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Who is a candidate for amniocentesis?
Women over the age of 35 have an increased chance of having a baby with chromosomal abnormalities. Therefore, the current recommendation is that women who will be age 35 or older at the time of delivery be offered a genetic amniocentesis for the testing of fetal chromosomes. Chromosomal abnormalities in the fetus can lead to intellectual disabilities or other birth defects, as seen with Down's syndrome. The possibility of having a baby with a chromosomal defect increases with the age of the mother.
- At age 35, the chance is about 1 in 178.
- By age 40, the rate increases to 1 in 63.
- By age 48, the ratio is 1 in 8.
- For women younger than 35, the risk of complications as a result of amniocentesis outweighs the possibility that the baby has a chromosomal abnormality (see below, "Is Amniocentesis Safe?").
- After 35, the chance of delivering a baby with a chromosomal abnormality may be more common than experiencing the complications associated with this procedure.
If there is a family history of chromosomal problems or history of prior births in which a chromosomal defect was identified, amniocentesis may be recommended. However, the exact benefit of amniocentesis in these situations is uncertain. Many chromosomal defects may not reappear in subsequent pregnancies, and genetic counseling can help a woman decide whether amniocentesis would be of value in these situations.