Aneuploidy: is cytogenetic evaluation indicated for unexplained elevated maternal serum alpha-fetoprotein?
OBJECTIVE: The purpose of this study was to examine the value of fetal karyotyping in pregnancies complicated by unexplained elevated maternal serum alpha-fetoprotein. METHODS: 58,162 obstetrical ultrasounds performed at Indiana University Prenatal Diagnostic Center from July 1988 to March 1996 for various indications were reviewed using a computerized database. Fetuses with maternal serum alpha-fetoprotein MOM >2.5 and normal extensive ultrasounds were identified. Maternal demographic data and fetal karyotype were obtained. Statistical analysis was performed using the Chi square test. RESULTS: 790 patients received ultrasounds for evaluation of elevated maternal serum alpha-fetoprotein. Of the 595 patients with normal scans, 189 (31.8%) underwent amniocentesis and cytogenetic evaluation. Two chromosomal abnormalities were detected (1.1%) including an inversion in the long arm of the number 9 chromosome and a balanced translocation, 46XX,t(7;8),(q34;q23.1). This was not statistically significant (p = 0.317) compared to the theoretical risk of chromosomal anomalies in this sample population based solely on maternal age (0.3%). CONCLUSION: The prevalence of karyotypic abnormalities in our patients with unexplained elevated maternal serum alpha-fetoprotein values and a normal targeted ultrasound examination was not significantly elevated. Of the abnormalities detected, none were life threatening or associated with significant perinatal morbidity. Our results suggest that routine karyotype analysis in this group of patients is of limited value.