So when Sarah was 16 weeks pregnant, she got an amniocentesis.
amniocentesis am·ni·o·cen·te·sis (ām'nē-ō-sěn-tē'sĭs)
n. pl. am·ni·o·cen·te·ses (-sēz')
A procedure in which a small sample of amniotic fluid is drawn out of the uterus through a needle inserted in the abdomen and is then analyzed to detect genetic abnormalities in the fetus or to determine the sex of the fetus.
A procedure usually done about the sixteenth week of pregnancy in which a small sample of amniotic fluid is drawn out of the uterus through a needle inserted in the abdomen. The fluid is analyzed to determine the gender of the fetus or the presence of genetic abnormalities.
A procedure for finding certain disorders in a fetus during pregnancy. In amniocentesis, a small amount of the salty liquid that surrounds the fetus in the amniotic sac is drawn out through a needle inserted into the mother's abdomen. The fluid generally contains some isolated cells from the fetus. These cells are analyzed to detect abnormalities in the chromosomes of the fetus, such as Down's syndrome, and may also be used to judge some other conditions, such as the maturity of the fetus's lungs.