Amniotic fluid is the liquid that surrounds and protects a fetus during pregnancy. Amniotic fluid can be used for genetic testing in addition to other fetal health assessments, as it contains fetal cells with fetal DNA.

What is Amniocentesis?

Amniocentesis is a diagnostic procedure that uses a small amount of amniotic fluid to detect chromosomal abnormalities, some inherited disorders, evaluates for congenital infections and can help with diagnosis of neural tube defects/spina bifida. It can be performed after 16 weeks, during the second or third trimesters of a pregnancy.

What are the Benefits and Risks of Amniocentesis?

Amniocentesis can provide early diagnosis of genetic conditions, so that you can make healthcare decisions sooner.

Risks of the procedure include:

  • Miscarriage: There is a small risk of miscarriage (<1%)
  • Infection: There is a risk of infection in the uterus or amniotic sac, though this is rare.
  • Injury to the fetus: Rarely, the needle used for amniocentesis can cause injury to the fetus.
  • Leaking Amniotic Fluid: A small amount of fluid may leak from the uterus after the procedure; this usually resolves on its own. Persistent leakage of fluid may occur in very rare cases and can lead to pregnancy loss.

Why Is Amniocentesis Performed?

Amniocentesis can aid in the diagnosis of chromosomal conditions such as Down syndrome, other genetic conditions such as cystic fibrosis, sickle cell disease, and Tay-Sachs disease, or neural tube defects. It can also be used to evaluate fetal lung maturation/development. It is very accurate.

Who Should Consider Amniocentesis?

According to the American College of Obstetricians and Gynecologists (ACOG), all pregnant women should be offered the option to have a diagnostic testing, such as amniocentesis. 

It is typically recommended if you are at risk of having a baby with a genetic condition or if there are concerns based on ultrasound or other prenatal test findings.

Risk factors include:

  • You are 35 years or older
  • You or your partner have a family history of genetic conditions
  • Child affected by a genetic condition
  • Screening tests (such as NIPT) or carrier screening indicate increased risk of a genetic condition in the fetus
  • Ultrasound evaluation is concerning for fetal anomalies or evidence of congenital infection

When Is Amniocentesis Performed During Pregnancy?

Amniocentesis is a diagnostic procedure typically performed in the second and third trimesters of pregnancy, as early as at 16 weeks of pregnancy by a maternal-fetal medicine (MFM) specialist.

The Amniocentesis Procedure

Amniocentesis involves inserting a thin needle through the woman’s abdomen, guided by ultrasound, to collect a sample of amniotic fluid. The amniotic fluid contains fetal cells, which are then sent to a laboratory for analysis.

The entire procedure may take approximately 30 minutes, but the actual sampling process takes just a minute or two. Following the sampling, fetal heart rate is monitored by ultrasound.

Understanding the Results of Amniocentesis

The collected cells may be cultured for up to 14 days or analyzed directly. Preliminary results (known as FISH analysis) on chromosomes 13, 18, 21, and sex chromosomes, are often available within 72 hours. 

Your genetic counselor or maternal fetal medicine physician will follow up with you to discuss test results and any follow-up testing that is recommended.

Amniocentesis vs. Chorionic Villus Sampling (CVS)

Chorionic villus sampling (CVS) is a diagnostic test that is typically performed between 12-13 weeks of pregnancy. It involves collecting a small sample of cells from the placenta, which are then sent to a laboratory for analysis. It can be obtained either transvaginally through the cervix or through the abdominal wall, depending on various factors.

While amniocentesis is performed later in a pregnancy than CVS, unlike CVS, it is able to evaluate risk of neural tube defects and assess for risk of congenital infections, if indicated. It can also be used to assess fetal lung development.

Your maternal-fetal medicine specialist can discuss the risks and benefits of each procedure to help you determine which may be best for your clinical situation.

Book An Appointment!

If you have been referred by your primary care provider, OB-GYN or other healthcare provider, please call our office to schedule an appointment. Our dedicated team will help you understand what information to provide in advance to ensure you see the care best suited to your condition.

Please find the patient information form for Amniocentesis here.