So how does your belly expand during pregnancy. The truth is every woman's body is different on average a women will gain between 25 and 35 pounds per pregnancy. Because every woman's body is different your belly may start to show at 2 months or not until 6 months. If this is your first baby sometimes it takes a little bit longer for your belly start to begin to show. You might feel like you are just beginning to gain a little weight and looking little chunky and soon enough you, your family and friends will all be able to tell that you are growing a beautiful baby inside. You may notice your body changes. You may develop what's called the linea nigra, which is a dark line from your belly button to your pubic bone. This is just a common skin change that happens during pregnancy and nothing to be concerned about. It usually goes away a few months after you give birth. You may develop some stretch marks; these are some loving imprints from your baby that are a gift to you. If you are concerned about stretch marks you can use coconut oil or other lotions to help diminish their disappearance.