Diarrhea before labor

By trimester

Weeks 1–13

1st trimester

Loose stools this early are almost never related to labor, since labor is far off. They're more likely tied to diet, a stomach bug, or ordinary first-trimester digestive changes, so mention persistent diarrhea to your provider the same way you would at any other time.

Weeks 14–27

2nd trimester

Diarrhea in the second trimester isn't a labor sign either. Handle it like any other digestive symptom: track how long it lasts, stay hydrated, and call your provider if it doesn't improve within a couple of days or comes with fever.

Weeks 28–birth

3rd trimester

This is when diarrhea gets reframed as a possible prelabor sign, especially in the final week or two alongside other changes like losing the mucus plug or a sudden burst of energy. It doesn't predict timing precisely, and it's just as often an ordinary stomach bug, so watch for fever, bloody stool, or signs of dehydration.

What does the evidence show for diarrhea before labor?

• Prostaglandins, the same signaling molecules that soften and ripen the cervix before labor, are also a documented, direct cause of diarrhea, with close to two in five patients reporting it after certain prostaglandin E2 dosing. 1
• Clinicians describe a cluster of premonitory signs in the days before true labor, including loss of the mucus plug, bloody show, and lightening as the baby's head settles into the pelvis, all tied to the same cervical and hormonal shifts that can loosen stools. 2
• Bowel habits shift broadly in the third trimester on their own: one study found two-thirds of pregnant women reported a change in stool consistency and about 41% reported new urgency, driven by both hormonal and mechanical changes. 3
• Diarrhea pulls fluids and electrolytes out of the body faster than solid stool does, and pregnant people are specifically named as more likely to have health problems from diarrhea and should stay in touch with their provider about it. 4
• Watery diarrhea with fever, or stool that's bloody or black and tarry, points toward a stomach virus rather than ordinary prelabor loosening, and pregnant people are told to see a doctor right away for symptoms like these. 5

When should I call my provider about diarrhea before labor?

Fever, chills, or stool that's bloody, black and tarry, or watery and frequent points toward a stomach virus or another infection rather than ordinary prelabor loosening, and pregnant people are specifically advised to see a doctor right away for these signs. Diarrhea paired with vomiting raises the risk of dehydration quickly, which is worth calling your provider about the same day, especially if you feel dizzy, can't keep fluids down, or notice a racing heartbeat. Diarrhea alongside regular, strengthening contractions, a gush or trickle of fluid, or heavy bleeding is less about the diarrhea itself and more about labor or another obstetric issue that needs prompt evaluation. None of these lists replace your own judgment: if this symptom worries you, that on its own is enough reason to check in with your healthcare provider.