Loose stools, defined as three or more watery or unformed bowel movements in a day, are a frequent occurrence as the body prepares for birth in the final weeks of pregnancy. While this digestive change signals the body is nearing the end of pregnancy, it is a non-specific symptom, meaning it is not a definite indicator of active labor. Understanding the physiological processes helps clarify why this change happens and what it truly signifies.
Why Digestion Changes Before Labor
The body’s preparation for labor involves releasing hormones that affect smooth muscle tissue throughout the body, including the digestive tract. Prostaglandins are the primary hormones involved, playing a role in softening the cervix and stimulating uterine contractions. These compounds act as local mediators of uterine activity because prostaglandin receptors are present in the myometrial tissue, the muscle layer of the uterus.
Prostaglandins also affect the smooth muscles lining the intestines. As hormone levels rise to prepare the reproductive organs for birth, they simultaneously stimulate the muscles of the bowel, increasing their movement. This increased motility, or speed of movement, means waste material passes through the intestines more quickly than usual, resulting in a reduced absorption of water.
This process naturally leads to the production of softer, looser stools. The digestive system essentially begins a clearing-out process, which often occurs hours or days before true labor contractions begin. Loose stools are best understood as an early sign of the body preparing for delivery, rather than an indication that active labor has officially started.
Other Reasons for Loose Stools in Late Pregnancy
Not every instance of loose stools in the third trimester is solely due to impending labor, as many other factors can cause temporary digestive upset. Changes in diet are a frequent cause, especially increased fiber intake or sudden dietary modifications. Some individuals find that prenatal vitamins can also cause stomach irritation or loose stools.
Additionally, the immune system is naturally suppressed during pregnancy, increasing susceptibility to viral or bacterial infections like gastroenteritis, which cause diarrhea regardless of pregnancy status. Psychological factors like anxiety and stress, common in late pregnancy, can also stimulate bowel contractions, leading to looser movements. Differentiating between these external causes and hormonal shifts requires observing other accompanying symptoms.
Reliable Signs That Labor Has Begun
Because loose stools are an ambiguous symptom, recognizing the definitive signs of labor is necessary before contacting a healthcare provider. The most reliable indicators involve changes in uterine activity and cervical state. True contractions follow a regular pattern, increasing in intensity, duration, and frequency over time. Unlike practice contractions, true labor contractions will not ease or stop when position or activity changes.
Another clear sign is the rupture of membranes, commonly known as the “water breaking.” This may manifest as a sudden gush or a slow trickle of fluid that cannot be controlled, and the fluid should be clear or pale. The passing of the “bloody show” is also a reliable indicator, occurring when the mucus plug that sealed the cervix dislodges. This discharge is typically sticky, jelly-like mucus that is pink or blood-tinged as the cervix begins to soften and open.
While the loss of the mucus plug suggests that delivery is approaching, it can happen days or even weeks before labor begins. The combination of regularly timed, progressively stronger contractions, along with the rupture of membranes or a bloody show, provides the clearest evidence that active labor is underway.
When to Contact Your Doctor About Diarrhea
Even when loose stools relate to labor preparation, they become a medical concern if they lead to dehydration. Prolonged diarrhea that lasts more than 48 hours requires medical attention, regardless of whether labor has started. Dehydration poses a risk during pregnancy; symptoms include a dry mouth, dark yellow urine, dizziness, and decreased urine output.
Several red flag symptoms warrant an immediate call to a healthcare provider, including a high fever, severe abdominal pain, or stools containing blood or pus. If you notice diarrhea combined with signs of preterm labor, such as regular, frequent contractions before 37 weeks of gestation, contact your care team urgently. Staying well-hydrated with water and electrolyte-rich fluids is the most important self-management step while awaiting medical guidance.