Sudden backache and bleeding in the 7th month of pregnancy, this situation should be considered whether it is preterm labor, whether there is placenta praevia or placenta previa, and so on, and you need to go to the hospital for examination in time. 1. Preterm labor: If you are 7 months pregnant and have back pain and vaginal bleeding, you should first consider whether it is preterm labor. If it is preterm labor, when the uterus is contracting, the pregnant woman will feel soreness or pain in the abdomen, and the stomach will be tight or hard for a while. 2. Placenta praevia: If the pregnant woman only feels soreness in the lower back, no pain in the stomach, and the bleeding is bright red, it is necessary to consider whether the placenta praevia. If it is placenta previa, ultrasound examination will find that the placenta is lower than the fetal prenatal part, attached to the lower part of the uterus, the lower edge of the uterus reaches or covers the cervical opening. 3. Placental abruption: If the pregnant woman not only has back pain, but also abdominal pain, vaginal bleeding and other symptoms, and ultrasound examination reveals that there is a liquid hypoechoic area between the placenta and the wall of the uterus with unclear edges, then we should consider the possibility of placenta abruption.