Pharmacology and Prescribing in Midwifery
Pharmacology questions test whether you can choose a medicine that is safe in pregnancy or lactation, write a legal prescription, and recognise common teratogens and interactions. The exam expects practical prescribing decisions and awareness of your scope of practice.
Core rules and concepts
- Prescribe only within your competence and formulary. Check the BNF and current pregnancy or lactation advice; document indication, dose, route, frequency and duration.
- Pregnancy changes pharmacokinetics: increased plasma volume and renal clearance can lower drug levels; hepatic metabolism changes; avoid live vaccines.
- Common midwifery medicines include folic acid 400 micrograms (5 mg for high risk), iron for anaemia, anti-D immunoglobulin, oxytocin, magnesium sulfate, antibiotics and analgesia.
- Paracetamol is first-line analgesia in pregnancy. Avoid NSAIDs after 30 weeks because of ductus arteriosus constriction and oligohydramnios. Avoid codeine in breastfeeding because of neonatal sedation.
- Teratogens: sodium valproate (neural tube defects and neurodevelopmental harm), warfarin, isotretinoin, tetracyclines, ACE inhibitors and fluoroquinolones.
- Infection: avoid nitrofurantoin at term; trimethoprim is not first-line in the first trimester; penicillins and erythromycin are generally safe.
- Lactation: most antibiotics, paracetamol, ibuprofen and insulin are compatible. Check for infant sedation and effects on milk supply.
- Legal prescription: patient identifiers, date, signature, prescriber details, allergy status and consent.
Worked example
A breastfeeding woman has a severe headache and asks for codeine. Reasoning: codeine is contraindicated in breastfeeding because CYP2D6 ultrarapid metabolisers convert it to morphine, causing infant sedation and respiratory depression. Offer paracetamol or ibuprofen instead, and assess the headache for pre-eclampsia or other pathology.
Traps
- Prescribing an unlicensed medicine without documenting the rationale.
- Using NSAIDs in the third trimester.
- Assuming all antibiotics are safe in pregnancy.
- Continuing sodium valproate without specialist review.
- Writing a prescription without allergy status.
Key points
- Check BNF and pregnancy or lactation safety before prescribing.
- Avoid NSAIDs after 30 weeks and codeine during breastfeeding.
- Sodium valproate is a major teratogen; avoid in pregnancy.
- Paracetamol is first-line analgesia in pregnancy.
- Document indication, dose, allergy status and consent.