Amniocentesis

Amniocentesis is done to remove amniotic fluid and cells from the uterus for testing or treatment. Amniotic fluid surrounds and protects a baby during pregnancy. Amniocentesis can provide useful information about a baby's health. But it's important to know the risks of amniocentesis — and be prepared for the results.

Amniocentesis can be done for a number of reasons: Genetic testing. Genetic amniocentesis involves taking a sample of amniotic fluid and testing the DNA from the cells for diagnosis of certain conditions, such as Down syndrome. This might follow another screening test that showed a high risk of the condition. Diagnosis of fetal infection. Occasionally, amniocentesis is used to look for infection or other illness in the baby. Treatment. Amniocentesis might be done to drain amniotic fluid from the uterus if too much has built up — a condition called polyhydramnios. Fetal lung testing. If delivery is planned sooner than 39 weeks, amniotic fluid might be tested to help find out whether a baby's lungs are mature enough for birth. This is rarely done.

Amniocentesis carries risks, which occur in approximately 1 in 900 tests. They include: Leaking amniotic fluid. Rarely, amniotic fluid leaks through the vagina after amniocentesis. In most cases, the amount of fluid lost is small and stops within one week with no effect on the pregnancy. Miscarriage. Second-trimester amniocentesis carries a slight risk of miscarriage — about 0.1% to 0.3% when done by a skilled person using ultrasound. Research suggests that the risk of pregnancy loss is higher for amniocentesis done before 15 weeks of pregnancy. Needle injury. During amniocentesis, the baby might move an arm or leg into the path of the needle. Serious needle injuries are rare. Rh sensitization. Rarely, amniocentesis might cause the baby's blood cells to enter the pregnant person's bloodstream. Those with Rh negative blood who haven't developed antibodies to Rh positive blood are given an injection of a blood product, Rh immune globulin, after amniocentesis. This prevents the body from making Rh antibodies that can cross the placenta and damage the baby's red blood cells. Infection. Very rarely, amniocentesis might trigger a uterine infection. Infection transmission. Someone who has an infection — such as hepatitis C, toxoplasmosis or HIV / AIDS — might transfer it to the baby during amniocentesis. Remember, genetic amniocentesis is usually offered to pregnant people for whom the test results might greatly affect how they manage the pregnancy. The decision to have genetic amniocentesis is yours. Your health care provider or genetic counselor can give you information to help you decide.

Your health care provider will explain the procedure and ask you to sign a consent form. Consider asking someone to accompany you to the appointment for emotional support or to drive you home afterward.

Amniocentesis is usually done in an outpatient obstetric center or a health care provider's office.