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Original Article
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Volume 330:1114-1118 April 21, 1994 Number 16
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Reducing the Need for Amniocentesis in Women 35 Years of Age or Older with Serum Markers for Screening
James E. Haddow, Glenn E. Palomaki, George J. Knight, George C. Cunningham, Linda S. Lustig, and Patricia A. Boyd

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ABSTRACT

Background As maternal age advances, the risk of fetal Down's syndrome increases. Pregnant women 35 years of age or older are routinely offered amniocentesis because of this risk. Recently, maternal serum markers have been reported to be useful in screening for Down's syndrome, primarily in younger women. We therefore investigated whether offering amniocentesis only to selected women 35 years of age or older who were identified by screening measurements in serum might prove a useful alternative to the current practice.

Methods We studied 5385 women with singleton pregnancies who were 35 years of age or older and were undergoing routine amniocentesis. Along with information about the pregnancy, we obtained a serum sample for measurement of alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin. Individual estimates of the risk of Down's syndrome in the fetus were calculated for each pregnancy before the karyotype was known.

Results If amniocentesis had been reserved for the women calculated to have a risk greater than 1 in 200 of having a fetus with Down's syndrome, 48 of the 54 cases of Down's syndrome (89 percent) would have been identified; 25 percent of the unaffected pregnancies would also have been identified as being at high risk for Down's syndrome (false positives). Seven of 15 fetuses (47 percent) with other trisomies, 11 of 25 (44 percent) with sex aneuploidy, and 1 of 9 (11 percent) with miscellaneous chromosomal abnormalities would also have been detected. In practice, such screening would have made 75 percent of the amniocenteses unnecessary, along with a proportion of the amniocentesis-associated fetal losses. If the cutoff for the risk of Down's syndrome were set higher than 1 in 200, both the rate of detection and the false positive rate would be lower. Conversely, these rates would be higher if the cutoff were set lower.

Conclusions Prenatal screening of serum to generate individual estimates of the risk of Down's syndrome in the fetus can provide a basis for decision making in the cases of women 35 years of age or older, as it does in younger pregnant women, and is an alternative to current testing practices. .


Source Information

From the Foundation for Blood Research, Scarborough, Me. (J.E.H., G.E.P., G.J.K.); the California Department of Health Services, Genetic Disease Branch, Berkeley (G.C.C., L.S.L.); and the California Public Health Foundation, Berkeley (P.A.B.).

Address reprint requests to Dr. Haddow at the Foundation for Blood Research, Scarborough, ME 04074.

Full Text of this Article


Related Letters:

Triple-Marker Screening of Serum for Down's Syndrome
Herrmann J., Haddow J. E., Palomaki G. E.
Extract | Full Text  
N Engl J Med 1994; 331:681-682, Sep 8, 1994. Correspondence

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