When women experience menstrual pain in the abdomen in the second trimester, two possibilities are considered: first, the pain is caused by the stimulation of the uterus after the fetus has descended into the pelvis, mainly due to vague pain in the abdomen, and the vague pain will persist. Secondly, it is considered that the fetus has matured at full term and the hormonal stimulation in the body has caused contractions in the uterus, resulting in pain in the small abdomen. Many pregnant women may experience a formal onset of labor soon after the onset of menstrual pain. For women who are not more than 37 weeks pregnant, it is best to rest in bed and avoid too much activity to avoid preterm labor, and for women who are already full term, they can just let nature take its course and wait for the onset of labor.