Maternal urinary beta-core hCG in chromosomally abnormal pregnancies in the first trimester

We evaluated urinary beta-core human chorionic gonadotropin (beta-core hCG) in the detection of fetal Down's syndrome (DS) in the first trimester of pregnancy. Urine was collected prior to performing chorionic villous sampling (CVS) between 10 and 12 completed weeks from the last menstrual period. In the 9 months of the study, there were 15 chromosomal abnormalities detected by CVS: five trisomy 21, four monosomy X, two trisomy 18, and four cases of confined placental mosaicism (CPM). In these 15 aneuploid pregnancies, the levels of urinary beta-core hCG were expressed as multiples of the median (MOM) of the ratio of beta-core hCG/creatinine for gestational age. The MOMs of this ratio in each of the five DS pregnancies were 0.2, 0.5, 1.3, 1.4, and 1.7. No difference was found between fetuses with DS or any of the other chromosomal abnormalities tested and normal fetuses. Contrary to optimistic reports of urinary beta-core hCG in the second-trimester detection of fetal DS, our data suggest that this is not a useful screening test for DS in the first trimester of pregnancy.