Abdominal separation is common in women who have pregnancies over 35, have delivered a large baby, had multiple pregnancies or had large weight changes during the pregnancy.  It can be seen in up to two-thirds of pregnant women in the third trimester. It is most apparent right after delivery of the baby and often gets better for the first several months after delivery.  You can also develop diastasis recti with abdominal obesity, this is more common in adult men.
Diastasis recti presents as a protruding bulge anywhere from the center of the upper abdomen between the belly button and the breast bone to a bulge below the belly button.  It might be noticeable only when the abdominal muscles are tense, such as during coughing or sit-ups.  Sometimes diastasis recti is misdiagnosed as a hernia.  It is not uncommon for a patient to initially be referred to a general surgeon for a hernia repair.  A good physical exam and imaging with a CT scan and occasionally an MRI will yield the correct diagnosis of diastasis recti.