Abdominal bloating is a condition in which the abdomen (belly) feels full and tight, usually due to gas. This uncomfortable feeling, unfortunately, is very common in pregnancy and tends to get worse in the later stages of pregnancy.
Progesterone, a pregnancy hormone, causes the gastrointestinal tract to relax and slow down digestion. This is the same reason that constipation occurs during pregnancy. This allows the nutrients from your food to enter your bloodstream and reach your baby, but the slower metabolism also leads to bloating.
As your baby grows and your uterus expands, they'll press more on your stomach and intestines. This is why you'll feel more bloating during the later stages of your pregnancy.