Diarrhea can happen during pregnancy, but it’s not one of the reliable early signs. Compared to classic indicators like a missed period, nausea, or breast tenderness, loose stools are far less common and far less specific to pregnancy. Only about 9% of pregnant women report diarrhea at any point during pregnancy, and when it does occur, it’s most frequent in the third trimester, not the first few weeks.
That said, hormonal shifts, dietary changes, and prenatal vitamins can all loosen your stools in early pregnancy. So while diarrhea alone shouldn’t make you suspect pregnancy, it’s worth understanding why it happens and what else might be causing it.
Why Pregnancy Affects Your Digestion
Progesterone is the main culprit. This hormone surges after conception to support the pregnancy, but it also relaxes smooth muscle throughout your body, including the muscles lining your digestive tract. The result is slower movement of food through your intestines. Research measuring gut transit times found that food moves through the digestive system significantly faster in the first trimester (about 99 minutes on average) compared to the second and third trimesters (125 and 137 minutes, respectively). After delivery, transit time drops back to around 75 minutes.
This slowdown actually makes constipation the more common pregnancy complaint, affecting roughly 25% of pregnant women, with the highest rates in the first trimester. But hormonal fluctuations don’t affect everyone the same way. Some women’s digestive systems respond to rising progesterone with looser stools rather than firmer ones, especially during the initial hormonal spike in early pregnancy when your body is still adjusting.
Other Pregnancy-Related Causes of Loose Stools
Hormones aren’t the only factor. Several things that change when you become pregnant can independently trigger diarrhea.
Prenatal vitamins are a common one. These supplements list diarrhea, constipation, upset stomach, and belly pain as known side effects. If your loose stools started around the same time you began a prenatal vitamin, the supplement is a likely cause. Switching brands or taking the vitamin with food often helps.
Dietary shifts matter too. Many women overhaul their eating habits after a positive test, adding more fruits, vegetables, and fiber. While that’s generally a good thing, a sudden increase in fiber can cause gas, bloating, and diarrhea until your gut adjusts. New food sensitivities can also emerge during pregnancy. Dairy, caffeine, and artificial sweeteners are common triggers for loose stools even outside of pregnancy, and you may find your tolerance for them changes.
Increased water intake, another common early-pregnancy habit, can also soften stools noticeably if your body isn’t used to the higher volume.
Diarrhea Near Your Due Date
If you’re in your third trimester rather than the first, the context changes. Diarrhea in the final weeks of pregnancy can be an early signal that labor is approaching. As your body prepares for delivery, hormonal shifts (particularly a rise in prostaglandins) can cause your bowels to empty more frequently. This is normal and doesn’t require treatment, though staying hydrated is important heading into labor.
About 13% of women experience diarrhea in the third trimester, making it roughly twice as common as in earlier stages of pregnancy.
How to Tell If Something Else Is Going On
Pregnancy-related diarrhea is typically mild: looser stools than usual without other major symptoms. If your diarrhea comes with fever, vomiting, bloody stools, or severe abdominal cramping, an infection is more likely than a hormonal cause.
Viral gastroenteritis (stomach flu) causes watery diarrhea along with nausea, vomiting, stomach cramps, and sometimes a low-grade fever. Symptoms usually appear one to three days after exposure and resolve within a couple of days, though they can last up to two weeks. Bacterial infections from contaminated food tend to be more severe and may produce bloody diarrhea.
The key distinction: pregnancy-related digestive changes come on gradually and feel like a shift in your normal pattern. An infection hits suddenly and makes you feel sick in multiple ways at once.
Staying Comfortable and Hydrated
For mild diarrhea during pregnancy, hydration is the priority. You lose more water and electrolytes than usual with loose stools, so drinking fluids that contain salt, like sports drinks or broth, helps your body retain what it needs. Plain water alone won’t replace lost sodium.
If diarrhea is persistent or uncomfortable, loperamide (the active ingredient in Imodium) is considered safe during pregnancy but only after the first trimester, and only for short-term use of 24 hours or less. Beyond that, identifying and avoiding trigger foods, like dairy, caffeine, or sugar substitutes, is a better long-term strategy.
Diarrhea paired with a fever of 100.4°F or higher, inability to keep fluids down for more than eight hours, dizziness, or confusion points to dehydration or infection that needs prompt medical attention. Signs of dehydration include dry mouth, dark urine, headaches, and lightheadedness.
The Bottom Line on Diarrhea as a Pregnancy Sign
If you’re wondering whether loose stools mean you might be pregnant, the honest answer is that diarrhea is too nonspecific to tell you much on its own. It has dozens of possible causes, and pregnancy is one of the less common ones. A home pregnancy test, which is accurate from the first day of a missed period, will give you a clear answer far faster than trying to interpret digestive symptoms. If you are pregnant and experiencing diarrhea, it’s almost always manageable with simple hydration and dietary adjustments.