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Some belly discomfort is expected during pregnancy; after all, there are a lot of changes going on as baby grows. But what’s normal and what’s not? “With any unfamiliar pain, check in with your doctor,” says Lisa Gittens-Williams, MD, associate professor and director of obstetrical services at Rutgers New Jersey Medical School. “Signs that you should be seen immediately include abdominal pain accompanied by bleeding or a change in vaginal discharge, which could indicate preterm labor.”

Here are the most common causes of belly discomfort during pregnancy:

ROUND LIGAMENT PAIN

“This type of pain is a stretching or pulling sensation as the body accommodates the growing baby,” says Damali Campbell, MD, an assistant professor at the department of OB-GYN and women’s health at Rutgers New Jersey Medical School. “These ligaments are on the sides of the abdomen, so you may feel pain on both sides of the belly radiating toward the vaginal area.” It typically occurs in the second trimester. The discomfort usually subsides on its own, but wearing a pregnancy belly band can help support your growing waistline.

INDIGESTION AND GAS

“Progesterone, which increases during pregnancy, slows down digestion,” says Campbell. “Even when you eat foods that never bothered you before, you may experience a feeling of gassiness, over-fullness, nausea or pain in your upper abdomen.” It’s fine to pop a TUMS. To prevent future episodes, eat five or six smaller meals throughout the day instead of three big ones.

CONSTIPATION

Prenatal vitamins, especially iron, may cause you to skip the bathroom for days, causing belly pain, says Campbell. Increase your water intake (you should be downing eight or more glasses a day), eat a high fiber diet and ask your doc about taking a stool softener.

ECTOPIC PREGNANCY

This is a serious condition in which a fertilized egg grows outside the uterus, usually in a fallopian tube. Symptoms include sudden severe pain in the abdomen or pelvis, weakness, dizziness or fainting. If you have belly pain and a positive pregnancy test but haven’t had it confirmed by an actual exam, get evaluated immediately by your OB-GYN, says Gittens-Williams.

BRAXTON-HICKS CONTRACTIONS

Also known as “false labor,” these contractions are irregular and typically occur during the third trimester. “It feels like a squeezing sensation or a band tightened across the whole abdomen,” says Gittens-Williams. Time the contractions: If they occur once or twice and then stop, no worries. If you have four in 30 minutes or eight in an hour, it may represent preterm labor and you must be seen by a doctor immediately.

PRETERM LABOR

If you’re having regular contractions before your 37th week, you may be in preterm labor. Other symptoms may include bleeding, a change in the type or amount of vaginal discharge, pelvic or lower abdominal pressure, cramps or backaches. Call your doctor ASAP: “If you don’t get a call back within 15 minutes, head to the ER,” says Campbell.

PREECLAMPSIA

This pregnancy complication characterized by organ damage and high blood pressure usually occurs after the 20th week of pregnancy, typically in the third trimester. It’s not clear why some women develop preeclampsia, but risk increases in women who are pregnant for the first time, have a history of high blood pressure, are older than 40 or are carrying multiples. Although belly pain isn’t usually the only symptom (other signs include severe headache, facial swelling and vision changes), if you’re experiencing this in addition to pain in the upper abdomen or shoulder, call your doc for an evaluation ASAP.