What Is Amniocentesis?

If you are pregnant and at increased risk for certain genetic conditions, testing is available for you and your baby to help increase the likelihood of positive outcomes. One of these tests is called an amniocentesis.

What Is an Amniocentesis Test?

As your baby grows over the nine months of your pregnancy, they are surrounded by a cushion of liquid known as amniotic fluid. This fluid not only protects your baby, it also regulates their temperature and allows them to have room to move and develop properly. The amniotic fluid contains enzymes, proteins and hormones that work together to support your baby’s development. 

During an amniocentesis, the doctor uses a needle to remove some of the amniotic fluid from the womb for testing. An amniocentesis can be used for a variety of purposes, including:

• Genetic testing: The amniotic fluid contains cells that are shed by the fetus. These cells are full of genetic information that can help doctors diagnose genetic disorders such as spina bifida or Down syndrome.
• Fetal lung testing: Doctors can test the amniotic fluid to make sure a baby’s lungs are mature enough for birth.
• Diagnosis of fetal infections: An amniocentesis can help doctors identify infections or illnesses, including anemia, in developing babies.
• Treatment for polyhydramnios: Polyhydramnios — the accumulation of too much amniotic fluid in the uterus — can be treated with an amniocentesis. The doctor uses the procedure to drain off excess fluid.
• Paternity testing: The cells collected from the amniotic fluid can be compared to the DNA of the potential father.

Amniocentesis for Genetic Testing

Due to its accuracy, an amniocentesis is often used to diagnose potential genetic diseases. This test is performed between the 15th and 20th weeks of pregnancy and is often prompted by the results of testing completed earlier in the pregnancy. Some risk factors that may lead you to choose an amniocentesis include:

• Family history of or a previous child with a genetic disorder such as Down syndrome or cystic fibrosis
• Risk of spina bifida or other open neural tube defects
• Maternal age of 35 or over
• Abnormal maternal screening or ultrasound tests

During an amniocentesis, you and your baby’s vitals will be monitored as the doctor guides a thin, hollow needle through your abdomen and into the uterus to collect a small amount of amniotic fluid. This fluid is then sent to a lab for testing. After the test, you may be advised to avoid strenuous activity and rest for 24 hours.

Amniocentesis tests are not recommended before the 15th week of pregnancy due to the increased risk of miscarriage. When completed during the second trimester, there is a less than 1% risk of miscarriage. Some other complications may include:

• Cramping
• Bleeding
• Infection
• Preterm labor

If you experience fever, chills, severe belly pain/cramping or a change in your baby’s movement, you should reach out to your healthcare provider immediately.

Having an amniocentesis done is your choice; it is not a required test, even if you’re at risk for a genetic disorder. It’s important to speak with your doctor about the risks and any concerns or questions you may have. A genetic counselor can help you assess your risks and understand how genetic disorders may affect your health or your baby’s health. Working with a maternal-fetal medicine specialist can provide you with the most well-rounded picture of what an amniocentesis means for your pregnancy.

Results of an Amniocentesis for Genetic Disorders

If you choose to have an amniocentesis and receive a diagnosis of a genetic disorder or birth defect, it’s important to be prepared for the emotions that you may experience. Disappointment, anxiety or guilt are all common reactions to a genetic disorder diagnosis, but you should never feel like you have to handle the news alone. A strong support structure of friends, family and healthcare providers can help you locate resources and plan for the future. Many practices have specialists on staff who can help you learn more and make decisions about next steps as you prepare for your baby’s arrival. Regardless of the diagnosis, please keep in mind that you are not alone.

Like other diagnostic tests, an amniocentesis can help your doctors effectively identify potential issues early enough that intervention and treatment may be possible. By providing a comprehensive look at your baby’s health, these tests create an accurate and detailed picture that is used to increase the likelihood of positive outcomes. While some disorders can be treated with surgery while the baby is still in the womb, others will need to be addressed after your baby has been born. There are many resources available today to support you and your baby through your pregnancy to delivery and beyond.

High-Risk Pregnancies

There are a wide variety of reasons that a pregnancy might be considered high-risk, including maternal age, previous medical history and complications that occur during the pregnancy. If you are at high-risk or your pregnancy becomes high-risk, you can work with a maternal-fetal medicine specialist to support you and help increase the likelihood of positive outcomes. A maternal-fetal medicine specialist often works with an experienced team of healthcare professionals, including genetic counselors and fetal cardiologists, to address issues that you or your baby may be facing. Together, these medical experts can map out a plan to support your baby with testing, monitoring, treatments and sometimes surgery, with the goal of having you and your baby at home and healthy after delivery.