Diarrhea, defined as three or more loose, watery bowel movements in a day, is a common and often startling change in bowel habits at 37 weeks of pregnancy. This point marks the beginning of the “early term,” meaning the baby is considered full-term and could arrive at any time. Many expectant parents wonder if this digestive change signals the immediate onset of labor. While frequently a normal part of the body’s final preparations for delivery, it can also be traced to non-labor-related factors specific to late pregnancy. Understanding the potential causes and management strategies provides reassurance during this final stage of the journey.
Is This a Sign of Labor?
The appearance of diarrhea in the days or hours leading up to labor is often due to a physiological mechanism preparing the body for childbirth. As delivery nears, the body releases prostaglandins, hormones that primarily soften and thin the cervix (effacement) to allow labor progression.
These hormones also affect the smooth muscles in the gastrointestinal tract. Stimulation leads to increased motility, causing a “cleansing” effect as the body attempts to empty the bowels. This natural process results in the looser, more frequent stools observed just before labor begins.
While diarrhea can be an indication that labor is imminent, sometimes occurring 24 to 48 hours before active contractions start, it is rarely the sole indicator. The hormonal surge is usually accompanied by other signs of impending labor. These may include strong, rhythmic uterine contractions or the loss of the mucus plug (“bloody show”). While the sudden onset of diarrhea at 37 weeks suggests preparation for birth, it should be considered alongside other physical signs, not as a standalone confirmation.
Other Common Causes in Late Pregnancy
Not every bout of late-term diarrhea signals impending labor; many other changes specific to the third trimester can affect the digestive system. Shifts in a person’s diet are a common culprit, as pregnant individuals may make last-minute changes to increase fiber, water, or other nutrients. Introducing a large quantity of new foods or supplements can naturally alter the consistency and frequency of bowel movements.
Prenatal supplements, particularly those containing high doses of certain minerals, can significantly impact gut function. Iron supplements, often prescribed to prevent or treat anemia, can cause constipation or trigger diarrhea. Magnesium, sometimes taken to alleviate leg cramps or promote sleep, is a known osmotic laxative that draws water into the intestines, leading directly to loose stools.
The physical presence of the full-term baby can also create digestive disruption, especially if the baby has moved lower into the pelvis (“lightening” or engagement). This descent places increased mechanical pressure on surrounding organs, disrupting normal gut motility. Additionally, increasing anxiety about the impending birth can contribute to symptoms, as emotional stress links directly to digestive function via the gut-brain axis.
Managing Symptoms and Recognizing Red Flags
The primary management strategy when experiencing diarrhea during late pregnancy is rigorous hydration to prevent dehydration. It is crucial to replace lost fluids and electrolytes, ideally by drinking water, clear broths, or oral rehydration solutions containing sodium and potassium. Maintaining adequate fluid volume is particularly important, as severe dehydration can potentially trigger uterine irritability.
Dietary adjustments can help firm up stools and soothe the digestive tract. Following a simple, bland diet, often referred to as the BRAT diet (Bananas, Rice, Applesauce, Toast), can be effective. These foods are low in fiber and easy to digest, reducing the workload on the intestines. Temporarily avoid high-fat, high-sugar, or heavily spiced foods, as well as dairy products, which can exacerbate symptoms.
While most cases of late-term diarrhea are harmless and resolve quickly, specific “red flags” require immediate medical consultation. Seek prompt attention if the diarrhea lasts longer than two days or is accompanied by signs of severe dehydration, such as dark-colored urine, excessive thirst, or dizziness upon standing. Other concerning symptoms include a fever above 100.4 degrees Fahrenheit, blood in the stool, or severe abdominal pain distinct from typical labor contractions. If the diarrhea is accompanied by intense, rhythmic contractions increasing in frequency and strength, this suggests the digestive symptom is an early sign of true labor.
Prenatal supplements, particularly those containing high doses of certain minerals, can significantly impact gut function. Iron supplements, which are often prescribed to prevent or treat anemia, can cause constipation in many people, but they can also trigger diarrhea in others. Similarly, magnesium, which is sometimes taken to alleviate leg cramps or promote sleep, is a known osmotic laxative that draws water into the intestines, leading directly to loose stools.
The physical presence of the full-term baby can also create digestive disruption, especially if the baby has moved lower into the pelvis, a process known as “lightening” or engagement. This descent places increased mechanical pressure on the surrounding organs, including the intestines, which can disrupt normal gut motility. Additionally, the increasing anxiety about the impending birth can contribute to symptoms, as the gut-brain axis links emotional stress directly to digestive function, sometimes causing an upset stomach or diarrhea.
The most important management strategy when experiencing diarrhea during late pregnancy is rigorous hydration to prevent dehydration. It is crucial to replace lost fluids and electrolytes, ideally by drinking water, clear broths, or oral rehydration solutions that contain a balance of sodium and potassium. Maintaining adequate fluid volume is particularly important at this stage of pregnancy, as severe dehydration can potentially trigger uterine irritability.
Dietary adjustments can help firm up stools and soothe the digestive tract. Following a simple, bland diet, often referred to as the BRAT diet (Bananas, Rice, Applesauce, Toast), can be effective. These foods are low in fiber and easy to digest, which helps reduce the workload on the intestines. It is best to temporarily avoid high-fat, high-sugar, or heavily spiced foods, as well as dairy products, which can exacerbate symptoms.
While most cases of late-term diarrhea are harmless and resolve quickly, there are specific “red flags” that require immediate medical consultation. Seek prompt attention if the diarrhea lasts longer than two days or is accompanied by signs of severe dehydration, such as dark-colored urine, excessive thirst, or dizziness upon standing. Other concerning symptoms include a fever above 100.4 degrees Fahrenheit, the presence of blood in the stool, or severe abdominal pain that is distinct from typical labor contractions. If the diarrhea is accompanied by intense, rhythmic contractions that are increasing in frequency and strength, this suggests that the digestive symptom is indeed an early sign of true labor.