Prescribing in Pregnancy

👩‍🍼 Always consider all women of childbearing age pregnant until proven otherwise before prescribing. Even common medications can cross the placenta and harm the fetus. Always check the 💊 BNF and weigh risk vs benefit carefully.

📖 About

• Most drugs cross the placenta; some have no effect, while others are teratogenic or toxic.
• 👶 First trimester (weeks 1–12): Highest risk for congenital malformations (organogenesis).
• 🤰 Second & third trimesters: Drugs may cause growth restriction, functional defects, or direct fetal toxicity.
• There is no drug that is 100% "safe" in pregnancy.
• ⚠️ General principle: Use the lowest effective dose for the shortest duration.
• 🚫 Avoid all unnecessary medications, especially in the first trimester.

✅ Drugs considered relatively safe

• 💉 Penicillins & Cephalosporins (safe antibiotics)
• 💉 Heparin (anticoagulation – does not cross placenta; Warfarin is unsafe)
• 💊 Ranitidine (historically used; though now largely replaced by famotidine/PPIs if needed)
• 💊 Paracetamol (analgesia of choice)
• 💊 Codeine (short-term, with caution)

🚫 Drugs to avoid (BNF check essential)

• ❌ Antibiotics: Tetracyclines, Streptomycin, Quinolones
• ❌ Cardiovascular: Warfarin, Thiazides, ACEi/ARBs
• ❌ Neurological/Psychiatric: Lithium, Valproate, Phenytoin, Barbiturates
• ❌ Others: NSAIDs (esp. 3rd trimester), Retinoids, Cytotoxic drugs, Thalidomide
• ❌ Lifestyle: Alcohol, recreational drugs

⚠️ Unsafe Drugs and Potential Effects

💡 Teaching Pearls

• 📌 Always balance maternal benefit vs fetal risk – e.g., uncontrolled maternal epilepsy or hypertension may be more harmful than the medication itself.
• 📌 Pre-pregnancy counselling is key in women of childbearing age with chronic disease (neurology, rheumatology, psychiatry, cardiology).
• 📌 Use folic acid supplementation in women taking anticonvulsants to reduce neural tube defects.
• 📌 Record drug exposure in the notes & inform antenatal services for fetal monitoring.