What causes cramping in early pregnancy

Cramping during pregnancy can feel scary, but it's a common symptom throughout all trimesters. Most mild abdominal cramps aren't dangerous; in fact, they're simply the uterus's response to anything that's happening to it. "The uterus is a muscle, and the only thing a muscle knows how to do is contract, and a contraction feels like a cramp," explains Holly Puritz, M.D., medical director for Sentara Leigh Hospital Group for Women in Norfolk, Virginia.

That means whenever your uterus is stimulated—by a full bladder, vigorous exercise, or something more—its natural response is to contract. The important thing, says Dr. Puritz, is to figure out when cramps during pregnancy are normal and when they are cause for concern. Keep reading for our trimester-by-trimester guide to cramping during pregnancy.

"The majority of pregnancies will have some mild (light) cramping intermittently during the first 16 weeks," says Chad Klauser, M.D., Clinical Assistant Professor of Obstetrics and Gynecology at the Mount Sinai School of Medicine in New York City. Here are some common causes of first-trimester cramping.

For some people, cramping is one of the first signs of pregnancy, as it sometimes happens when a fertilized egg burrows in the uterine wall. This is called implantation cramping, and it can feel like your period is about to start, says Dr. Puritz.

Rapid uterine growth in the first two trimesters of pregnancy can also lead to a pulling sensation within the abdomen, says Dr. Klauser. Your uterus must stretch and expand to accommodate your growing baby.

Changing hormone levels might cause increased gas, bloating, and constipation during the first trimester. All of these gastrointestinal issues can cause cramping sensations.

In rare cases, first-trimester cramping could be caused by ectopic pregnancy (when the embryo implants outside of the uterus, usually in the fallopian tube). Ectopic pregnancy often involves one-sided cramping, bleeding, lightheadedness, or shoulder pain. Contact your doctor immediately if you have symptoms of ectopic pregnancy.

Miscarriages most commonly happen because of abnormal development in an egg or embryo (usually caused by chromosomal abnormalities). The cramping associated with miscarriage happens when blood and tissue leave the uterus, causing it to contract. Aside from cramping, the most telltale sign of miscarriage is heavy bleeding that doesn't let up. Contact your doctor right away if you suspect miscarriage.

Pregnant people are less likely to experience cramping or other uncomfortable pregnancy symptoms during the second trimester. One exception is anyone pregnant with multiples since the uterus grows more rapidly and will reach third-trimester proportions in the second trimester. Here are some other causes of second-trimester pregnancy cramping.

This benign pain can begin around week 13 when the ligaments that support the uterus stretch as the uterus grows upward. Round ligament pain is usually quick, sharp, and can feel like a pulling/tugging sensation. It can be one-sided or appear on both sides.

Mild urinary tract infections (UTIs) can also cause cramps during pregnancy in the second trimester. Other symptoms includepainful urination, the frequent need to pee, and lower abdominal discomfort. Contact your doctor if you think you have a UTI.

A more serious but rare cause of cramping is uterine fibroids. These harmless overgrowths of tissue can start breaking down in the second trimester (usually between 15 and 18 weeks of pregnancy) because there's not enough blood to sustain their growth. The pain is severe. Any person with a history of uterine fibroids should watch for pregnancy cramps at this point because they may need hospitalization to manage the pain effectively until it passes.

By the time you get to your third trimester, your body will be so busy doing so many things that cramping may begin to feel like just a part of your routine. From baby kicks and indigestion to "practice" contractions and even pre-term labor, there are many reasons for cramping this late in the game. Here are three common reasons.

It's very common for pregnant people to experience cramping in the third trimester—often in the form of Braxton Hicks contractions. These "false" or practice contractions don't actually progress into labor, but they can help prepare your body for delivery. While Braxton Hicks contractions only last between 30 seconds and two minutes, you can often relieve symptoms by drinking some water, changing positions, and resting.

Of course, if third-trimester cramping doesn't quickly subside and continues to progress, you could be experiencing preterm labor, which is labor that begins before 37 weeks of pregnancy. Call your doctor right away and express your concerns; they might want to evaluate you right away. Some signs of pre-term labor include can change in vaginal discharge, water breaking, and regular contractions.

Other serious causes of cramps during the third trimester include placental abruption (when the placenta separates from the uterine wall) and preeclampsia (a condition characterized by sudden high blood pressure). Call your doctor for cramping accompanied by bleeding, severe headaches, shortness of breath, swelling, or vision changes.

• RELATED: Signs of Preterm Labor and What Your Doctor Will Do

Sometimes cramping is normal during pregnancy. According to experts, you shouldn't worry about cramping after sex, whether partnered or solo. "Intercourse is one of the most common causes of cramping," says Dr. Puritz.

With vaginal penetration—whether with a penis, fingers, or toy—you can come into contact with the cervix, which can cause some mild cramping if bumped or stimulated. Additionally, semen contains prostaglandins that can stimulate the uterus, so if you have penis-in-vagina sex and your partner ejaculates near your cervix, you may experience some cramping after. Last but certainly not least, orgasm can lead to temporary uterine cramping.

Dr. Puritz adds that for most pregnant people, it's completely fine to have sex, and if you have cramps afterward, try getting off your feet and hydrating.

It's also a good sign if changing position makes cramps better or worse.This generally means you're experiencing cramps related to stretching of the uterus or its supporting ligaments, which is completely normal during pregnancy. Finally, if you feel better after passing gas, the pain is likely related to a gastrointestinal problem instead of the uterus, says Dr. Klauser.

On the other hand, certain scenarios indicate that something more serious could be happening. Watch out for the following red flags and inform your doctor ASAP if you notice them.

Having six or more contractions in an hour could be a sign of preterm labor. Also, watch for other symptoms of preterm labor, including changes in vaginal discharge, pelvic pressure, and dull backaches.

It's especially important to call your doctor or midwife if you experience cramping and other symptoms like dizziness, lightheadedness, or vaginal bleeding if you haven't yet confirmed your pregnancy with an ultrasound as it could be a sign of an ectopic pregnancy. Bleeding can also be a symptom of miscarriage or placenta previa, a condition in which the placenta covers the cervix.

If you have persistent cramping and you are pregnant with multiples (which increases your risk of preterm labor), have a history of preterm labor or ectopic pregnancy, or have been diagnosed with a shortened cervix, call your doctor.

Back cramping and/or pain in your abdomen area could be symptoms of appendicitis, kidney stones, or gallbladder disease.

It's also important to get checked out if changes in physical position and time don't alleviate the cramping sensation.

Symptoms of preeclampsia include pain in the upper-right side of the abdomen, headaches, swelling, vision changes, and sudden weight gain. These usually show up in the third trimester.

If you have pregnancy cramps that don't seem worrisome, Dr. Puritz advises getting off your feet, resting, drinking fluids, and taking acetaminophen (such as Tylenol) if needed for pain relief. Don't use a heating pad on your abdomen because raising your core temperature is dangerous during pregnancy, especially in the first trimester. (Using one on your extremities, however, is fine, Dr. Puritz says.)

Dr. Klauser also recommends trying a warm shower. Stretching and sitting breaks throughout the day can also be helpful, particularly if you find that your cramping is worse after long periods of being in one position.

Most importantly, always contact your prenatal care provider for unusual cramps or ones that don't go away. "I always tell my patients that I love a false alarm," says Dr. Puritz. "I'm happy to see you and say you're fine rather than miss something where I could have intervened."

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