WebMD reports that excessive gas is an extremely common symptom of pregnant women and may start early in the pregnancy. Hormone changes can slow down gastrointestinal functions, causing bloating, while decreased muscle control during pregnancy can make it harder to withhold flatulence.
What to Expect explains that progesterone, an essential hormone for pregnancy, causes soft muscle tissue to relax, including the gastrointestinal tract. This relaxation is intended to slow down the passing of nutrients through the body so that the fetus can receive nourishment from foods. This can cause bloating, which exacerbates the effect of the expanding uterus pushing against the rectum. Healthy doses of water and moderate amounts of fiber-rich foods can speed the digestive system up, and smaller meals can also decrease gas pressure.