Pre-pregnancy stomach pain like menstruation may be caused by early pregnancy symptoms, miscarriage with precursor, ectopic pregnancy and other reasons. 1. Early pregnancy symptoms: some women will experience physiological signs and symptoms during early pregnancy, which may include painful uterine contractions not accompanied by vaginal bleeding, lower abdominal discomfort, bloating, constipation and other symptoms similar to lower abdominal pain during menstruation. 2. Pre-eclampsia: Miscarriage can occur due to environmental factors such as poor sperm quality of the father, maternal infection, anemia, endocrine diseases, chromosomal abnormalities of the embryo. Early miscarriage embryo stripping or bleeding stimulate uterine contraction, causing paroxysmal lower abdominal pain, similar to menstrual lower abdominal pain. 3. Ectopic pregnancy: the fertilized egg in the fallopian tube in the bed, when the embryo in the fallopian tube gradually grows, ectopic pregnancy rupture or miscarriage before, often manifested in the lower abdomen or one side of the lower abdominal pain. In the early stage of miscarriage of ectopic pregnancy, a small amount of blood stimulates the peritoneum, which can cause hidden pain in the lower abdomen, similar to the lower abdominal pain during menstruation. Therefore, patients with lower abdominal pain during early pregnancy need to consult a doctor to determine the cause of the problem and give appropriate treatment.