Around 16 to 18 weeks into a pregnancy, women start to feel the baby making movements. There is large variation between women and the feeling of a baby moving is not the same for every woman, which makes it hard for a woman to determine if the feeling is gas bubbles moving through the body or is the baby moving instead. It is easier to tell if it is the baby moving later during pregnancy, when the baby is kicking and punching, but the start of movement is easily confused with gas bubbles.
Pay attention to how often the feelings occur. If the feelings are few and far between, it is likely gas bubbles. If the feelings are almost constant, it is the baby moving. Gas bubbles are few and far between rather than constant or often, but an active baby might move and stretch almost constantly.
Look at the time of the pregnancy. Most women begin to feel the first movements around 18 to 22 weeks. The feelings can start as soon as 15 or 16 weeks, but this is less common for most women. If it is earlier than 15 weeks, the feeling is not likely the baby.
Look at your size. A smaller woman will feel the baby moving sooner than a larger woman. Women that feel the baby around 16 weeks are usually small while women that feel the baby later are usually larger.
Consider the feeling. The first movements a woman can feel and gas bubbles often feel similar. If it seems like the feelings are similar to a butterfly in the tummy feeling, it is likely the baby rather than gas.
Look at where the feeling comes from. If the feeling is always in the same area, such as by the left rib, it is the baby. Gas bubbles will always move while going through the system, but a baby's movement will remain in the same place.
Pay attention to whether gas is passed shortly afterward or not. If gas is not passed after a short time, it is the baby moving. Gas bubbles will eventually pass out of the system, but a baby's movements will not.