A great number of pregnant women wonder if their navel will pop out or go flat. The truth is, this varies on a case-by-case basis. However, all pregnant women have something in common in this sense: once the baby is born, the navel comes back to its normal position.
The reason why your belly button pops out during pregnancy is because it has to make room for the baby. At this point (5th month of pregnancy), your womb is so big that it puts pressure on your belly button, thereby causing it to alter its form to make room for it to continue getting bigger.
Typically, it recovers its normal shape and position once your abdominal muscles recover elasticity.