Once you've delivered your baby, hormone levels return to their pre-pregnancy levels, and that thinning generally improves. But in many cases, the tissues get so stretched out during pregnancy that they lose their elasticity and, therefore, the ability to retract back into position -- kind of like an overstretched rubber band.

It's very common among pregnant women. About two-thirds of pregnant women have it.

Having more than one child makes this condition more common, especially if they’re close in age. Chances are higher when you are over 35 when pregnant, or if you’re having a heavy baby, twins, triplets, or more.
Pregnancy puts so much pressure on the belly that sometimes the muscles in front can’t keep their shape. "Diastasis" means separation. "Recti" refers to your ab muscles called the "rectus abdominis."

When the ab muscles move aside like this, the uterus, bowels, and other organs have only a thin band of connective tissue in front to hold them in place. Without the needed muscle support, a vaginal delivery could be more difficult.

The condition also can cause lower back pain, constipation, and bladder leakage. It can even make it hard to breathe and move normally. It's rare, but in extreme cases, the tissue may tear, and organs may poke out of the opening -- that’s called a hernia.

The muscle opening often shrinks after giving birth, but in some studies of women with diastasis recti, the muscle never returned to pre-pregnancy.