What is the first‑line management of constipation in a pregnant woman in her first trimester?

First-Line Management of Constipation in First Trimester

Start with dietary fiber increase to approximately 30 g/day through fruits, vegetables, whole grains, and legumes, combined with adequate fluid intake; if this fails after 1 week, initiate polyethylene glycol (PEG) 17g daily as the preferred first-line pharmacological therapy. 1, 2, 3

Initial Non-Pharmacological Approach

Dietary modifications should be attempted first:

• Increase fiber intake to 30 g/day through specific food sources including prunes, raisins, apples, pears, berries, leafy greens (broccoli, kale, spinach), sweet potatoes, 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) 1, 3
• Ensure adequate water intake to soften stools and improve transit time 1, 2, 3
• Allow sufficient time for bowel movements and use relaxation techniques to avoid straining 3

Pharmacological Treatment Algorithm

If dietary changes fail after 1 week, escalate systematically:

Step 1: Osmotic Laxatives (Preferred First-Line)

• Polyethylene glycol (PEG) 17g daily is the preferred first-line pharmacological therapy due to safety profile and minimal systemic absorption 2, 3, 4
• Lactulose is an alternative but causes more bloating than PEG, making it second choice 2, 3, 4
• Magnesium hydroxide 400-500 mg daily is safe and effective but use cautiously in renal impairment 2, 3

Step 2: Bulk-Forming Agents

• Psyllium husk or methylcellulose are safe due to minimal systemic absorption and can be used if osmotic laxatives are not tolerated 1
• Note that excessive fiber can cause maternal bloating 1

Step 3: Stimulant Laxatives (Use Cautiously)

• Stimulant laxatives should generally be avoided or used only short-term as safety data are conflicting 1, 2
• If needed, senna has some evidence supporting use in pregnancy 5
• Avoid prolonged use to prevent dehydration or electrolyte imbalances 6

Important Clinical Considerations

Specific to first trimester:

• Approximately 20-40% of pregnant women experience constipation due to increased progesterone slowing GI motility 1
• Screen for hemorrhoids which occur in approximately 80% of pregnant women; hydrocortisone foam is safe in third trimester if needed 1, 2, 3
• Assess for iron supplementation effects as this commonly contributes to constipation in pregnancy 3

Critical Pitfalls to Avoid

• Do not use bulk laxatives for opioid-induced constipation if the patient is on pain medications 2, 3
• Avoid enemas in patients with recent colorectal/gynecological surgery, anal trauma, or recent pelvic radiotherapy 2, 3
• Use magnesium salts cautiously as they can lead to hypermagnesemia, particularly in renal impairment 2

Monitoring and Follow-Up

• Reassess bowel movement frequency and consistency after initiating treatment with goal of achieving soft, formed stools every 1-2 days 2, 3
• Adjust treatment based on response, escalating through the algorithm as needed 2, 3
• Evaluate for secondary causes including hypothyroidism and hypercalcemia if constipation is refractory 3

When to Hospitalize

• Severe dehydration or inability to tolerate oral intake requires hospitalization for IV fluid replacement 2, 3
• Implement anticoagulant thromboprophylaxis during hospital stay to prevent venous thromboembolism 2