Objective: The purpose of this study was to examine fetal chromosomal abnormalities in pregnancies complicated by unexplained elevated maternal serum alpha-fetoprotein (MSAFP).
Study design: We reviewed, using a computerized database, 58,162 obstetrical ultrasounds that were performed for various indications. Fetuses with MSAFP multiples of the median (MOM) > or = 2.5 and normal extensive ultrasounds were identified. Maternal demographic data and fetal karyotype were obtained.
Results: Seven hundred eighty-nine patients received ultrasounds for evaluation of elevated MSAFP. Of the 595 patients with normal scans, 195 (32.8%) underwent amniocentesis and cytogenetic evaluation. Two chromosomal abnormalities were detected (1.0%), including an inversion and a balanced translocation.
Conclusion: The two karyotypic abnormalities identified in our study consisted of structural rearrangements. Patients undergoing karyotype analysis for unexplained elevated MSAFP should be counseled that the types of aneuploidy detected under this circumstance differ from those associated with advanced age and specific fetal anomalies (trisomy and triploidy).