Painful bowel movements during pregnancy are extremely common, and the causes stack on top of each other. Rising progesterone slows your digestive system, the growing uterus presses on your rectum, iron supplements harden your stool, and all of that straining can lead to hemorrhoids or small tears. About 40% of pregnant women develop hemorrhoids or anal fissures, most often in the third trimester.
Progesterone Slows Your Entire Digestive System
The biggest driver is progesterone, the hormone that rises steadily throughout pregnancy to support the uterus. Progesterone also relaxes smooth muscle everywhere in your body, including the walls of your intestines. It does this by triggering the release of nitric oxide inside the muscle cells, which flips the chemistry toward relaxation and away from the rhythmic contractions that normally push food through your gut.
The result is slower transit time. Food and waste sit in the colon longer, and the longer stool stays there, the more water your body absorbs from it. That leaves you with hard, dry, difficult-to-pass stool. This effect begins in the first trimester and intensifies as progesterone levels climb, which is why many women notice constipation getting progressively worse as pregnancy continues.
Your Uterus Physically Compresses the Rectum
By the third trimester, the uterus has grown large enough to press directly on the rectum and lower colon. This physical compression narrows the passage stool has to travel through, making evacuation harder and sometimes painful even when the stool itself isn’t especially hard. The weight of the uterus also puts stress on the pelvic floor muscles, which play a key role in coordinating bowel movements. When those muscles are strained or fatigued, they don’t relax properly during a bowel movement, forcing you to push harder and creating a cycle of straining, pain, and further pelvic floor weakening.
Hemorrhoids and Anal Fissures
Hemorrhoids are swollen blood vessels around the anus, and anal fissures are tiny tears in the lining of the anal canal. Together, they affect roughly 44% of pregnant and postpartum women. The third trimester is when they’re most likely to appear, accounting for about 61% of cases. Both conditions make bowel movements actively painful rather than just uncomfortable.
Hemorrhoids during pregnancy develop because increased blood volume and pressure from the uterus cause veins around the rectum to swell. Straining against hard stool makes them worse. Symptoms include pain, itching, burning, and sometimes bright red bleeding on the toilet paper. In more severe cases, a blood clot can form inside a hemorrhoid (thrombosis), causing intense, sudden pain and a firm lump near the anus.
Anal fissures happen when hard stool stretches the anal lining beyond its limit. The pain is typically sharp and burning during the bowel movement itself, sometimes lasting minutes to hours afterward. Once a fissure forms, each subsequent bowel movement reopens it, which is why the pain can feel like it never fully goes away.
Iron in Prenatal Vitamins Makes It Worse
Prenatal vitamins contain iron to support the dramatic increase in blood volume during pregnancy, but iron is notorious for causing constipation. In clinical studies, roughly 21 to 23% of pregnant women taking prenatal multivitamins reported constipation as a side effect. Interestingly, the specific type or dose of iron doesn’t seem to make much difference. Whether the supplement contained 35 mg or 60 mg, the rates of digestive side effects were similar.
Iron constipation compounds the hormonal constipation that’s already happening. If you’re noticing that your stool became noticeably harder or darker after starting prenatal vitamins, the iron is likely a contributing factor. Some women find it helps to take their prenatal vitamin with food or at bedtime, though this won’t eliminate the effect entirely.
What Actually Helps
The most effective approach combines fiber, fluids, and movement. Current guidelines recommend about 28 grams of fiber per day during pregnancy, but fewer than 30% of pregnant women actually hit that target. The gap between what’s recommended and what most women eat is significant. Gradually increasing fruits, vegetables, beans, and whole grains can make a noticeable difference in stool consistency within a few days, though adding fiber too quickly can cause gas and bloating.
Hydration matters just as much. The general recommendation is 8 to 10 glasses of water per day during pregnancy, because your body is pulling more water into the bloodstream and amniotic fluid, leaving less for the colon. If you’re not drinking enough, even a high-fiber diet won’t fully soften your stool.
Regular physical activity, even daily walking, helps stimulate intestinal contractions and counteract some of progesterone’s slowing effect. It doesn’t need to be intense. Consistency matters more than duration.
Stool Softeners and Laxatives
When lifestyle changes aren’t enough, several over-the-counter options are considered safe throughout pregnancy. Bulk-forming laxatives (like psyllium) are not absorbed into the bloodstream and carry no known risk of birth defects, making them a first-line option. Stool softeners containing docusate sodium have been studied in multiple trials with no adverse effects on pregnancy. Mineral oil, a lubricant laxative, is poorly absorbed and also appears safe, though it’s typically used short-term.
Stimulant laxatives are generally reserved for when gentler options fail, and it’s worth discussing those with your provider before using them regularly.
Managing Hemorrhoid and Fissure Pain
If the pain is coming from hemorrhoids or fissures rather than constipation alone, softening the stool is still the most important step because it reduces trauma during each bowel movement. Warm sitz baths, where you sit in a few inches of warm water for 10 to 15 minutes, increase blood flow to the area and relax the muscles around the anus. Many women find this provides the most immediate relief.
Topical treatments containing witch hazel or a mild numbing agent can reduce itching and burning. Avoiding sitting on the toilet longer than necessary also helps, since prolonged sitting increases pressure on rectal veins. If you notice a hard, painful lump near the anus or bleeding that doesn’t stop after a day or two, that warrants a call to your provider, as thrombosed hemorrhoids sometimes need to be drained.
Signs That Need Prompt Attention
Most painful bowel movements during pregnancy are caused by constipation, hemorrhoids, or fissures and resolve with the strategies above. But certain symptoms suggest something beyond routine pregnancy-related issues. Persistent rectal bleeding that goes beyond a small streak on the toilet paper, pain in the lower abdomen rather than around the anus, fever, or symptoms that don’t improve after several days of treatment all deserve a conversation with your healthcare provider sooner rather than later.