Human chorionic gonadotropin exhibits normal biological activity in patients with recurrent pregnancy loss

To test the hypothesis that the structural abnormality of human chorionic gonadotropin (hCG) may induce recurrent pregnancy loss, we examined the biological activity of hCG in pregnant women with a history of repeated miscarriages (n = 44). Pregnant women without a history of miscarriage (n = 85) were included as controls. Serum hCG, estradiol (E2) and progesterone levels were found to be significantly lower in the pregnancy loss group. There was no difference in serum thyroid hormone levels. Sera from both groups of women were then incubated with Chinese hamster ovary (CHO) cells transfected with hCG/luteinizing hormone receptor (CHO-hCG/LHr) or human thyroid stimulating hormone receptor (CHO-hTSHr). Biological response to hCG in women with recurrent pregnancy loss was identical to that of women in the control group in both CHO-hCG/LHr and CHO-hTSHr cells. When sera were subjected to high performance liquid chromatography, no difference in hydrophobicity was observed between control and patients groups. The structure of the hCG molecule and its biological activity in women with a history of recurrent pregnancy loss are apparently not different from those in women with normal pregnancy. Lower serum progesterone and E2 levels in the patient group can be explained by lower serum hCG levels in these women. Intrinsic gonadotropic and thyrotropic activities of the hCG molecule appear to play no major role in recurrent pregnancy loss.