What is an amniocentesis and why is it done ?

Amniocentesis is a procedure in which amniotic fluid is removed from the uterus for testing or treatment. Amniotic fluid is the fluid that surrounds and protects a baby during pregnancy. This fluid contains fetal cells and chemicals produced by the developing baby. An Amniocentesis is typically done to determine if a baby has a genetic abnormality, an infection or to determine definitively the baby’s gestational age. An amniocentesis is usually performed between 14-16 weeks gestation.

Who is recommended for an amniocentesis?

Women at an increased risk for genetic abnormalities are recommended to have amniocentesis.

How is an Amniocentesis Performed?

An amniocentesis is typically done as an outpatient procedure. Some Obstetricians have facilities to do them in their offices, but more than likely an amniocentesis is done in an outpatient hospital/surgical facility. A full bladder is necessary for the procedure, but you need not be fasting. During the procedure you will lay on an examining table with your belly exposed. First the doctor will do an ultrasound to determine the location of the baby and to locate a sampling area away from the baby.  After cleansing your abdomen with sterile solution, the doctor will insert a needle through the abdominal wall into the sampling area and will withdraw amniotic fluid for testing. Once the fluid is withdrawn, it is sent to the lab for testing. The entire procedure is relatively brief, an hour or less. The actual fluid draw is only moments and the bulk of the time is spent doing the ultrasound and monitoring the baby.

What You May Experience During and Just after the Procedure

Most women note some stinging as the needle is inserted and some pressure. Following the procedure there may be some uterine cramping and occasionally some women experience some fluid leakage from the sampling site. This is usually very brief and stops spontaneously. If any of these symptoms don’t subside, contact your obstetrician immediately.

Potential Complications

An amniocentesis is not without risk. However, in cases where it is recommended, the risks are believed to outweigh than not having the procedure.

  • Miscarriage. Early amniocentesis carries a slight risk of miscarriage, often due to rupture of the amniotic sac. The risk of miscarriage is highest when the procedure is done early in pregnancy, before the two layers of fetal membranes have sealed.
  • Cramping and vaginal bleeding.
  • Needle injury at the site where the fluid is withdrawn.
  • Leaking amniotic fluid. Rarely, amniotic fluid leaks through the vagina after amniocentesis. If the leak seals, the pregnancy may proceed normally. Sometimes, however, the leakage leads to orthopedic problems for the baby in early infancy and childhood.
  • Rh sensitization.
  • Infection

The purpose of having an amniocentesis is to determine if there is a genetic and/or developmental defect in the baby. However, an amniocentesis is not a curative or therapeutic test. Once an amniocentesis is performed, parents have to decide with their obstetrician and any other health care professionals the next step to take.