Maternal age and serum concentration of human chorionic gonadotropin in early pregnancy

Objective: To study whether maternal age is associated with serum concentration of human chorionic gonadotropin in early pregnancy.

Design: Cross-sectional study.

Setting: Oslo University Hospital in Oslo, Norway.

Population: All vital pregnancies in gestational week 8 conceived by in vitro fertilization between February 1996 and February 2013 (n = 4472).

Methods: Serum concentrations of human chorionic gonadotropin were measured on day 12 after embryo transfer/day 16 following ovulation induction. Trends in geometric means of human chorionic gonadotropin concentrations by maternal age group were tested by linear regression analysis. We also studied the association of maternal age (years) with log-transformed human chorionic gonadotropin concentrations, and adjustments were made for number of embryos transferred, method of in vitro fertilization and year (period) of embryo transfer.

Main outcome measure: Serum concentration of human chorionic gonadotropin.

Results: Geometric mean concentrations of human chorionic gonadotropin decreased with increasing maternal age (p = 0.024, test for trend by weighted linear regression). Also, we estimated a significant negative association of maternal age with log-transformed human chorionic gonadotropin concentrations (adjusted regression coefficient -0.011, standard error 0.003, p < 0.001).

Conclusions: Serum concentrations of human chorionic gonadotropin in very early pregnancy decreased with maternal age. Since human chorionic gonadotropin is synthesized in trophoblast cells only, the lower human chorionic gonadotropin concentrations in women of advanced age may reflect functional impairment or delayed proliferation of trophoblast cells in early pregnancy in these women.