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

ObjectiveTo study the association of maternal prepregnancy body mass index (BMI) with serum concentrations of hCG in early pregnancy.DesignCross-sectional study.SettingOslo 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/m2 to 86 IU/L in women with BMI ≥35 kg/m2. 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.