Amniocentesis

Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation. In this procedure, a thin needle is inserted into the abdomen of the pregnant woman. The needle punctures the amnion, which is the membrane that surrounds the developing fetus. The fluid within the amnion is called amniotic fluid, and because this fluid surrounds the developing fetus, it contains fetal cells. The amniotic fluid is sampled and analyzed via methods such as karyotyping and DNA analysis technology for genetic abnormalities. An amniocentesis is typically performed in the second trimester between the 15th and 20th week of gestation. Women who choose to have this test are primarily those at increased risk for genetic and chromosomal problems, in part because the test is invasive and carries a small risk of pregnancy loss. However, the American College of Obstetricians and Gynecologists recommends that all women be offered prenatal assessment for aneuploidy, or the presence of an abnormal number of chromosomes, by either genetic screening or diagnostic testing independent of maternal age or risk factors. There are relative contraindications to performing an amniocentesis, however no absolute contraindications have been identified. Physicians have used the process of inserting a needle transabdominal into the uterus to extract amniotic fluid for the management of hydramnios, or excess amniotic fluid, as early as the late 1800s.