Maternal urinary beta-core fragment of hCG/creatinine ratios and fetal chromosomal abnormalities in the second trimester of pregnancy.

Our aim was to evaluate the potential value of the ratio of the maternal urinary beta-core fragment of human chorionic gonadotropin (beta C-hCG) to creatinine (Cr) in discriminating between normal pregnancies and pregnancies associated with fetal chromosomal abnormalities. We hypothesized that pregnancies with fetal chromosomal abnormalities had abnormal quantities of beta C-hCG in the urine. The aims of the present study were to investigate retrospectively whether maternal urinary ratios of beta C-hCG/Cr are abnormal in women carrying fetuses with chromosome aberrations and to determine normative median values and a reference range for beta C-hCG/Cr between 14 and 19 weeks' gestation. Maternal urinary beta C-hCG and Cr concentrations were measured in 150 healthy women from 14 to 19 weeks and compared with ten cases of fetal chromosomal abnormalities matched for gestational age. The preliminary cut-off points corresponded to 0.29 multiple of the normal median (MOM) and 2.83 MOM, which were equivalent to the tenth and 90th centiles of the normal range. Of ten cases of fetal chromosomal abnormalities, one out of one (100 per cent) case with trisomy 18 and three of four (75 per cent) cases of variant 9 chromosomes had low beta C-hCG/Cr (< or = 0.29 MOM). One of five (20 per cent) cases with Down syndrome had elevated beta C-hCG/Cr (> or = 2.83 MOM). Urinary beta C-hCG/Cr ratios obtained in the second trimester may be useful for improved detection efficiency of Down syndrome, trisomy 18, and inversion of chromosome 9. Second-trimester maternal urinary beta C-hCG/Cr should be investigated further as a potential marker for fetal chromosome anomalies.