What is an amniocentesis?
Amniocentesis is a test to look at the fluid that surrounds your baby (fetus) in the uterus. Amniotic fluid has cells and other substances that can give clues about the health of your fetus.
For this test, a needle is put gently through your belly into your uterus. About 2 Tbsp (30 mL) of fluid is taken out and looked at.
This test may be done between weeks 15 and 20 to look at the baby’s genes. It can also be used later in pregnancy.
Amniocentesis for Genetic Testing
Amniocentesis is often done around week 16 to see if a fetus has certain genetic conditions. It can also tell the sex of a fetus and help find certain neural tube defects.
Amniotic fluid has cells that have been shed by your growing fetus. The cells are checked for the number and size of chromosomes. This can show if there are any problems that put the baby at risk for certain conditions, such as Down syndrome. But this test can’t find many common birth defects, such as cleft lip, cleft palate, or heart problems.
Testing is most often done as soon as possible so women and their families have time to think about their options.
Amniocentesis in Late Pregnancy
if your doctor thinks you could have an infection of the amniotic fluid (chorioamnionitis), your doctor may recommend this test be done later in pregnancy.