Urine free beta-human chorionic gonadotropin levels between 14 and 21 weeks of gestation in Taiwanese pregnancies.

BACKGROUND: The purpose of this study was to determine the reference range of maternal urine free beta-human chorionic gonadotropin (beta -hCG) concentrations between 14 and 21 weeks of gestation. METHODS: We measured the concentrations of urine free beta -hCG from 268 healthy singleton Taiwanese pregnancies between 14 and 21 weeks of gestation. Results were corrected for creatinine (Cr) concentration and converted to the multiple of the median (MOM) level for the appropriate gestation. Gestational ages of all cases were determined using ultrasound dating. RESULTS: The median levels of urine free beta -hCG and free beta-hCG/Cr had a downward trend in association with the increasing gestation age. The median, 5th, 10th, 90th and 95th centiles of free beta- hCG/Cr MOM values were 1.02, 0.20, 0.25, 2.32 and 3.38 MOM, respectively. Urine free beta- hCG/Cr MOM values showed a log Gaussian distribution with the mean and standard deviation (SD) distribution of -0.0657 and 0.3792, respectively. CONCLUSION: To allow for differences in free beta -hCG/Cr median values at various ages of gestation, establishment of the reference range is essential for further development of maternal urine screening for Down syndrome.