Maternal body mass index and serum concentrations of human chorionic gonadotropin in very early pregnancy

Objective: To study the association of maternal prepregnancy body mass index (BMI) with serum concentrations of hCG in early pregnancy.

Design: Cross-sectional study.

Setting: Oslo University Hospital, Norway, 1996-2010.

Patient(s): Among 3,301 pregnancies with live-born offspring conceived after assisted reproductive techniques, 2,611 women had information on serum hCG concentrations on day 16 after ovulation induction and prepregnancy BMI: 2,110 mothers with singleton and 501 mothers with multiple pregnancy.

Intervention(s): None.

Main outcome measure(s): Human chorionic gonadotropin concentration.

Result(s): Geometric mean hCG concentration was higher in multiple pregnancies (190 IU/L) than in singleton pregnancies (106 IU/L). In singleton pregnancies geometric mean serum concentration decreased from 117 IU/L in women with BMI <20 kg/m(2) to 86 IU/L in women with BMI ≥ 35 kg/m(2). In multiple pregnancies, the corresponding decrease was from 226 IU/L to 130 IU/L. There was a significant negative association of BMI with hCG concentrations log transformed in the study sample as a whole (regression coefficient -0.013), in singleton pregnancies (regression coefficient -0.012), and in multiple pregnancies (regression coefficient -0.03).

Conclusion(s): Serum hCG concentrations were negatively associated with maternal prepregnancy BMI. One possible explanation may be an effect of adipose tissue-derived signaling molecules on hCG secretion by the implanting embryo.