Constipation in the Third Trimester

By trimester

Weeks 1–13

1st trimester

Constipation often starts early, since rising progesterone slows digestion right away and prenatal iron adds to the effect. This page focuses on late pregnancy: see our general constipation guide for first-trimester specifics.

Weeks 14–27

2nd trimester

The same fiber, fluid, and movement habits from early pregnancy still apply. If they're not quite enough, a stool softener like docusate is often the next step your provider suggests.

Weeks 28–birth

3rd trimester

This is when constipation is often at its worst. Your growing uterus presses on your intestines and rectum right as you're likely moving around less, and iron needs peak too. Work up the ladder in order: fiber and water first, then a fiber supplement, then a stool softener like docusate, then an osmotic laxative such as polyethylene glycol or magnesium hydroxide if your provider okays it. Skip castor oil and other stimulant laxatives unless your provider specifically tells you to use one, since they can cramp your uterus along with your bowel this close to delivery.

What does the evidence show for constipation in the third trimester?

• Constipation on its own hasn't been shown to raise the risk of birth defects, and it's not expected to get in the way of breastfeeding once your baby arrives. 1
• Skip castor oil for constipation relief this late in pregnancy: it's sometimes used to try to jump-start labor because it can cramp the bowel and uterus at the same time. 2
• Docusate (Colace) is a stool-softening step that's considered fine to use as directed, since very little of it actually enters your bloodstream. 3
• Prenatal iron is a common trigger for third-trimester constipation, and pregnant women need more of it than usual (27 mg a day) since blood volume keeps climbing late in pregnancy. 4
• The usual game plan is fiber, fluids, and movement first, then a bulk-forming or stool-softening product if needed, saving stronger osmotic or stimulant laxatives for short, occasional use rather than every day. 5
• Rectal bleeding or blood in the stool, constant abdominal pain, an inability to pass gas, vomiting, fever, lower back pain, or losing weight without trying are signs constipation needs prompt medical evaluation rather than more home fiber and fluids. 6

When should I call my provider about constipation in the third trimester?

Call your provider the same day for rectal bleeding or blood in your stool, constant or severe abdominal pain, an inability to pass gas, vomiting, or a fever alongside the constipation. Lower back pain or losing weight without trying are two more combinations worth a same-day call rather than more home fiber and fluids. These point to something beyond ordinary pregnancy constipation and need a clinician to sort out. When in doubt, call your obstetric team the same day. Early input almost always beats waiting, and the on-call line exists exactly for this.