Diastasis recti is a separation of the abdominal muscles that's very common during pregnancy (occurring at rates of 66% to 100% of women in their third trimester) and shortly after. During pregnancy, the growth of the uterus stretches the muscles in the abdomen. The separation often resolves naturally within 8 weeks after delivery, but when it doesn't it may cause lower back pain and instability.
If you think you have diastasis recti, talk to your health care provider. While pregnant, there is no treatment, but there are certain exercises that can help prevent or reduce the size of the separation after delivery.
After childbirth, exercises are often prescribed to strengthen the abdominal muscles. A physical therapist can help develop a specialized exercise plan for treating diastasis recti.