Constipation affects 37% of pregnant women, with rates highest in the first trimester at 56%, according to a cross-sectional study of 381 pregnant women reviewed by Gram Research. Women who consumed more dietary fiber and fluids had significantly lower constipation rates, with each additional gram of fiber reducing constipation odds by 12%. While physical activity is healthy during pregnancy, it didn’t independently prevent constipation after accounting for diet and other factors.
Constipation affects more than one-third of pregnant women, especially in early pregnancy, according to Gram Research analysis of a study of 381 pregnant women in Iran. Researchers found that eating more fiber and drinking more water significantly reduced constipation problems, while exercise didn’t make as much difference as expected. The study shows that simple dietary changes—like adding fruits, vegetables, and staying hydrated—may help pregnant women feel more comfortable during pregnancy. However, because this was a snapshot study rather than a long-term follow-up, doctors say more research is needed to confirm these findings.
Key Statistics
A 2026 cross-sectional study of 381 pregnant women found that 37% experienced functional constipation overall, with rates highest in the first trimester at 56%, declining to 29% by the third trimester.
According to research reviewed by Gram, each additional gram of daily dietary fiber intake reduced the odds of constipation by 12% in pregnant women (odds ratio 0.88, 95% CI 0.86-0.91).
A 2026 study of 381 pregnant women in Iran found that higher fluid intake was significantly associated with lower constipation rates, while physical activity did not independently prevent constipation after adjustment for dietary factors.
Women with secondary education had nearly three times higher odds of functional constipation compared to those with higher education levels (odds ratio 2.81), suggesting health literacy may influence constipation risk in pregnancy.
The Quick Take
- What they studied: Whether diet and exercise affect constipation in pregnant women, and how common constipation is at different stages of pregnancy
- Who participated: 381 healthy pregnant women visiting health clinics in Tabriz, Iran, between January 2024 and February 2025. The women were at different stages of pregnancy—some in their first three months, some in the middle, and some near the end.
- Key finding: About 37% of pregnant women experienced constipation overall, but it was most common in the first trimester (56% of women). Women who ate more fiber and drank more water had significantly lower rates of constipation. Interestingly, exercise didn’t independently reduce constipation after researchers adjusted for other factors.
- What it means for you: If you’re pregnant and struggling with constipation, increasing fiber and water intake may help more than focusing on exercise alone. However, this study shows a connection, not proof of cause-and-effect, so talk to your doctor about what’s best for your situation.
The Research Details
Researchers collected information from 381 pregnant women at one point in time (called a cross-sectional study). They asked women detailed questions about what they ate using a food frequency questionnaire and how active they were using a standard physical activity survey. They diagnosed constipation using Rome IV criteria, which are medical guidelines that doctors use to identify functional constipation—constipation without an obvious physical blockage.
The women were divided into three groups based on pregnancy stage: first trimester (first three months), second trimester (months four to six), and third trimester (final three months). Researchers then used statistical analysis to see which factors—like diet, exercise, education level, and age—were connected to constipation.
This approach is like taking a photograph of a moment in time rather than filming a movie. It shows what’s happening now but can’t prove that one thing causes another.
Cross-sectional studies are useful for finding patterns and understanding how common a problem is in a population. This design allowed researchers to quickly gather information from many women at different pregnancy stages, showing how constipation changes throughout pregnancy. However, this design has limitations for proving cause-and-effect relationships.
The study used validated, internationally recognized tools (IPAQ for activity, FFQ for diet, and Rome IV criteria for constipation diagnosis), which strengthens reliability. The sample size of 381 women is reasonably large. However, the study was conducted in one city in Iran, so results may not apply equally to all populations. The cross-sectional design means researchers couldn’t follow women over time to see if dietary changes actually prevented constipation. The researchers acknowledged these limitations and called for future long-term studies.
What the Results Show
Constipation affected 37% of all pregnant women in the study, but the rate changed dramatically across pregnancy stages. In the first trimester, 56% of women experienced constipation—more than half. This dropped to 36% in the second trimester and further decreased to 29% in the third trimester. This pattern suggests that constipation is most bothersome early in pregnancy.
Dietary fiber had the strongest protective effect. For every additional gram of fiber women consumed daily, their odds of having constipation decreased by 12% (odds ratio 0.88). Fluid intake showed a similar protective pattern, with higher water consumption associated with lower constipation rates. These findings align with what doctors have long recommended for constipation management.
Education level emerged as an unexpected factor. Women with secondary education (high school level) had nearly three times higher odds of constipation compared to women with higher education levels. Researchers suggest this might reflect differences in health knowledge or access to dietary information, though the exact reason isn’t clear from this study.
