The hidden pain in the abdomen on the 35th day of pregnancy may be caused by physiological reasons, pre-miscarriage, ectopic pregnancy and other reasons. 1. Physiological reasons: at the beginning of pregnancy, some pregnant women may experience a small amount of vaginal bleeding during the fertilization of the egg, accompanied by a slight pain in the abdomen, usually lasts for 3-4 days and will gradually return to normal, is a physiological phenomenon that does not require special treatment. 2. Pre-eclampsia: It can also cause vague pain in the lower abdomen, accompanied by a small amount of vaginal bleeding, part of the pregnant women ultrasound can be clear intrauterine pregnancy, progesterone and blood HCG (human chorionic gonadotropin) levels may be low or doubled unsatisfactory, need to follow the doctor’s instructions to preserve the fetus treatment. 3. Ectopic pregnancy: there will also be vague pain in one side of the lower abdomen, accompanied by irregular vaginal bleeding, need to be combined with ultrasonography, blood HCG test to assist in the diagnosis. When you are pregnant for 35 days, you need to go to the hospital to find out the cause of the pain and actively deal with it.