Elevated maternal serum alpha-fetoprotein levels: what is the risk of fetal aneuploidy?

Objective: Our purpose was to present the findings of a project to determine the efficacy of including routine fetal karyotyping in the investigation of an elevated maternal serum alpha-fetoprotein concentration.

Study Design: Targeted ultrasonographic examinations were performed in 658 patients with elevated maternal serum alpha-fetoprotein levels. The scans were normal in 557 women, of whom 427 consented to amniocentesis; 435 fetuses were karyotyped. In the 101 patients with abnormal ultrasonographic examinations 75 had fetal karyotyping.

Results: In the 435 fetuses with normal scans, two had karyotypic anomalies, a 47,XYY and an inherited balanced translocation. Three fetuses with normal karyotypes and high amniotic fluid alpha-fetoprotein levels had congenital nephrosis. In the 101 patients with abnormal scans, 75 fetuses were karyotyped. There were four aneuploidies. Among the 26 patients with abnormal scans who declined amniocentesis one fetus with multiple anomalies was karyotyped after delivery and triploidy was discovered.

Conclusions: These results provide little justification for including fetal karyotyping in the investigation of elevated maternal serum alpha-fetoprotein when the targeted ultrasonographic examination is normal. When it is abnormal, selective rather than routine karyotyping is more appropriate.