hCG is the pregnancy hormone made by the placenta that stimulates the ovaries to make estrogen and progesterone which thicken your uterine lining and tell your body to stop menstruating (or releasing eggs). hCG increases until about 10 weeks of pregnancy. hCG is the hormone that is used to detect early pregnancy. hCG can also be injected at mid-cycle in ovarian stimulation cycles and IVF cycles to stimulate ovulation.
