ULTRASOUND-ADJUSTED RISK AND SPECTRUM OF FETAL CHROMOSOMAL ABNORMALITY IN WOMEN WITH ELEVATED MATERNAL SERUM ALPHA-FETOPROTEIN

Objective: To determine the incidence of chromosomal abnormality in so nographically normal fetuses after amniocentesis for elevated maternal serum alpha-fetoprotein (MSAFP), and to compare the spectrum of abnor mality with that seen in women undergoing amniocentesis for advanced m aternal age. Methods: Cytogenetic and sonographic findings from women undergoing amniocentesis for elevated MSAFP (at least 2.0 multiples of median) between 1988-1992 were reviewed retrospectively. The literatu re was reviewed and data compiled regarding the risk of chromosomal ab normality for women with elevated MSAFP levels. Results: The incidence of abnormal karyotype among all women with elevated MSAFP was 1.23% ( nine of 733). The risk of an abnormal karyotype with a normal ultrasou nd examination was 1.01% (seven of 696). This included three fetuses w ith sex chromosome abnormalities, three with de novo, apparently balan ced rearrangements, and one with an unbalanced structural rearrangemen t. Conclusions: The risk of chromosomal abnormality in nonselected pat ients, predominantly younger than 35 years of age, with elevated MSAFP and a sonographically normal fetus is 0.6%, based on a compilation of our data and reports published previously. The spectrum of abnormalit y in women with elevated MSAFP differs from that in women of advanced maternal age. Patients should be specifically counseled regarding this difference.