Suggestions for a One Age Screening Protocol

Since the 1970s, maternal age has been used as a screen for offering amniocentesis to pregnant women, with biochemical screening offered to younger women since the late 1980s.

However, there is debate about these guidelines (see, for example, Rosen, Kedar, Amiel, et al.; Haddow, Palomaki, Knight, et al.; Pauker and Pauker; Egan, Benn, Borgida, et al.; Dommergues, Audibert, Benattar, et al.). This controversy seems to be based largely on the trend toward women bearing children at later ages (from 1974 to 1997, the United States has seen a 2.7-fold increase in live births among women ages 35—49) (Egan, et al.). This age increase means a dramatic increase in the number of amniocenteses performed, with concomitant procedure-related losses and economic costs.

The most radical suggestion for changing the routine is to screen women of all ages in an identical manner (see last row of Table 1). The most promising of such approaches include ultrasound measurement of the thickness of subcutaneous edema in the neck of the fetus (fetal nuchal translucency) combined with new types of serum marker screening (e.g., PAPP-A). When these techniques are performed in the first trimester of pregnancy, and the results are combined with the risk based on maternal age alone, this regimen is believed to have an 80 to 90 percent detection rate for trisomy 21 and other chromosomal abnormalities (Nicolaides, Heath, and Liao). Although fetal nuchal trans-lucency screening has not been accepted as standard of care, the American College of Obstetrics and Gynecologists stated at the end of the twentieth century that it shows promise (1999).

The advantages of a single screening modality for women of all ages are that it would decrease the number of amniocenteses in older women and, with these more sensitive screening modalities, also increase the detection rate in younger women. (In terms of raw numbers, younger women have the greatest number of affected pregnancies.) Several sets of modeling data suggest that with this approach the overall detection rate would improve and the fetal loss rates would decrease (Rosen, Kedar, Amiel, et al.; Haddow, Palomaki, Knight, et al.; Dommergues, Audibert, Benattar, et al.). The disadvantage, however, would be that, since amniocentesis has a virtual 100 percent sensitivity, some fetuses with Down syndrome that would have been detected through universal screening of women over thirty-five would be missed, and some women over thirty-five would bear a child with Down syndrome who would not otherwise have done so. The ethical, and political, debates concern the fact that a medical service that was accepted as a right for pregnant women of a certain age would be withheld from those same women unless they had demonstrated risk. This may well appear to be an unacceptable form of sudden healthcare rationing to older pregnant women.

It is also worth noting that none of these one-age screening models refer to the detection of neural tube defects, but rather appear to exist in a separate universe of consideration and calculation. Thus, they would not solve the problem of multiple screenings and multiple chances for initial positive results and concomitant anxiety.

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