During embryonic development, the testes originate in the abdomen near the kidneys. Late in the developmental process, around the seventh or eight month of pregnancy, the glands move into their lower position within the scrotal sac. This change of position is regulated by the male sex hormone testosterone, the secretion of which is stimulated by the hormone called chorionic gonadotropin exuded by the placenta. Occasionally, the testes do not descend properly, remaining within the abdomen even after birth. In such cases, medical treatment is usually necessary in order to avoid sterility.