Diarrhea during the second trimester is relatively common and usually not a cause for concern. About 9% of pregnant women experience diarrhea at some point during pregnancy, compared to less than 2% of women before pregnancy. While constipation gets most of the attention as a pregnancy digestive complaint, loose stools are a real and recognized part of the experience for many women.
Why Pregnancy Changes Your Digestion
Rising progesterone levels are the main driver of digestive changes throughout pregnancy. Progesterone relaxes smooth muscle tissue, including the muscles lining your intestines. This slows down the pace at which food moves through your digestive tract, which is why constipation is the more talked-about problem. But a slower gut doesn’t always mean firmer stools. The same hormonal shifts that slow transit can also make your system more reactive to foods, supplements, or minor irritants that wouldn’t have bothered you before.
By the second trimester, your uterus is growing rapidly and starting to crowd the space your intestines normally occupy. This physical pressure can change how your bowels function from day to day. Some women alternate between constipation and diarrhea as their body adjusts to the shifting landscape inside their abdomen.
Common Second Trimester Triggers
Diet changes are one of the most frequent causes. Many women overhaul their eating habits once they’re past the nausea of the first trimester, adding more fruits, vegetables, and fiber. A sudden increase in fiber or new foods your body isn’t used to can loosen stools. Dairy sensitivity can also emerge or worsen during pregnancy, leading to bloating and diarrhea after meals that previously felt fine.
Prenatal vitamins are often blamed for digestive trouble, but the evidence is more nuanced than you might expect. A controlled trial comparing iron supplements (50 mg daily) to placebo in pregnant women found no significant difference in diarrhea rates between the two groups at either 24 to 28 weeks or 32 to 36 weeks. Research suggests that iron supplements up to 80 mg per day don’t reliably cause gastrointestinal side effects. That said, if you notice a pattern where your symptoms line up with when you take your prenatal, it’s worth trying a different brand or taking it with food.
Stress and anxiety, which can spike during the second trimester as the reality of parenthood settles in, also play a role. Your gut and brain communicate constantly, and emotional stress can speed up intestinal contractions.
When Diarrhea Signals Something Else
Most second trimester diarrhea is short-lived and harmless. The American College of Obstetricians and Gynecologists recommends contacting your healthcare provider if diarrhea lasts more than two days, or sooner if you notice any of the following: blood or pus in your stool, fever, severe abdominal pain, or signs of dehydration like dark urine, dizziness, dry mouth, or infrequent urination.
Foodborne illness is a particular concern during pregnancy because your immune system is naturally suppressed. Listeriosis, caused by contaminated food, can produce diarrhea along with fever, muscle aches, nausea, and headache. Symptoms can take days or even weeks to appear after exposure. The FDA notes that pregnant women may feel only mildly ill or not sick at all, but listeriosis can lead to miscarriage, preterm birth, or serious health problems for the baby. If diarrhea comes with a fever, don’t wait it out.
Diarrhea is also listed as a possible sign of preterm labor, alongside lower abdominal cramping, pelvic pressure, back pain, and contractions. This doesn’t mean every bout of loose stools is a warning sign. But if diarrhea comes with rhythmic cramping, a feeling of pressure low in your pelvis, or a persistent backache that feels different from your usual discomfort, those symptoms together deserve prompt attention.
Staying Hydrated Matters More Than Usual
Your body uses water to maintain the placenta and amniotic fluid surrounding your baby. Diarrhea pulls fluid out of your system faster than normal, so dehydration can develop quickly. Early signs include a dry or sticky mouth, sleepiness, thirst, headache, and darker urine. More severe dehydration can cause a rapid heartbeat, low blood pressure, extreme thirst, and very little urine output.
Low fluid intake during pregnancy has been linked to reduced amniotic fluid levels. If you’re dealing with loose stools, prioritize water, clear broths, and drinks with electrolytes. Small, frequent sips work better than trying to drink large amounts at once when your stomach is already unsettled.
Managing Diarrhea at Home
Bland, low-fiber foods can help calm your digestive system while you recover. Bananas, white rice, applesauce, and plain toast are gentle on the gut and easy to tolerate. These foods won’t cure diarrhea, but they provide calories and nutrients without further irritating your intestines. Once your stools firm up, gradually reintroduce your normal diet rather than jumping straight back to high-fiber meals.
Avoiding known triggers helps too. Greasy or fried foods, caffeine, high-sugar drinks, and dairy (if you suspect sensitivity) can all worsen loose stools. Eating smaller, more frequent meals instead of three large ones gives your digestive system less to process at once.
For over-the-counter options, loperamide (Imodium) is generally considered the only pregnancy-safe anti-diarrheal medication. However, Cleveland Clinic notes it should not be used during the first trimester and should not be taken for more than 24 hours. If your symptoms persist beyond that window, the next step is calling your provider rather than continuing to self-treat.