Recognition of Smith-Lemli-Opitz syndrome (RSH) in the fetus: Utility of ultrasonography and biochemical analysis in pregnancies with low maternal serum estriol

Smith-Lemli-Opitz syndrome (SLOS), or RSH, is an autosomal recessive disorder caused by mutations of the gene encoding 7-dehydrocholesterol reductase (DHCR7). The utility of maternal serum screens and ultrasound as prenatal screening methods for SLOS is presently undetermined. We report the clinical, cytogenetic, biochemical, and molecular findings of a stillborn with SLOS. The diagnosis was made postnatally on the basis of physical findings and confirmed by biochemical and DNA analyses of fetal tissue. Although abnormalities were detected by maternal serum triple screen and prenatal ultrasonography, a diagnosis of SLOS was not suspected before delivery. This study demonstrates that patients with SLOS may escape prenatal diagnosis despite the presence of multiple anomalies and abnormal maternal serum screen results, and lends support for consideration of prenatal biochemical testing for SLOS in pregnancies with these findings. As SLOS is a severe autosomal recessive disorder with a recurrence risk of 25%, ultrasonographic, cytogenetic, and biochemical analyses in the second trimester should be considered if abnormal maternal serum screening results, specifically low levels of unconjugated estriol, are detected.