There are many reasons for stomach pain during pregnancy, for example, when progesterone or human chorionic gonadotropin tends to decrease, stomach pain may also occur, which may indicate the possibility of pre-eclampsia. Tummy pain can also occur when constipation is caused by bowel disorders. Having intercourse on the 20th day of pregnancy can also cause stomach pain if it irritates the uterus and vaginal walls. In this case, first of all, go to the hospital for a blood test of progesterone and blood HCG, to rule out any abnormality, according to the situation can be prescribed to keep the fetus medication, such as progesterone to keep the fetus for 7-10 days, and then review, to avoid the occurrence of miscarriage.