Description
- Commonest serious neurological condition complicating pregnancy
- Central tension: seizure control vs teratogenicity/neurodevelopmental risk of AEDs
- Uncontrolled maternal seizures also carry fetal risk (hypoxia, trauma, SUDEP) - stopping AEDs is not the safe default
Epidemiology
- ~0.5-1% of pregnancies
- Seizure frequency: unchanged in ~2/3, worse in ~15-30% (often from non-adherence due to fear of harm, or altered pharmacokinetics), improved in a minority
Aetiopathogenesis
- Pregnancy alters AED pharmacokinetics
- inc plasma volume, renal clearance, hepatic metabolism (esp. lamotrigine clearance can rise 2-3x by 3rd trimester)
- dec protein binding -> free drug levels less predictable, especially phenytoin/valproate
- Teratogenicity is dose-dependent and drug-specific, greatest in the first trimester (organogenesis)
- Polytherapy raises malformation risk above any single agent
Diagnosis
- Clinical, pre-existing diagnosis in most; new-onset seizure in pregnancy needs standard work-up plus exclusion of eclampsia (check BP/proteinuria first, always)
- Monitor AED levels each trimester (esp. lamotrigine, levetiracetam) - adjust dose to maintain pre-pregnancy therapeutic level, not a fixed dose
- Fetal anomaly scan + detailed cardiac views if on known teratogenic AED
Management
Preconception (the highest-yield intervention)
- Aim for seizure freedom on the lowest effective dose of the least teratogenic agent, monotherapy, before conception
- High-dose folate 5 mg/day from preconception through 1st trimester (reduces neural tube defect risk, though evidence in AED-treated women is less robust than in the general population)
Drug choice - avoid where possible
- Sodium valproate - highest malformation risk (~10%, dose-dependent) + neurodevelopmental harm (lower IQ, autism spectrum risk) - avoid in pregnancy and in anyone who could become pregnant unless no alternative
- Topiramate - cleft lip/palate, low birth weight - avoid where possible
- Carbamazepine, phenobarbital, phenytoin - also carry inc malformation risk - avoid if alternatives suffice
Preferred agents
- Lamotrigine, levetiracetam - lowest malformation risk among AEDs studied, preferred first-line
- Oxcarbazepine - reasonable alternative
Antenatal
- Do not stop or abruptly change AEDs without specialist input - status epilepticus risk
- Multidisciplinary care - neurology/obstetric medicine + obstetrics
- Vitamin K - historic recommendation for enzyme-inducing AEDs (carbamazepine, phenytoin, phenobarbital) to reduce neonatal haemorrhagic disease risk; universal neonatal vitamin K now standard regardless
Intrapartum/postpartum
- Continue AEDs through labour (oral or IV substitution if nil by mouth)
- Sleep deprivation and stress raise seizure risk postpartum - safety planning for infant care (change table, bathing) if seizures poorly controlled
- Most AEDs compatible with breastfeeding (levels in breast milk low, except lamotrigine which reaches higher relative levels - still generally continued with infant monitoring)
Associations
- Major congenital malformations (NTD, cardiac, cleft, hypospadias) - drug- and dose-dependent
- Neurodevelopmental impairment - most strongly linked to valproate
- Small for gestational age (some AEDs)
- SUDEP and seizure-related trauma if control lost
Natural history & complications
- Most women with well-controlled epilepsy have uncomplicated pregnancies
- Postpartum - falling AED levels as pharmacokinetics normalise, especially lamotrigine - dose often needs reducing over following weeks to avoid toxicity
- Preconception counselling before every pregnancy of reproductive age is the standard of care
7 of 7 sections written · drafted 2026-09-13