesis is a very accurate diagnostic test used to identify certain birth defects and genetic conditions in a fetus.
During the procedure, a small sample of the amniotic fluid surrounding the fetus in the uterus is drawn for testing.
You may choose to have an amniocentesis if your health-care provider says you are at risk of having a baby with conditions such as the following.
- Down syndrome
- Trisomy 18
- Cystic fibrosis (CF)
- Spina bifida
- And others
More about amniocentesis
Amniocentesis can be performed by an obstetrician (OB) after you are 15.5 weeks pregnant. The procedure takes about five minutes and is followed by a 30-minute resting period.
Using ultrasound for guidance, the OB will carefully insert a thin needle through your belly and into your uterus to remove about one tablespoon of amniotic fluid from the area around the fetus. Removing this small amount of fluid is harmless to both you and the fetus.
If you have an Rh-negative blood type, you will receive an immunoglobulin injection at the time of the procedure to prevent the development of antibodies that could harm the fetus.
Some patients say they feel no pain during the amniocentesis, while others say they feel some pressure and cramping when the needle enters the uterus. After the procedure, you may experience cramping, spotting or leakage of amniotic fluid. We recommend you avoid lifting or standing on your feet for long periods of time for several hours following the procedure.
The amniotic fluid that is collected contains fetal cells. The cells are grown (cultured) in a laboratory for 10 to 12 days and then tested for genetic conditions and birth defects.
You will usually hear about your results from your health-care provider within a few weeks.
Serious risks associated with amniocentesis are rare and may include the following:
- A slight increase in the risk of miscarriage by 0.1 to 0.3%
- Within the first 12 hours after the procedure, a possibility of leaking amniotic fluid, spotting or cramping
- Rarely, the possibility of developing an infection
- A very small risk of an injury to the fetus.
Call your primary care provider or visit the nearest emergency room if you experience a fever, bleeding or persistent cramping after an amniocentesis.
While amniocentesis is a valuable diagnostic tool, it does not provide a complete picture of all the potential genetic conditions or birth defects that could affect the fetus. It primarily focuses on detecting certain genetic conditions.
In rare instances, amniocentesis may need to be repeated because we were not able to collect enough amniotic fluid or there were technical issues in the laboratory. This does not necessarily indicate a problem with the pregnancy.