MATERNAL SERUM ALPHA-FETOPROTEIN SCREENING FOR CHROMOSOMAL-ABNORMALITIES - A PROSPECTIVE-STUDY IN WOMEN AGED 35 AND OLDER

OBJECTIVE: Our purpose was to determine the detection and false-positi ve rates for maternal serum alpha-fetoprotein measurement to screen fo r fetal Down syndrome and other chromosomal abnormalities in women gre ater than or equal to 35 years old. STUDY DESIGN: A total of 3896 wome n had serum maternal serum alpha-fetoprotein levels measured routinely before amniocentesis for the indication of advanced maternal age. RES ULTS: Eighty-five percent (28/33) of fetal Down syndrome pregnancies h ad second-trimester risks of greater than or equal to 1:270 on the bas is of a combination of maternal serum alpha-fetoprotein measurement an d maternal age. Risks were also greater than or equal to 1:270 in 63% of the unaffected pregnancies. Sex chromosome aneuploidies, translocat ions, and other nonautosomal chromosome abnormalities in this study po pulation were not associated with altered maternal serum alpha-fetopro tein levels; 51.9% (14/27) of these, however, were also assigned risks of greater than or equal to 1:270. CONCLUSIONS: Maternal serum alpha- fetoprotein screening is more accurate than age alone for assigning in dividual Down syndrome risk in pregnant women greater than or equal to 35 years old. Counseling for women in this age group should include i nformation regarding the lower sensitivity of maternal serum alpha-fet oprotein screening for detecting fetal Down syndrome and other chromos omal abnormalities (especially sex chromosome aneuploidies) compared w ith offering amniocentesis to these women.