Cramping during pregnancy is often scary, but it's a common symptom through all trimesters and most are not dangerous. So it can be helpful to know that cramping is the uterus's response to just about anything that is happening to it. "The uterus is a muscle," says Holly Puritz, M.D., medical director for Sentara Lee Hospital Group for Women in Norfolk, Virginia, "and the only thing a muscle knows how to do is contract, and a contraction feels like a cramp."
That means that any time 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 your cramping is a concern and when it's no big deal.
Things that can cause your uterus to contract or cramp at any time during pregnancy include a full bladder, an orgasm, exercise, or a urinary tract infection. Trimester by trimester, here's what you can expect:
For some women, cramping is the first sign that they are pregnant, as it's common to experience cramping when a fertilized egg makes its home in the uterine wall. This is called implantation cramping, and it can feel like your period is about to start, says Dr. Puritz. The rapid uterine growth in the first two trimesters of pregnancy can also lead to cramping, says Chad Klauser, M.D., clinical assistant professor of obstetrics and gynecology at the Mount Sinai School of Medicine in New York City. Plus, changing hormone levels can lead to increased gas, bloating, and constipation. "The majority of pregnancies will have some mild (light) cramping intermittently during the first 16 weeks," Dr. Klauser says.
Miscarriages often happen when there is abnormal development in an egg or embryo (usually caused by chromosomal abnormalities) and the body responds by eliminating the pregnancy. The cramping associated with miscarriage is actually caused when blood and tissue leaving the uterus irritates it, causing it to contract.
The middle trimester of pregnancy may be the time when you're least likely to experience cramping or other uncomfortable pregnancy symptoms. One exception is with women who are pregnant with multiples, since the uterus grows more rapidly and will reach third-trimester proportions in the second trimester. (This is one reason women carrying multiples are at greater risk for preterm labor.)
Another common exception is round ligament pain, which occurs around week 13 when the ligaments that support the uterus are stretched as the uterus grows upward. This kind of benign pain is usually quick, sharp one-sided pain. Mild urinary tract infections can also cause cramping in a pregnancy.
A more serious, but rare, cause of cramping in the second trimester is uterine fibroids. These harmless overgrowths of tissue (which are more common in African American women) can start to break down in the second trimester, because there is not enough blood to sustain their growth. When they do, the pain is severe and almost always happen between 15 and 18 weeks of pregnancy. Any woman who has a history of uterine fibroids should be alert to cramping at this stage of pregnancy, because she may need hospitalization to manage the pain effectively until it passes.
It is very common for women who are in their third trimester and almost to term to experience cramping which is often in the form of those famous Braxton Hicks contractions. These are the same contractions that you will experience when labor begins, but the difference is that they will not progress into labor. Of course, when cramping occurs in the third trimester or even in the second, it's important to determine whether you could be experiencing preterm labor. Make sure that the doctor checks your cervix to see if it has dilated, which can be a sign of early labor. If it's not early labor, drinking a couple of glasses of water or juice and resting should help quiet your pregnancy cramps. However, if it persists, let your doctor know.
You've had sex. That's the first question Dr. Puritz asks her patients when they call. "Intercourse is one of the most common causes of cramping," she says. That's because semen contains prostaglandins that stimulate the uterus. "It's fine to have sex," says Dr. Puritz, "but sometimes you'll feel some pretty strong contractions. So, if the answer is 'yes' to having sex, then I will almost always say 'Okay, I'm not worried about it. Get off your feet and get hydrated.'"
Changing position makes them better or worse. This is generally a sign that what you're experiencing is related to stretching of the uterus or its supporting ligaments.
A bowel movement or passing gas brings relief. This means the pain is more likely related to a gastrointestinal problem rather than to the uterus, says Dr. Klauser.
Six or more contractions in an hour, which could be a sign of preterm labor.
Dizziness, lightheadedness, or bleeding that accompanies cramping (especially if you have not yet confirmed your pregnancy with an ultrasound). This can 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.
Pink discharge is a serious sign of preterm labor, because it can mean your cervical length is changing.
Back or abdominal pain that's intense and associated with nausea, vomiting, and/or fever. Back cramping and/or pain in your abdomen area could be symptoms of appendicitis, kidney stones, or gallbladder disease.
Your pain is not improving over time or with changes in your physical position.
The first advice Dr. Puritz gives her patients is to get off their feet, rest, drink fluids, and take acetaminophen (Tylenol) if they need it for pain relief. Don't use a heating pad on your abdomen—raising your core temperature is dangerous during pregnancy, especially in the first trimester. (Using one on your extremities is fine, Dr. Puritz says.)
Dr. Klauser recommends that his patients try a warm shower and taking stretching and sitting breaks throughout the day, particularly if their cramping is worse after long periods of being in one position.
You should always feel free to contact your doctor with your cramping concerns. "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."