The final weeks of pregnancy often bring heightened awareness to every new ache, cramp, or change in bodily function. Among the many symptoms that cause expectant parents to wonder if labor is beginning, a sudden onset of diarrhea is common. This digestive change near the end of the third trimester can be a source of confusion, as it is difficult to determine if it is simply a stomach upset or a signal that childbirth is imminent. Understanding the underlying mechanisms and knowing what signs to look for can help clarify this late-pregnancy experience.
Diarrhea as a Precursor to Labor
Diarrhea can be an indication that the body is preparing for labor, though it is not a universal sign. This digestive shift is often called “prelabor diarrhea” when it occurs close to the estimated due date. The timing varies widely, but for those who experience it, loose stools may begin anywhere from a few days to a few hours before contractions start in earnest.
The body may be naturally clearing the digestive tract in preparation for the physical exertion of delivery. This clearing mechanism may create more space in the pelvis for the baby to descend and move through the birth canal. While it suggests labor is near, this symptom alone is not as reliable as other labor signs, such as regular, intensifying contractions or the loss of the mucus plug.
The Hormonal Mechanism
The physiological reason behind this prelabor symptom is rooted in the powerful hormonal changes that initiate birth. The body begins to release an increased amount of chemical messengers called prostaglandins. Prostaglandins are best known for their role in effacing the cervix to prepare it for dilation.
These hormone-like substances affect smooth muscle tissue throughout the body, not just the uterus and cervix. The gastrointestinal tract is lined with smooth muscle, and the surge in prostaglandins increases the motility of the bowels. This increased rate of muscle contraction and movement in the intestines leads directly to loose, frequent, and sometimes urgent stools. The effects of prostaglandins on the gut are so pronounced that synthetic versions of the hormone are known to cause gastrointestinal side effects when used to medically induce labor.
Differentiating Causes
It is important for expectant parents to distinguish between labor-related diarrhea and digestive issues caused by other factors, such as a stomach virus or food poisoning. Labor-related diarrhea is typically not accompanied by systemic signs of infection, usually presenting without a high fever or persistent, severe vomiting. The abdominal cramping felt is often the result of the bowel activity itself, which can be difficult to distinguish from early labor contractions.
A key differentiating factor is the presence of other labor indicators, like the start of rhythmic contractions that increase in frequency and intensity. Symptoms that point toward an infection include blood or mucus in the stool, prolonged diarrhea lasting more than 48 hours, or sharp, localized abdominal pain. If diarrhea is paired with these more alarming symptoms, another cause may be involved that requires medical attention.
Hydration and Medical Guidelines
Regardless of the cause, managing diarrhea in late pregnancy requires a primary focus on preventing dehydration. Losing significant fluids can be dangerous, as it can sometimes lead to an increase in uterine irritability or contractions. Expectant parents should increase their fluid intake immediately, focusing on water and electrolyte-rich beverages like sports drinks or oral rehydration solutions.
Contact a healthcare provider if there are any signs of severe dehydration, such as dry mouth, dizziness, or significantly decreased urination. Medical consultation is also warranted if the diarrhea lasts longer than two days, or if it is accompanied by a high fever, severe pain, or any visible blood in the stool.