Human Chorionic Gonadotropin (hCG)

Human Chorionic Gonadotropin (hCG) is a hormone the early placenta produces soon after an embryo implants. The cells that produce it form the outer layer of the early placenta (the syncytiotrophoblast). Pregnancy tests detect one part of the hormone, the beta subunit (beta-hCG). Its first role is to sustain the corpus luteum. This small gland forms in the ovary after ovulation. It produces progesterone, which an early pregnancy requires. Without hCG, the gland shrinks and progesterone falls. The pregnancy can then end before the placenta is ready to produce its own progesterone. The placenta takes over at about 7 to 9 weeks. hCG also helps the mother's immune system accept the baby. In a male baby, it helps the early testes produce testosterone.

The structure of hCG closely resembles that of LH, the hormone that triggers ovulation. Both bind the same receptor. This resemblance gives hCG two clinical uses. An injection of hCG can substitute for the body's own LH surge and trigger ovulation. Repeated injections after ovulation can also support a weak corpus luteum through the luteal phase. RRM clinicians may time this support to the woman's charted cycle. The goal is to support what her body is already working to do.

Researchers have also tested hCG in recurrent pregnancy loss. Quenby and Farquharson conducted a randomized, placebo-controlled trial in 81 women whose repeated losses had no identified cause. Some of these women had long, irregular cycles (oligomenorrhea). In that group, the pregnancy success rate was 40% on placebo. With hCG, it rose to 86%, a statistically significant gain. Women with regular cycles did equally well with or without hCG.¹ Cycle pattern shaped which women benefited.

Serial measurement of hCG levels is a key tool in early pregnancy. In a healthy early pregnancy, levels climb quickly. A slow rise or a plateau calls for a prompt search for the cause.