That said, lower abdominal pain during the third trimester usually isn't anything to worry about. Here are some of the most common causes of lower abdominal pain in the third trimester.
Digestive Pain
Lower abdominal pain during the third trimester may or may not actually relate to pregnancy. Your digestive tract is very close to your uterus, so it's easy to mistake digestive upsets for pregnancy complications. Gas, anxiety, food intolerance, constipation and infection can call cause lower abdominal pain, both during pregnancy and at other stages in life. However, if the problem is severe or persistent, it's a good idea to talk to a professional.
Round Ligament Pain
Round ligament pain is extremely common during third trimester. As your uterus stretches to accommodate your unborn baby's growth, it strains the ligaments and muscles surrounding your womb. This can cause pain, especially in the round ligament, which is on the left side of your lower abdomen. Most women experience round ligament pain as a mild, dull ache on the left side of the lower abdomen. It may vary in its intensity, sometimes becoming a sharp but brief cramp.
Practice Contractions
Practice contractions, known clinically as Braxton-Hicks contractions, are usually painless. However, a few women will experience mild cramping during these exercises, which help to prepare the uterus for labor. If you do experience lower abdominal pain from practice contractions, it should be mild, brief and irregular. Regular or severe pains may signal the onset of labor.
Labor
Lower abdominal pain during the third trimester can be a sign of impending labor, especially if you are past 36 weeks. If your pains are regular, occurring for more than a few seconds and returning more than every 10 minutes, you may be in labor. Watch for other signs of labor, such as bloody show, mucus discharge and ruptured membranes. Call your health care provider promptly if you are before 36 weeks.