Physical activity, which many people assume helps constipation, did not show an independent association with constipation after researchers adjusted for other factors like diet and education. This was surprising because exercise is commonly recommended for constipation relief. Age and other demographic characteristics also weren’t independently associated with constipation in the final analysis. These findings suggest that dietary factors may be more important than activity level for preventing pregnancy-related constipation.
Previous research on constipation in pregnancy has shown mixed results, which is why this study was needed. This research confirms what many smaller studies suggested—that fiber and fluid intake matter—but provides clearer evidence with a larger sample. The finding that physical activity doesn’t independently prevent constipation contradicts some earlier assumptions, suggesting that diet may be the primary modifiable factor.
The biggest limitation is the cross-sectional design. Because researchers collected all information at one time point, they cannot prove that eating more fiber actually causes less constipation—only that these factors are associated. Women’s dietary and activity recall may be inaccurate since they reported from memory. The study was conducted in one Iranian city, so findings may not apply to pregnant women in other countries with different diets and healthcare systems. Additionally, the study didn’t account for medications or supplements pregnant women might be taking, which could affect constipation. The researchers themselves noted that prospective longitudinal studies are needed to confirm causality.
The Bottom Line
Pregnant women experiencing constipation should prioritize increasing dietary fiber intake through fruits, vegetables, whole grains, and legumes, and ensure adequate fluid intake (especially water). This recommendation has strong support from this research. While exercise is beneficial for overall pregnancy health, it may not specifically prevent constipation. Women should discuss constipation concerns with their healthcare provider, as individual needs vary. Those with secondary education or limited health literacy may benefit from targeted nutritional counseling.
All pregnant women should be aware of these findings, particularly those in their first trimester when constipation is most common. Women experiencing constipation should prioritize dietary changes before assuming they need medication. Healthcare providers should emphasize dietary fiber and fluid intake in pregnancy counseling. This research is less relevant to non-pregnant individuals, though the general principles about fiber and hydration apply broadly.
Dietary changes typically show effects on constipation within days to one week, though individual responses vary. Women should expect gradual improvement rather than immediate relief. Consistency matters—maintaining higher fiber and fluid intake throughout pregnancy appears most beneficial based on this research.
Frequently Asked Questions
Is constipation normal during pregnancy and how common is it?
Constipation affects about 37% of pregnant women, making it a common pregnancy complaint. It’s most prevalent in the first trimester, affecting 56% of women, then decreases as pregnancy progresses. While normal, it can significantly impact comfort and quality of life.
What should I eat to prevent constipation during pregnancy?
Increase dietary fiber through fruits, vegetables, whole grains, and legumes. Research shows each additional gram of daily fiber reduces constipation odds by 12%. Pair this with adequate fluid intake—aim for 8-10 glasses of water daily. Start increases gradually to avoid bloating.
Does exercise help with pregnancy constipation?
While exercise benefits overall pregnancy health, this study found it didn’t independently prevent constipation after accounting for diet. Dietary fiber and fluid intake appear more directly protective against pregnancy-related constipation than physical activity alone.
When is constipation most likely during pregnancy?
Constipation is most common in the first trimester, affecting 56% of pregnant women, compared to 36% in the second trimester and 29% in the third trimester. If you’re struggling early in pregnancy, dietary adjustments may provide relief.
Can I take fiber supplements instead of eating high-fiber foods?
This study measured dietary fiber from food sources. While fiber supplements may help, whole foods provide additional nutrients and hydration benefits. Discuss supplement use with your healthcare provider, as individual pregnancy needs vary and some supplements require medical approval.
Want to Apply This Research?
- Log daily fiber intake (target: 25-30 grams for pregnant women) and water consumption (target: 8-10 glasses daily), then track constipation frequency weekly to identify patterns and measure improvement over time.
- Set daily reminders to drink water at regular intervals and add one high-fiber food to each meal. Start with small increases to avoid bloating, gradually building to recommended levels while monitoring constipation symptoms.
- Create a weekly constipation symptom score (1-10 scale) and correlate it with fiber and water intake logs. Review trends monthly to identify which dietary adjustments work best for your individual pregnancy.
This research shows an association between dietary factors and constipation in pregnancy but does not prove cause-and-effect. Pregnant women should consult their healthcare provider before making significant dietary changes or starting supplements, as individual needs vary based on medical history, medications, and pregnancy complications. This information is not a substitute for professional medical advice. If you experience severe constipation, abdominal pain, or other concerning symptoms during pregnancy, contact your healthcare provider immediately.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.