Amniocentesis is a prenatal test used to help diagnose genetic diseases and disorders during pregnancy. However, there are a number of amniocentesis risks that parents need to be aware of before taking the preventative test. For one, the amnio test is expensive, invasive, and can raise the risk of miscarriage. There are newer, lower-cost alternatives to the amniocentesis test that are lower risk as well. And yet amniocentesis remains the most comprehensive way to reassure moms and dads that their baby is healthy. So, this test understandably raises a number of difficult questions.
What Is Amniocentesis?
Amniocentesis is essentially an amniotic fluid test that’s taken by inserting a long needle into a pregnant woman’s womb. It sounds primitive, outdated, and harsh, but it’s still traditionally thought of as the gold standard for prenatal genetic diagnostic testing.
“The baby is essentially taking a bath in their amniotic fluid,” says Erin O’Toole, a prenatal genetic counselor. “Just like how we shed our skin cells into our bathwater, the baby does the same thing in its amniotic fluid. By sampling the amniotic fluid, we can get cells from the baby’s skin and some other organs to use for genetic testing.”
The most common reason for an amniocentesis test is to check for a genetic condition in pregnancy. Some people have specific concerns due to their family history or maternal age; others simply would like to be as prepared as they can since genetic conditions can cause complications in pregnancy or birth, as well as congenital problems in babies, both physical and developmental.
“Testing options for genetic conditions in pregnancy can be split into two categories: screening tests that have no risk, but cannot give definite yes or no answers; and diagnostic tests that can have risks associated but can give definitive yes or no answers,” says O’Toole. “In the past, it was very common for a pregnant woman to simply decide to have amniocentesis in her pregnancy. But today, the improved accuracy of screening options has limited the number of people that elect amniocentesis in their pregnancies – more are electing to start with screening tests like blood work or ultrasound and only move to amniocentesis if a concern is detected.”
What Are the Biggest Amniocentesis Risks?
Any procedure that involves inserting a needle into an organ has risks, although generally, these risks are rare. “The most recent data showed an approximately 1 in 900 chance for a miscarriage to occur as a result of an amniocentesis,” cautions O’Toole. “Once the pregnancy has reached viability outside the womb, this becomes a risk of preterm delivery. Older studies quote a 1 in 300 risk for an adverse outcome and some more conservative offices still quote this number.”
- Amniocentesis is invasive – amniocentesis involves passing a very long needle into the womb, guided by ultrasound imaging, where it can extract a small amount of amniotic fluid for testing.
- Amniocentesis can lead to miscarriage – it’s a more comprehensive test, but it has a cost. Current research shows a 1:900 chance for miscarriage or preterm delivery with amniocentesis.
- Amniocentesis is not a guarantee – although amniocentesis allows doctors to test for a wide variety of conditions, no amount of genetic testing can rule out everything.
How Is an Amniocentesis Performed?
Amniocentesis is not done blindly; the team uses ultrasound in order to find the biggest pocket of amniotic fluid and monitor the baby. As described, a long, thin needle is inserted through the abdomen into the womb, where it can draw up to 20 mL of amniotic fluid. The length of the needle can be intimidating, certainly, but that doesn’t necessarily mean it will be miserable for the mother, according to O’Toole.
“Most mothers describe that when the needle goes into their skin it feels just like a blood draw,” she explains. “When the needle goes into the uterus there is normally some mild cramping. The whole procedure lasts 1 to 2 minutes. Some patients do not think it’s bad at all, but others find it pretty uncomfortable.”
When Can Amniocentesis Be Performed?
An amnio can be performed by week 15 of gestation, although some physicians wait until 16 weeks. It is usually performed before week 21, although in the case of an early delivery – often considered for the health of the mother or child – determining fetal lung maturity requires amnio later in the pregnancy.