Constipation in the first trimester is extremely common, and several options are considered safe to use this early in pregnancy. The safest starting point is increasing fiber and water intake, followed by over-the-counter stool softeners or osmotic laxatives if lifestyle changes aren’t enough. Here’s what works, what’s safe, and how to get relief quickly.
Why the First Trimester Causes Constipation
Rising progesterone levels are the main culprit. Progesterone acts directly on the smooth muscle cells lining your gut, triggering the release of nitric oxide, which relaxes those muscles. This slows the wave-like contractions that normally push food through your intestines. The result: everything moves more slowly, your colon absorbs more water from the stool, and what’s left becomes hard and difficult to pass.
This isn’t a minor hormonal nudge. Progesterone essentially rewires the signaling pathways that tell your intestinal muscles to contract, blocking them at multiple points simultaneously. That’s why constipation can hit hard and early, sometimes before you even realize you’re pregnant. Prenatal vitamins containing iron (especially ferrous sulfate, the most common form) can make it worse.
Start With Fiber, Water, and Movement
The first-line approach is straightforward: aim for 20 to 35 grams of fiber per day, drink plenty of water, and get some moderate daily exercise like walking. This combination works for many women without needing anything else. For reference, most Americans eat about 15 grams of fiber daily, so you likely need to roughly double your current intake.
Good sources include beans, lentils, whole grains, berries, pears, broccoli, and avocado. Add fiber gradually over a week or two rather than all at once, since a sudden spike can cause bloating and gas, which are already common in the first trimester. Every increase in fiber should come with extra water, at least 8 to 10 glasses a day.
Prunes and Prune Juice
Prunes are one of the most effective natural remedies, and they work through multiple mechanisms at once. They contain sorbitol, a sugar alcohol that draws water into the intestines, along with pectin (a type of soluble fiber) and polyphenols that all contribute to softer, easier-to-pass stool. A randomized trial found that about 54 grams of prune juice daily (roughly a quarter cup) improved both stool consistency and the subjective feeling of constipation over eight weeks. Five to six whole prunes a day is a common starting dose. They’re safe in pregnancy and worth trying before moving to anything from the pharmacy aisle.
Stool Softeners: Docusate Sodium
If dietary changes aren’t doing enough, stool softeners like docusate sodium (sold as Colace) are generally considered safe during pregnancy, including the first trimester. Docusate works by moistening the stool so it passes more easily. The active ingredient is only minimally absorbed by your body, which means very little reaches the developing baby. Docusate calcium (Surfak) works the same way and carries the same safety profile. Both are available without a prescription.
Stool softeners won’t produce a dramatic effect. They’re best for mild to moderate constipation or as a preventive measure when you know your prenatal vitamin tends to back you up. If you’re already significantly constipated, you may need something stronger.
Osmotic Laxatives: Polyethylene Glycol
Polyethylene glycol 3350 (the active ingredient in MiraLAX) is widely used during pregnancy and is considered the drug of choice for chronic constipation in pregnant women by the American Academy of Family Physicians. It works by drawing water into the colon to soften stool. Like docusate, it’s minimally absorbed in the gastrointestinal tract, so very little enters your bloodstream.
It’s classified as pregnancy category C, which means there aren’t large controlled studies in pregnant women, but the minimal absorption makes it unlikely to cause harm. It typically takes one to three days to work, so it’s not an instant fix. You mix the powder into a glass of water once daily. If you’ve tried fiber and stool softeners without success, this is a reasonable next step.
Bulk-Forming Laxatives: Psyllium Husk
Psyllium husk (found in Metamucil and similar products) is a concentrated fiber supplement that absorbs water in the gut and adds bulk to stool, which stimulates the intestines to move things along. The typical dose is one to two rounded teaspoons mixed into a full 8-ounce glass of water, taken one to three times daily. The critical detail with psyllium is that you must drink enough water with it. Without adequate fluid, bulk-forming laxatives can actually cause blockages in the digestive tract. If you’re already struggling to stay hydrated due to first-trimester nausea, psyllium may not be the best choice until you can reliably keep fluids down.
Check Your Prenatal Vitamin
Your prenatal vitamin could be a significant contributor to the problem. Ferrous sulfate, the most commonly recommended form of iron in prenatal supplements, is notorious for causing constipation and digestive upset. If iron is making things worse, look for a prenatal that uses iron bisglycinate instead. This form is well absorbed and much less likely to cause constipation. Some brands, like Pure Encapsulations, use this form and provide 100 percent of the iron needed during pregnancy. Switching the form of iron rather than skipping it entirely lets you keep your iron levels up without paying for it with your digestion.
What to Avoid in the First Trimester
Stimulant laxatives (like senna or bisacodyl) are not a good first choice during pregnancy, particularly in the first trimester. These work by forcing the intestinal muscles to contract, and there are concerns about triggering uterine contractions or causing electrolyte imbalances with regular use. Castor oil should be avoided entirely, as it can stimulate uterine contractions. Mineral oil is also not recommended during pregnancy because it can interfere with the absorption of fat-soluble vitamins that are critical during fetal development.
When Constipation Needs Medical Attention
Most first-trimester constipation responds to the approaches above, but certain symptoms warrant a call to your provider: blood in the stool, severe abdominal pain or cramping, persistent constipation that doesn’t improve with lifestyle changes and over-the-counter options, unexplained weight loss, or vomiting. These could signal something beyond routine pregnancy constipation that needs evaluation.