Amniocentesis

Pregnant women over the age of 35 years are candidates for amniocentesis. This procedure may be performed for chromosome analysis or the detection of genetic defects and conditions in the fetus. It can also be used to determine the maturity of the fetal lungs or the cause of a fever in the mother.

In the case of polyhydramnios, amniocentesis might be done to drain excess amniotic fluid from your uterus in this case serving a therapeutic purpose. It also can be used to collect DNA from the fetus that can then be compared to DNA from the potential father.

Amniocentesis carries various risks, including:

• Leaking amniotic fluid: Rarely small amounts of fluid leaks through your front passage following amniocentesis. In most cases, the amount of fluid lost is small and stops within a week and the pregnancy is likely to continue normally.
• Miscarriage: The risk of pregnancy loss is higher for amniocentesis done before 15 weeks of pregnancy. Second-trimester amniocentesis carries a slight risk of miscarriage about 0.1-0.3%.
• Needle injury: The fetus may be injured during this procedure as the fetus may move an arm or a leg into the path of the needle.
• Infection: Amniocentesis might trigger a uterine infection though very rarely.
• Infection transmission: If you have an infection such as hepatitis C, HIV/AIDS or toxoplasmosis might be transferred to the baby during this procedure.
• Rh sensitization: This procedure might cause the baby’s blood cells to enter the mother’s bloodstream though this is rare. If you have Rh-negative blood and you have not developed antibodies to Rh-positive blood, you will be given an injection of a blood product called Rh immune globulin after amniocentesis. This will prevent your body from producing Rh antibodies that can cross the placenta and damage your baby’s red blood cells. A blood test can detect if you have begun to produce antibodies.

How you prepare

Your doctor will explain the procedure and ask you to give consent before it begins.

If you are having amniocentesis done before week 20 of pregnancy, it might be helpful to have your bladder full during the procedure to support the uterus. Drink plenty of fluids before your appointment.

After 20 weeks of pregnancy, your bladder should be empty during the procedure to reduce the risk of puncture.

Consider asking someone to accompany you to the appointment for emotional support or to drive you home afterwards.

What you can expect

Amniocentesis is done usually in an outpatient obstetric facility.

Before the procedure

Before the procedure, your doctor may order some tests. An obstetric scan may be necessary to show the size of the uterus and the wellbeing of the fetus.

During the procedure

Your doctor will ask you to lie still and on your back on an exam table and expose your abdomen. A gel will be applied to your abdomen and then use a small device known as an ultrasound transducer to show your baby’s position on a monitor.

Then an antiseptic will be used to clean the abdomen. Guided by ultrasound your doctor inserts a thin hollow needle through the wall of your abdomen into the uterus. A small amount of amniotic fluid is drawn into a syringe and the needle removed. The amount of fluid drawn depends on the number of weeks the pregnancy has progressed.

A stinging sensation will be felt when the needle enters your skin, and you might feel cramping when the needle enters your uterus.

After the procedure

The sample of amniotic fluid taken will be sent to the laboratory for analysis. Some results will be available in a few days and others may take up to four weeks. After the procedure, your baby’s heart rate will still be monitored using the ultrasound.

Cramping and mild discomfort might be experienced after amniocentesis however there are certain alarm signs for which you should contact your health care provider:

• Fever
• Redness and inflammation at the injection site
• Uterine cramping that is severe and lasts more than a few hours
• Unusual fetal activity or a lack of fetal movement
• Loss of or vaginal bleeding or loss of amniotic fluid through the vagina.

Your doctor or genetic counsellor will help you understand the results of the test. Test results can reliably rule out or diagnose various genetic conditions such as Down syndrome. However not all genetic conditions can be identified with this test. If your test indicates your baby has a chromosomal or genetic condition that cannot be treated, you might be faced with heart wrenching decisions- such as whether to continue the pregnancy. Seek support from your health care team and your loved ones.

For fetal lung maturity amniocentesis, test results can reliably indicate a baby’s lung maturity. If you need to deliver the baby early, this information can offer reassurance that your baby is ready for birth.