Amniocentesis

Results

Amniocentesis is a test to look at the fluid (amniotic fluid) that surrounds your baby (fetus).

• Cells from your fetus are looked at carefully for the proper number and arrangement of the cell parts (chromosomes) that show genetic disease. Normally there are 46 chromosomes in each cell, arranged in 23 pairs. Chromosomes also tell the sex of your fetus. It takes about 2 weeks to get the results.
• The amounts of some substances in the amniotic fluid may be measured. These results can find some birth defects, more than 100 genetic diseases, and the maturity of your fetus. Some of the tests are done only for women with high-risk pregnancies. Results generally are ready in about two weeks.
  • The amounts of alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) are measured early in the pregnancy to look for neural tube defects.
  • The amounts of phosphatidyl glycerol and phosphatidyl inositol, and the lecithin/sphingomyelin (L/S) ratio, are measured later in pregnancy to estimate your fetus's age and how mature the lungs are. This is done when you may need to deliver early.
  • The amount of bilirubin is measured to see whether your fetus is being harmed by your immune system. This can happen if Rh sensitization has occurred.
  • The presence of meconium can mean that your fetus is in distress.
  • Cells in the amniotic fluid can be counted and checked for an infection (chorioamnionitis). If chorioamnionitis is present, a culture of the amniotic fluid can be done to see what type of organism is causing the infection.

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Author:	Jan Nissl, RN, BS	Last Updated May 29, 2006
Medical Review:	Renée M. Crichlow, MD - Family Medicine Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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