Diastasis recti (also known as abdominal muscle separation) is the stretching/weakening of the linea alba and the entire abdominal wall that occurs during pregnancy. It usually happens during later stages of pregnancy and sometimes doesn’t go back together afterwards, which is why you still have that “mummy tummy.”
Gap of 2 fingers after childbirth is quite normal. But please note it’s not just about how wide the gap is but also how deep it is too.
Diastasis recti reduces the integrity and functional strength of the abdominal wall and can aggravate lower back pain and pelvic instability. You need to understand how to help your muscles to heal and how to decrease the intra-abdominal pressure pushing onto them. And you need to be aware of what NOT to do, as some very poplar exercises (e.g. sit-ups, planks, and push-ups) will make it worse. Your abdominal wall needs a degree of loading to heal, but it requires the right kind and amount at the right time.
I always recommend to see women’s health physio post birth and they can check for your abdominal separation. But if you would like to check it yourself below video shows you how to do it.