Bleeding in 3-4 months of pregnancy can be caused by pre-eclampsia, ectopic pregnancy, gravida, pregnancy combined with cervical erosion and external stimulation. 1, aura miscarriage: if the pregnant woman in the hospital examination is clearly for intrauterine pregnancy, 3-4 months of pregnancy vaginal bleeding, no abdominal pain or abdominal pain, there is the possibility of aura miscarriage. Need to go to the hospital as soon as possible, should carry out gynecological examination, to exclude cervical and vaginal pathology caused by bleeding, consider the preeclampsia, carry out ultrasound examination, the fetus survives well, give birth control treatment. If the fetus stops developing, abortion and induction of labor will be given. 2, ectopic pregnancy: if the pregnant woman has not been clear intrauterine pregnancy, only at home urine test paper positive, 3-4 months pregnant bleeding does not exclude the possibility of ectopic pregnancy, such as accompanied by abdominal pain, abdominal mass, or even fainting, shock and other life-threatening, need to seek medical attention as soon as possible. 3.Grape fetus: positive urine pregnancy test, should go to the hospital for blood HCG test and ultrasound as soon as possible for a clear diagnosis, diagnosed as a grape fetus need to be hospitalized as soon as possible to carry out the purging operation. 4, vaginal and cervical lesions: 3-4 months after menopause, vaginal bleeding may also be caused by vaginal and cervical lesions, any situation of vaginal bleeding should be gynecological examination, to understand the location of the bleeding, the cause of the bleeding is clear, only for the cervical erosion of the bleeding is not treated during pregnancy; such as vaginal and cervical masses need to be clear about the benignity or malignancy of the masses, and then choose the treatment plan. In short, if you are 3-4 months pregnant and find vaginal bleeding, no matter what the cause is, you need to consult a doctor in time.