When it comes to pregnancy, the female body is pretty amazing—it grows, changes and stretches to accommodate a 7- to 9-pound baby (give or take), and then (not immediately, but with time), reverses the process and returns to "normal"...mostly.
As the belly grows through the third trimester, all women experience a separation down the center of the abdomen as the rectus abdominis muscles (commonly referred to as the "six-pack muscles") stretch apart to accommodate the growing baby. This separation is called diastasis recti, and it's a completely normal and expected part of pregnancy.
Even though diastasis recti is normal during pregnancy, there are circumstances postpartum where you may determine you need additional help with "closing the gap," so to speak, down the center of your abdominals.
"During pregnancy, the strong connective tissue connecting the two sides of our rectus abdominis muscles stretches to accommodate our burgeoning belly," explained Angela Fishman, a licensed physical therapist specializing in pelvic floor physical therapy.