Maternal Serum Free Beta-Human Chorionic Gonadotropin Levels between 14 and 21 Weeks of Gestation in Thai Pregnant Women

Abstract

Objective to determine normative median values for maternal serum free beta-human chorionic gonadotropin (ß-hCG) between 14 and 21 weeks of gestation in Thai pregnant women.

Methods We measured the concentrations of maternal serum free B-hCG from 836 healthy singleton Thai pregnant women between 14 and 21 weeks of gestation. The maternal age on the day of delivery and maternal weight at the time of sampling were recorded in all cases. Gestational-specific medians for maternal serum free B-hCG were calculated by weighted non-linear regression from the observed medians of each gestational week.

Results The median levels of maternal serum free B-hCG had a downward trend in association with the increase gestational age and these were higher than those of white pregnant women. Of pregnancies with free beta-hCG levels, there were 2.75% and 14.11% less than 0.3 and 0.5 MOM, respectively; 13.40%, 6.34% and 4.90% had serum levels greater than 2.0, 2.5 and 3.0 MOM, respectively.

Conclusion to allow for differences in maternal serum free B-hCG median values at various ages of gestation, establishment of the reference range is essential for further development of maternal serum screening for Down syndrome.