The main reason for back pain after having a baby is infected gynecological inflammation, pelvic floor muscle relaxation, lumbar muscle strain and other reasons. 1. Infection of gynecological inflammation, such as postpartum pelvic inflammatory disease or endometritis, then the pelvis or the uterus will form fluid, so that after coitus stimulation will be easy to appear the symptoms of lumbago, to use medication, such as amoxicillin and so on. 2. Pelvic floor muscle relaxation, in the process of pregnancy and birth, the pelvic floor muscle is constantly subjected to heavy pressure it will lead to the stability of the lumbar spine decreased, which may cause low back pain. Pelvic floor muscle relaxation caused by low back pain, then you need to repair the pelvic floor muscle instrument. 3. Lumbar muscle strain is mainly due to improper or excessive force during labor, resulting in lumbar muscle injury is also prone to postpartum coital pain. It can be treated by physical therapy, such as microwave with massage therapy. In this case, don’t have intercourse first, we should consult the doctor in time to find the reason for treatment, to avoid delaying the condition.