During pregnancy the majority of a woman’s abdominal muscles separate to make room for baby. This is normal and in the early postnatal period the muscles begin to repair and go back together.
Doing the correct exercises to aid recovery is important. While there is a gap there is a weakness and certain exercises, such as crunches or strong oblique work, can make this worse or cause the muscles to pull apart. Some exercises put too much pressure on the core and make the problem worse, press ups for example, or working on your hand and knees. If there is a gap then doing an exercise on all fours whilst working against gravity can be very challenging to keep the right muscles activated and literally to stop everything hanging out.
The aim with postnatal exercise is to bring the abdominals together and ensure that they are doing their job. Sometimes a gap remains but what is important is function that they are not doming when you are lying on your back or hanging out when on a fours.
Relaxin is an important hormone during pregnancy as it causes the joints to soften and loosen in the pelvis in preparation for delivery. Sadly relaxin doesn't just effect the pelvis, it effects all the joints in the body and it hangs around after delivery for 5 months oe 3 months after you stop breast feeding.
Avoiding high impact exercise is important as you are more prone to injury as the joints are less stable. Relaxin effects different people in different ways and tend to effect mums more the more children they have had.
When participating in exercise technique is key and it is important that you watch this or have an instructor that can keep an eye on you.