The Pregnant Patient on Lithium
Ms. R, 29, has bipolar I disorder and has been stable on lithium 900 mg daily (level 0.8 mEq/L) for three years. She is now 8 weeks pregnant (unplanned) and presents urgently, worried about the medication. She has had two prior manic episodes with psychotic features, both requiring hospitalization, and one prior depressive episode with suicidal ideation. She has no current symptoms, is sleeping well, and denies SI. She asks, "Should I stop the lithium?" She is tearful and says she is terrified of harming the baby.
1. How do you counsel her about lithium in pregnancy?
Read the worked answer
Frame this as risk of relapse vs. risk of teratogenicity, individualized to her history.
- Teratogenicity: Lithium is associated with Ebstein anomaly, but the absolute risk is low (~1 in 1,000 vs. background ~1 in 20,000); the classic "high risk" figure came from older registry data. Risk is highest with first-trimester exposure.
- Relapse risk: Abrupt discontinuation in a woman with prior psychotic mania and prior suicidal depression is dangerous - relapse risk is high (roughly half or more within months), and relapse itself harms mother and fetus (hospitalization, suicide risk, poor prenatal care).
- Do not stop abruptly. If she wishes to avoid lithium, taper slowly with close monitoring and a plan; if she continues, use the lowest effective dose and monitor levels closely.
- Pregnancy physiology: Renal clearance rises, so levels fall; check levels frequently (every 2–4 weeks, more often later) and after delivery when clearance drops rapidly - risk of toxicity.
- Co-manage with OB/maternal-fetal medicine; ensure anatomy scan and fetal echocardiogram (~18–20 weeks); continue monitoring for hypothyroidism and diabetes insipidus.
2. She decides she wants to stop lithium. What is your plan?
Read the worked answer
Respect her autonomy while protecting safety.
- Informed consent documented: Discuss relapse risk, teratogenicity, and alternatives.
- Taper, don't stop: Gradual reduction over weeks with frequent visits (every 1–2 weeks initially) and mood monitoring.
- Alternative prophylaxis: Discuss options - lamotrigine (relatively favorable in pregnancy; needs slow titration and monitoring for rash), or a second-generation antipsychotic (e.g., quetiapine) with attention to metabolic effects. Avoid valproate and carbamazepine.
- Psychotherapy and sleep hygiene: Emphasize sleep protection and early warning signs.
- Safety plan: Identify early warning signs of mania/depression, involve partner/family, and set clear thresholds for urgent contact.
- Postpartum planning: Highest risk period is postpartum; plan for close monitoring, lactation consultation (lithium is generally compatible with breastfeeding with monitoring, but individualize), and relapse prevention.
- Coordinate with OB and MFM; document shared decision-making.
3. At 32 weeks she calls reporting vomiting, tremor, and confusion. What do you do?
Read the worked answer
This is a medical emergency - suspect lithium toxicity (or preeclampsia with neuro symptoms).
- Direct her to emergency care immediately (do not manage by phone).
- Why: Vomiting, tremor, and confusion are classic for lithium toxicity; pregnancy-related changes in renal clearance, dehydration from vomiting, and drug interactions (NSAIDs, thiazides) raise levels. Toxicity can cause seizures, arrhythmia, and renal failure.
- At the ED: Check lithium level, electrolytes, renal function, and BP/urine protein (preeclampsia can mimic). Hold lithium until levels return.
- After stabilization: Reassess dosing, hydration, and interacting medications; consider whether lithium remains appropriate at this stage or whether to transition.
- Document the call, advice given, and follow-up.