Stomach cramps in women can stem from the reproductive system, the digestive system, or both, and hormonal fluctuations often blur the line between the two. Roughly 71% of women worldwide experience menstrual cramping alone, making it the single most common cause. But period pain is far from the only explanation. Understanding where your cramps fall in your cycle, how they relate to bowel habits, and what other symptoms accompany them can help you narrow down what’s going on.
Menstrual Cramps and Prostaglandins
The most frequent cause of lower abdominal cramping in women is the menstrual period itself. During menstruation, the uterus contracts to shed its lining, and those contractions are driven by hormone-like substances called prostaglandins that trigger both pain and inflammation. Women who produce higher levels of prostaglandins tend to have more intense cramps. The pain typically starts one to two days before bleeding begins, peaks on the first or second day of the period, and fades within 48 to 72 hours.
This type of cramping, called primary dysmenorrhea, is not caused by an underlying disease. It feels like a dull, throbbing ache centered low in the abdomen, sometimes radiating into the lower back and thighs. Nausea, loose stools, and fatigue often come along for the ride, partly because prostaglandins also act on the gut.
Ovulation Pain
Some women feel a sharp or cramp-like pain on one side of the lower abdomen roughly two weeks before their next period, right around the time an egg is released. This mid-cycle pain happens when the fluid-filled sac surrounding the egg stretches and eventually ruptures to release it. The discomfort can last anywhere from a few minutes to a couple of days and typically alternates sides from month to month, since each ovary takes turns releasing an egg. It’s harmless, but if you aren’t tracking your cycle, it can be confusing because it doesn’t line up with your period at all.
Endometriosis
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, attaching to the ovaries, fallopian tubes, bowel, or other pelvic structures. Over time, this tissue forms cysts, adhesions, and scar tissue that cause progressively worsening pain. Symptoms include very painful menstrual cramps, pain between periods, pain during sex, heavy or irregular bleeding, and bowel issues like diarrhea, constipation, or bloating.
One hallmark of endometriosis is that the pain is usually cyclical, flaring before and during menstruation as hormonal changes increase inflammation in the misplaced tissue. Some women, though, experience constant pain that doesn’t follow any pattern. The condition can only be definitively confirmed through a minimally invasive surgical procedure where a small camera is used to visualize and biopsy the tissue. If your period cramps have been getting worse over the years, or if over-the-counter pain relief no longer touches them, endometriosis is worth investigating.
Irritable Bowel Syndrome and Hormones
IBS affects the large intestine and causes cramping, bloating, gas, and changes in bowel habits. It’s more common in women than men, and there’s a clear hormonal connection. Estrogen and progesterone receptors exist on cells throughout the gastrointestinal tract, meaning the gut is literally built to respond to reproductive hormones. Research from the UNC Center for Functional GI Disorders found that 50% of women with IBS report worsening bowel symptoms during menstruation, compared to 34% of women without IBS.
The pattern is telling: stomach pain, diarrhea, nausea, and bloating tend to be worst during the period, when estrogen and progesterone drop to their lowest levels. Bloating specifically can also worsen in the second half of the cycle, before menstruation begins. After menopause, when hormone fluctuations stop, IBS symptoms often decline, reinforcing the hormonal link. Women with IBS also show heightened pain sensitivity in the gut during menstruation, meaning the intestines physically overreact to normal stretching and movement.
A practical way to tell IBS cramps from reproductive cramps: IBS pain is closely tied to bowel movements. It may ease or worsen after you go, and it tends to appear several times a week over months rather than only around your period.
Ovarian Cysts
Small, fluid-filled cysts form on the ovaries regularly as part of normal ovulation, and most dissolve on their own without ever causing symptoms. Problems start when a cyst grows large, twists, or ruptures. A ruptured ovarian cyst typically causes sudden, sharp pain in the lower belly or back, along with bloating and sometimes vaginal spotting. Most women feel significant pain at the moment of rupture that eases over the following days.
A more serious complication is ovarian torsion, where the weight of a cyst causes the ovary to twist on itself, cutting off its blood supply. This produces severe, sudden pain often accompanied by nausea and vomiting, and it requires emergency treatment. Cysts related to endometriosis (called endometriomas) can fill with blood and grow large enough to cause persistent pelvic pain even without rupturing. During the first trimester of pregnancy, a functional cyst called a corpus luteum normally forms to produce hormones that sustain the pregnancy; it typically disappears by the second trimester.
Pelvic Inflammatory Disease
PID is an infection of the reproductive organs, most often caused by sexually transmitted bacteria like chlamydia or gonorrhea, though other infections can trigger it too. It causes pain in the lower abdomen that may be dull and constant or sharp and crampy, along with unusual discharge, fever, and pain during sex or urination. PID can be tricky because many women have only mild symptoms or none at all, which means the infection can quietly damage the fallopian tubes and surrounding tissue if left untreated. Infected ovarian cysts can also develop in the setting of PID, and if one of those cysts ruptures, it can lead to a dangerous widespread infection.
Ectopic Pregnancy
An ectopic pregnancy happens when a fertilized egg implants outside the uterus, most commonly in a fallopian tube. Early on, it may feel like a normal pregnancy: missed period, breast tenderness, nausea. As the egg grows in the wrong location, the first warning signs are usually pelvic pain and light vaginal bleeding. If blood leaks from the fallopian tube, you may feel shoulder pain or pressure in the rectum. A growing ectopic pregnancy can eventually rupture the tube, causing heavy internal bleeding, extreme lightheadedness, fainting, and shock. This is a life-threatening emergency. Any combination of sharp pelvic pain, vaginal bleeding, and dizziness in a woman of reproductive age warrants immediate medical attention.
How to Tell Reproductive Pain From Digestive Pain
The overlap between these two categories confuses even experienced clinicians, but a few patterns can help you sort out what you’re dealing with. Cramps that arrive on a predictable schedule tied to your menstrual cycle point toward a reproductive cause, whether that’s normal period pain, endometriosis, or ovulation. Cramps that correlate with eating, change with bowel movements, or show up multiple times a week regardless of where you are in your cycle lean toward a digestive cause like IBS.
The complication is that hormones affect both systems simultaneously. Prostaglandins released during your period can speed up the bowel, causing diarrhea and gut cramps right alongside uterine cramps. Women with endometriosis often develop bowel symptoms that mimic IBS. If your symptoms don’t fit neatly into one box, tracking them alongside your cycle for two or three months creates a pattern that’s far more informative than any single episode.
Warning Signs That Need Emergency Care
Most stomach cramps in women, even painful ones, resolve on their own or with standard treatment. But certain combinations of symptoms signal something that can’t wait. Seek emergency care for sharp, sudden pelvic pain accompanied by heavy vaginal bleeding, fever, nausea and vomiting severe enough to prevent keeping fluids down, or signs of shock like fainting, dizziness, or a rapid pulse. These can indicate a ruptured ectopic pregnancy, ovarian torsion, a ruptured infected cyst, or appendicitis.