HCG, also known as human chorionic gonadotropin, is a hormone secreted by the trophoblast cells of the embryo in the early stages of pregnancy. As the fetus grows, the hormone gradually rises in the woman’s body, and the number generally increases exponentially after 48 hours in the early stages of pregnancy. If a sudden drop is noticed when it is rising, it usually does not rise again. The first thing to consider when this happens is that the embryo is not developing well, because the hormone is secreted by the embryo, and if it drops, it is possible that the embryo is not developing well. Clinically it is more common for the embryo to stop developing before the possibility of HCG drop occurs. If this happens, you need to go to the hospital as soon as possible to do an ultrasound to confirm whether the embryo development is normal or not.