What is the recommended medical management for constipation in a pregnant patient?

Medical Management of Constipation in Pregnancy

Start with dietary fiber (30 g/day) and adequate hydration, then escalate to polyethylene glycol (PEG) 17g daily as first-line pharmacological therapy if dietary measures fail after one week. 1, 2, 3

Stepwise Treatment Algorithm

Step 1: Non-Pharmacological Interventions (First-Line)

• Increase dietary fiber to approximately 30 g/day through fruits, vegetables, whole grains, and legumes 1, 2, 3
• Aim for 3-4 servings of fruits and 3-4 servings of vegetables daily (1 medium fruit, 1/2 cup cut-up fruit, 1 cup raw leafy vegetables, or 1/2 cup cooked vegetables per serving) 4, 2
• Prioritize high-fiber foods: prunes, raisins, apples, pears, berries, broccoli, kale, spinach, sweet potatoes, and legumes 4
• Ensure adequate fluid intake, particularly water, to soften stools and improve transit time 4, 2, 3
• Allow sufficient time for bowel movements and use relaxation techniques to avoid straining 2, 3

Step 2: Bulk-Forming Agents (If Dietary Changes Insufficient)

• Psyllium husk or methylcellulose are safe during pregnancy due to minimal systemic absorption 4, 5
• These agents improve stool viscosity and transit time while increasing bulk 4
• Caution: Excessive fiber can cause maternal bloating; avoid bulk laxatives if patient is on opioid pain medications 4, 2

Step 3: Osmotic Laxatives (Preferred Pharmacological Therapy)

• Polyethylene glycol (PEG) 17g daily is the preferred first-line pharmacological therapy if dietary changes and bulk-forming agents fail after 1 week 1, 2, 3
• PEG has been shown to work faster than lactulose, with significant improvement by the second week of treatment 6
• Lactulose is also safe but causes more bloating than PEG, making it a second-choice osmotic laxative 1, 4, 2, 3
• Magnesium hydroxide 400-500 mg daily is safe and effective but use cautiously in patients with renal impairment to avoid hypermagnesemia 2, 3

Step 4: Additional Options for Severe Cases

• Glycerin suppository may be considered for immediate relief if the patient is severely uncomfortable 2
• Stimulant laxatives (such as senna) should generally be reserved for short-term use only when other measures fail, as safety data are conflicting 4, 5, 7
• Avoid prolonged use of osmotic or stimulant laxatives to prevent dehydration or electrolyte imbalances 7

Special Considerations

Associated Hemorrhoids

• Approximately 80% of pregnant women develop hemorrhoids as a complication of constipation 4, 3
• Hydrocortisone foam is safe in the third trimester for symptomatic relief of hemorrhoids 4, 2, 3

Severe Cases Requiring Hospitalization

• Hospitalize for IV fluid replacement if severe dehydration or inability to tolerate oral intake occurs 2, 3
• Implement anticoagulant thromboprophylaxis during hospital stay to prevent venous thromboembolism 2, 3

Critical Pitfalls to Avoid

• Do not use bulk laxatives for opioid-induced constipation in patients on pain medications 2, 3
• Avoid enemas in patients with recent colorectal/gynecological surgery, recent anal trauma, or recent pelvic radiotherapy 2, 3
• Magnesium and sulfate salts can lead to hypermagnesemia; use cautiously in renal impairment 2
• Do not withhold necessary treatments solely because the patient is pregnant; individualize after risk-benefit assessment 1

Monitoring and Follow-Up

• Reassess bowel movement frequency and consistency after initiating treatment, with a goal of achieving soft, formed stools every 1-2 days 2, 3
• If dietary changes are ineffective after 1 week, escalate to PEG 2, 3
• If constipation is refractory to standard treatment, evaluate for secondary causes including hypothyroidism, hypercalcemia, and iron supplementation effects 3
• Adjust treatment based on response, escalating through the algorithm as needed 2, 3

Understanding the Evidence

The 2024 American Gastroenterological Association guidelines provide the most authoritative framework, clearly stating that treatment options include dietary fiber, lactulose, and PEG-based laxatives 1. The more detailed 2025 guidance consistently prioritizes PEG over lactulose due to less bloating 2, 3, which is supported by a 2020 randomized controlled trial showing PEG works faster than lactulose 6. Most laxatives have minimal systemic absorption and are not expected to increase congenital anomaly risk 7, though long-term use of osmotic and stimulant laxatives should be avoided to prevent maternal complications 7.