A procedure whereby a needle is introduced through the abdominal wall and into the pregnant uterus to obtain amniotic fluid. The procedure is most commonly used to obtain fetal cells present in the fluid to examine the fetal chromosomes or occasionally fetal DNA. Biochemical tests may be performed on cultured cells or the fluid itself. The procedure is usually carried out at 16 weeks gestation.
Depending on the nature of the laboratory test undertaken on the sample, the result may not be available for several weeks.
When a chromosomal, DNA or biochemical test is available for a known genetic disorder, many families prefer the sample to be taken much earlier in pregnancy, by chorionic villus sampling at ten weeks.
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