Women's Health

Use of age as a threshold for recommending prenatal diagnosis is questioned

Age increases a woman's risk of having a child with a genetic disorder such as Down syndrome. Thus, physicians currently offer amniocentesis and chorionic villus sampling (CVS) for prenatal diagnosis of chromosomal disorders to women who will be at least 35 years of age at the time of delivery or who otherwise are at risk of giving birth to an infant with a genetic disorder.

The authors of a recent commentary call for eliminating strict age- or risk-based cutpoints for prenatal diagnosis in favor of the preferences of well-informed women. The original reasons for the age cutpoint are no longer relevant, explains lead author Miriam Kuppermann, Ph.D., M.P.H., of the Medical Effectiveness Research Center for Diverse Populations at the University of California, San Francisco. The research was supported in part by the Agency for Health Care Policy and Research (HS07373).

The authors note that a consensus panel recommended this cutpoint in 1979 in part because of limited prenatal screening resources. However, today there are 268 cytogenetic labs that can detect chromosomal abnormalities, and there are 500 board-certified cytogeneticists in the United States. Also, new data based on annual assessment (rather than the earlier 5-year assessment) of a woman's risk of giving birth to a child with Down syndrome show that the risk increases substantially among women in their early to mid-30s, but it does not spike suddenly at 35 years of age.

In addition, the age 35 cutoff was chosen because that is when the risk that a woman will have a miscarriage after the procedure is about equal to the probability that she is carrying a fetus affected by a chromosomal abnormality, assuming that women weigh these outcomes equally. However, data these authors collected on women's preferences showed that most women (83 percent) would prefer having a procedure-related miscarriage to giving birth to a child with Down syndrome. Finally, age 35 was chosen in 1979 because it was determined that was the age at which the procedure would be cost beneficial; i.e., the cost of providing amniocentesis to women 35 and over would be more than offset by the savings accrued in averting Down syndrome-affected births. This is a much more stringent economic requirement than is currently required of medical interventions, note the researchers.

See "Who should be offered prenatal diagnosis? The 35-year-old question," by Dr. Kuppermann, James D. Goldberg, M.D., Robert F. Nease, Jr., Ph.D., and A. Eugene Washington, M.D., M.Sc., in the February 1999 American Journal of Public Health 89(2), pp. 160-163.

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