As progesterone softens ligaments and relaxes muscles in the body, it may cause the round ligaments, which suspend the enlarging uterus, to stretch and cause pain. These feel like pulling sensations in the right and left lower quadrants of the abdomen and are most annoying. They decrease in intensity in the second and third trimester. Progesterone also relaxes the bowel and slows it down, causing constipation and gas. Make sure you eat a diet high in fiber, at least 12 grams per day.
Most cereals have only one to five grams, but the less-processed cereals and breads have much more.
Bran is especially good. Though most anti-gas and antacid preparations are okay to use in pregnancy, check with your pharmacist and provider before using one. The absolutely best thing for gas in pregnancy is exercise. Even gentle stretching and yoga stimulate the bowel and get things moving. As the uterus grows and pushes up into the abdomen, it will move off the large intestine to some degree, which will also help.