Why are hemorrhoids more common during pregnancy and postpartum?

Hemorrhoids are particularly common during the last trimester of pregnancy and the first month postpartum.^[1] This increased risk arises for a number of reasons. During pregnancy, the combination of increased blood volume (more circulating blood) and a rise in abdominal pressure from the growing fetus can cause blood to pool in the rectal/anal region.^[2] Additionally, progesterone, a hormone that is elevated during pregnancy, relaxes smooth muscles in the walls of veins and the gastrointestinal tract. Veins may become more relaxed, allowing vessels to dilate and blood to pool, while gut motility slows, which can contribute to constipation. Reduced physical activity and changes in diet may also contribute to constipation during pregnancy.^[3][2]

During labor, vaginal delivery creates an immense amount of pressure in the abdomen and rectal area, which can lead to, or worsen, hemorrhoids. Factors that may increase the risk of hemorrhoids during pregnancy and postpartum include a history of constipation or anal problems, straining for more than 20 minutes during delivery, and a newborn birth weight of more than 3,800 grams (8 lbs, 6 oz).^[1] Consuming a high-fiber diet with adequate fluids and staying active may help to prevent hemorrhoids in pregnancy and postpartum. A randomized controlled trial found that dietary and behavioral modifications reduced the risk of hemorrhoids by 60%. The dietary component included daily consumption of at least 1.5 liters of fluids, bran (1 tablespoon), 2 to 5 prunes, a serving of nuts, and several servings of fruits and vegetables. Additionally, participants were encouraged to exercise and walk 30–60 minutes per day, 3–5 times per week, and follow good bowel habits (not ignoring the urge to defecate and spending less than 3 minutes on the toilet).^[3]