TRIPLOID PARTIAL MOLAR PREGNANCY DETECTED THROUGH MATERNAL SERUM ALPHA-FETOPROTEIN AND HCG SCREENING

Background: Screening for Down syndrome using maternal serum alpha-fet oprotein (MSAFP) and hCG, with or without unconjugated estriol (E3), h as become Standard practice in much of the United States. When both MS AFP and hCG are elevated, the possibility of a partial molar pregnancy with fetal neural tube or abdominal-wall defect should be added to th e differential diagnosis, as illustrated by this case. Case: A 22-year -old woman had elevated MSAFP and hCG levels on routine screening at 1 6 weeks' gestation. Ultrasound examination suggested a neural tube def ect and a thickened placenta, Amniocentesis was performed. She very ra pidly developed preeclampsia. Fluorescence in situ hybridization showe d three distinct spots for the three probes tested. A triploid karyoty pe was confirmed with standard cytogenetic analysis. The fetus had an open neural tube defect, and placental pathology was consistent with a partial hydatidiform mole. Conclusions: A possible partial molar preg nancy with abdominal-wall or open neural tube defect should be added t o the differential diagnosis for interpreting Down syndrome screens wh en both MSAFP and hCG are elevated. A presumptive diagnosis of triploi dy using fluorescence in situ hybridization was important in the manag ement of this pregnancy.