The following are possible reasons for the pain in the stomach when pregnant: 1. Pre-eclampsia, which is usually accompanied by redness in addition to pain in the stomach, which is a sign of vaginal bleeding. 2. Ectopic pregnancy, which causes pain in the stomach, is an emergency and serious condition that requires timely treatment, otherwise it may easily cause hemorrhagic shock or endanger life. 3. For example, acute gastroenteritis leads to intestinal cramping pain, which is usually accompanied by nausea, vomiting and diarrhea. So if you are pregnant and have a pain in your stomach, it is recommended to go to a regular specialist hospital to improve the relevant examination and give timely and effective symptomatic treatment after a clear diagnosis.