Farting During Pregnancy: Why Gas Increases and What Is Normal
Increased flatulence is one of the earliest and most persistent digestive changes of pregnancy, driven largely by the hormone progesterone. Here is the science behind why expectant mothers pass more gas and what they can do about it.
Why Pregnancy Increases Flatulence
From the earliest weeks of pregnancy, the body ramps up production of progesterone, a hormone that relaxes smooth muscle throughout the body to help the uterus accommodate a growing baby. Unfortunately, the same muscle-relaxing effect slows the entire gastrointestinal tract. Food lingers longer in the stomach and intestines, giving gut bacteria more time to ferment undigested carbohydrates and release hydrogen, methane and carbon dioxide. The result is more gas, more bloating and more frequent flatulence. This slowdown, sometimes described as reduced gut motility, begins in the first trimester and often continues until delivery. Because progesterone rises steadily, many women notice that gas is one of the very first signs that something has changed, sometimes even before a pregnancy test is positive.
Hormonal and Physical Changes
As pregnancy progresses, hormones are joined by simple mechanics. The expanding uterus presses on the intestines and stomach, crowding the digestive organs and making it harder for gas to move smoothly through the bowel. In the third trimester, this pressure peaks, which is why many women feel most bloated in the final months. The hormone relaxin, which loosens ligaments and joints in preparation for birth, may further relax the digestive tract. Slower transit also encourages constipation, and a backed-up colon traps gas that would otherwise pass. Together these changes explain why flatulence often waxes and wanes across the three trimesters, easing slightly in the second trimester for some women before returning as the baby grows larger. Reduced physical activity and long periods of sitting or lying down later in pregnancy can slow intestinal transit even further, giving gas more time to accumulate.
Common Triggers and Timing
Several pregnancy-specific factors amplify gas beyond the hormonal baseline. Prenatal vitamins, especially those high in iron, are notorious for causing constipation and bloating. Dietary shifts, cravings and eating larger volumes of gas-producing foods such as beans, broccoli, onions and dairy add fermentable material to a slower gut. Swallowing air while eating quickly, drinking carbonated beverages or chewing gum, a habit known as aerophagia, contributes belching and lower-tract gas. Dehydration worsens constipation, compounding the problem. Many women find flatulence is worst in the early morning or after large meals. While the odor and frequency can be embarrassing, the pattern is a normal physiological response and not a sign that anything is wrong with the pregnancy. Stress and disrupted sleep, both common during pregnancy, can also alter gut function and heighten the perception of bloating and discomfort.
Managing Gas During Pregnancy
Most pregnancy gas can be eased with gentle lifestyle measures. Eating smaller, more frequent meals reduces the fermentation load, while slowing down and chewing thoroughly limits swallowed air. Staying well hydrated and getting regular light exercise, such as walking or prenatal yoga, keeps the bowel moving and combats constipation. Fibre helps, but should be increased gradually to avoid a sudden gas spike. Identifying personal trigger foods through a simple diary can reveal culprits without cutting nutrition. Any medication or supplement, including simethicone or a change in prenatal vitamin, should be discussed with a doctor or midwife first. Persistent severe pain, blood in the stool or gas accompanied by fever warrants medical attention, as these may signal a problem beyond ordinary pregnancy digestion.
Did You Know?
- Progesterone levels can rise more than tenfold during pregnancy, which is the main reason digestion slows and gas increases.
- Increased flatulence and bloating are sometimes among the very first symptoms women notice, occasionally before a missed period.
- The growing uterus can displace the intestines upward and to the sides, physically squeezing gas-filled loops of bowel.
- Iron in prenatal vitamins is a leading cause of pregnancy constipation, which in turn traps more intestinal gas.
Fun Fact
Some women report that their sense of smell becomes dramatically sharper in early pregnancy, meaning they may notice their own gas more acutely, even though the odor itself has not actually changed.
Sources
- Bradley, C. S. et al., Constipation in Pregnancy: Prevalence, Symptoms, and Risk Factors, Obstetrics & Gynecology, 2007
- Body, C. & Christie, J. A., Gastrointestinal Diseases in Pregnancy, Gastroenterology Clinics of North America, 2016
- American College of Obstetricians and Gynecologists, Problems of the Digestive System During Pregnancy, 2021