Hardening of nipples in early pregnancy is a normal physiological phenomenon. At the beginning of pregnancy, the secretion of estrogen and progesterone increases, especially progesterone, which promotes the growth of breast follicles, while estrogen promotes the growth and development of breast ducts. The enlarged and developed mammary glands will be more sensitive, which will make the nipple hard. In this case, women should wear loose underwear to avoid irritation of the nipple. If the nipple often becomes hard, it will also irritate the uterus, causing it to contract, and preeclampsia will occur. In the early stage of pregnancy, a woman must keep her mood stable, have regular obstetric checkups, and do ultrasound to observe the growth and development of the embryo. If the embryo develops well, the fetal heartbeat is within the normal range, and there is no lower abdominal pain or vaginal bleeding, regular checkups in the future will be sufficient.