Experiencing a shift in bowel habits, including more frequent movements or mild diarrhea, is a common symptom during the final stage of pregnancy. This change in the third trimester is a physiological response as your body prepares for childbirth. Multiple factors contribute to this digestive acceleration, ranging from the mechanical impact of the growing baby to a surge in labor-related hormones. Understanding these causes can help normalize this late-pregnancy development.
Hormonal Shifts Affecting Digestion
The change in bowel activity is partly governed by hormones that fluctuate significantly as the due date approaches. Prostaglandins, a group of lipid compounds with diverse hormone-like effects, play a major role in this digestive acceleration. These compounds soften the cervix in preparation for labor, but they also stimulate smooth muscle tissue throughout the body, including the intestines.
This stimulation increases the movement of the digestive tract, known as peristalsis, resulting in faster transit time and more frequent stools. While progesterone often causes constipation earlier in gestation, its effects are sometimes overridden or diminished by these later-stage hormonal signals. The body’s preparation for labor involves widespread muscular changes, and the digestive system is affected by this process.
Physical Pressure from the Growing Uterus
The size and weight of the uterus in the third trimester exert a direct, mechanical influence on the intestines and colon. As the baby grows, the abdominal cavity becomes crowded, physically compressing the lower digestive organs. This compression can push fecal matter through the colon more quickly than usual.
The baby will often “drop” or engage deeper into the pelvis, a process known as lightening, which occurs before delivery. While lightening can relieve pressure on the diaphragm and lungs, it often increases pressure downward onto the pelvic floor and lower bowels. This shift in positioning may intensify the feeling of urgency and lead to more frequent trips to the bathroom.
Bowel Movements as a Sign of Impending Labor
An increase in bowel movements or the onset of diarrhea can be one of the earliest, non-contraction signs that labor is imminent. The body naturally initiates a “clearing out” process that often precedes the start of active labor. This physiological mechanism empties the digestive tract to make room for the baby’s descent and reduces the risk of bowel contents being expelled during pushing.
The surge of hormones that trigger uterine contractions also affects the bowel. The body releases higher levels of prostaglandins and oxytocin in the hours or days before labor begins. These compounds stimulate the muscles of the large intestine, leading to increased motility and sometimes presenting as loose stools or mild diarrhea. This natural laxative effect is a normal part of the preparation phase for childbirth.
The timing of this symptom is variable; it can happen days or weeks before true labor begins. It is often noticed alongside other pre-labor signs like the loss of the mucus plug or increasing intensity of Braxton Hicks contractions. If you notice a sudden change in stool consistency accompanied by other early labor signs, it indicates your body is preparing for delivery.
When Increased Frequency Becomes a Medical Concern
While increased or loose bowel movements are a normal part of late pregnancy, certain symptoms warrant immediate attention from a healthcare provider. The primary concern with diarrhea or frequent stools is the risk of dehydration, which can be taxing on the pregnant body. Signs of dehydration include dark-colored urine, a dry mouth, and severe thirst.
If the increased frequency is accompanied by a fever or intense abdominal pain, it could signal an infection or other complication requiring medical evaluation. Contact your doctor if you notice any blood or excessive mucus in the stool, or if the diarrhea lasts for more than 48 hours. Monitoring these symptoms ensures that a normal physiological change is not masking a more serious issue.