High maternal serum free beta-hCG levels in Down syndrome pregnancies: a preliminary report.

To investigate the serum free beta-human chorionic gonadotropin (beta-hCG) value in women carrying Down syndrome fetus, we have retrospectively studied 11 Down syndrome pregnancies and 200 singleton unaffected pregnancies between 15 and 22 weeks' gestation. Each affected pregnancy was assigned at least 15 control cases matched with maternal age and gestational age. The median value of free beta-hCG in Down syndrome pregnancies and unaffected pregnancies was 2.56 multiples of the median (MoM) and 1.06 MoM, respectively. The mean free beta-hCG value after log transformation in Down syndrome pregnancies was 2.01 MoM that was significantly different from that of unaffected pregnancies (1.05 MoM, P = 0.024). There were 54.6% (6/11) of Down syndrome pregnancies and 5% (10/200) of unaffected pregnancies with free beta-hCG levels greater than 2.5 MoM. It is suggested that free beta-hCG may be a potentially useful and superior marker in the detection of Down syndrome pregnancies in our population.