If the menstrual period did not come, the pain in the stomach after intercourse may be caused by the following reasons: First, whether it is pregnant, after intercourse, stimulation caused by uterine contraction, and the symptoms of a priori miscarriage, so there will be pain in the lower abdomen, it is recommended to do the blood HCG laboratory tests, clinically can be a clear diagnosis. Secondly, it may be caused by ectopic pregnancy, ectopic pregnancy is mostly localized pregnancy in the fallopian tube, after coitus will form a stimulus, which will also lead to local bleeding phenomenon, so it will cause pain in the lower abdomen, through the examination can be clearly diagnosed, and actively intervene in the treatment. Third, it may be due to endocrine disorders, menstruation has not come, the original and pelvic inflammatory disease, coitus will aggravate the pelvic congestion, so there will be stomach pain.