Constipation in Pregnancy Management: PLAB 1 / UKMLA Question
Clinical Exam-Style Scenario
A 28-year-old woman attends the antenatal clinic at 24 weeks' gestation. She complains of worsening constipation over the last 3 weeks, passing hard stools only once every 3-4 days with straining.
She has already increased her dietary fibre intake significantly and is drinking 2-3 litres of water daily, as per previous midwife advice, but her symptoms have not improved. She takes pregnancy multivitamins but no other medications.
Which is the most appropriate next step in the management of her constipation?
A. Prescribe oral Bisacodyl
B. Prescribe oral Docusate Sodium
C. Prescribe oral Ispaghula husk
D. Prescribe oral Lactulose
E. Prescribe oral Senna
Answer & Explanation
Correct Answer: C. Prescribe oral Ispaghula husk
This question tests your knowledge of the NICE Stepped-Care Pathway for treating constipation in pregnancy. You must follow the steps in order; skipping a step will lose you the mark.
1. The Step-Wise Management Protocol
Step 1 (Lifestyle): Increase dietary fibre, fluid intake, and gentle exercise.
Status: Failed. The patient has already tried this ("increased fibre... drinking 2-3 litres").
Step 2 (First-Line Drug): Bulk-forming laxatives (e.g., Ispaghula husk/Fybogel).
Why: They mimic dietary fibre, are not systemically absorbed, and are considered the safest option for the fetus.
Step 3 (Second-Line): Osmotic laxatives (e.g., Lactulose or Macrogols).
When to use: If stools remain hard despite bulk-forming agents.
Step 4 (Third-Line): Stimulant laxatives (e.g., Senna or Bisacodyl).
When to use: Short-term use only if stools are soft but difficult to pass, or if other methods fail.
2. Analysis of Distractor Options
A. Bisacodyl & E. Senna (Stimulants): These are Third-Line. They stimulate the bowel nerves. While generally safe in standard doses, there is a theoretical caution about stimulating uterine contractions, so they are reserved for when safer options fail.
B. Docusate Sodium (Stool Softener): Often used in combination but is not the specific first-line recommendation over bulk-forming agents.
D. Lactulose (Osmotic): This is the Second-Line option. You would only prescribe this if the Ispaghula husk failed to work or caused excessive bloating.
3. PLAB-UKMLA Exam Tip
Always look for the phrase "already tried dietary measures" in the vignette.
If NOT tried —> Answer is Diet/Fluids.
If TRIED —> Answer is Ispaghula Husk.
If Ispaghula FAILED —> Answer is Lactulose.
References & Guidelines
NICE CKS: Constipation in pregnancy
UKTIS (UK Teratology Information Service): Safety of laxatives in pregnancy.
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