The vague pain in the lower abdomen at the beginning of pregnancy may be due to foreign body rejection of the endometrium when the embryo is transferred into the uterine cavity at the beginning of pregnancy. If there is no vaginal bleeding, you can observe and rest for the time being, and refrain from sexual intercourse and avoid stimulation by cold and spicy foods. After pregnancy, the progesterone level increases and the uterus becomes bigger and softer, which may cause soreness and vague pain in the lower abdomen. If the vague pain is obvious and there is vaginal bleeding, it is better to go to the hospital for gynecological ultrasound and blood test of HCG and progesterone to see if the embryo development is in accordance with the pregnancy week. In case of preterm miscarriage, early treatment with birth control medication should be given.