Published: February 2009

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Anticonvulsants and congenital malformations

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Prescriber Update 30(1): 1
February 2009

Prescribers are reminded of the risk of congenital malformations associated with the use of anticonvulants (anti-epileptics) during pregnancy, and the importance of counselling for all women of child-bearing age prescribed anticonvulsants.

Observational data from 3500 females included in the United Kingdom Epilepsy and Pregnancy Registry demonstrated the following:

• 4.2% congenital malformations for all antiepileptics versus 3.5% with untreated epilepsy.
• 6.0% congenital malformations with polytherapy versus 3.7% with monotherapy.
• 6.2% congenital malformations with valproate monotherapy.
• 2.2% congenital malformations with carbamazepine monotherapy¹.

A prospective observational study across 25 epilepsy centres (NEAD study) demonstrated that serious adverse outcomes for monotherapy ranged from 1% for lamotrigine to 20.3% for valproate².

Common craniofacial anomalies include epicanthal folds, broad nose with a flat bridge, anteverted nostrils, shallow philtrum and a thin upper and thick lower lip. Associated disorders may include developmental delay, neurologic abnormalities, congenital heart defects and finger abnormalities.

As uncontrolled epilepsy in pregnant woman is a serious and potentially life-threatening condition for both mother and child, treatment options must be carefully considered. Medsafe recommends that the most effective medicine should be used at its lowest effective dose.

It is important that all women of child-bearing age taking anticonvulsants receive counselling on the risk of congenital malformations associated with the use of anticonvulsants. However, the occurrence of an unexpected pregnancy should not trigger sudden discontinuation of therapy.

References

1. Breen D. and Davenport R. (2006). Teratogenicity of antiepileptic drugs: Women should consider stopping, minimizing, or switching drugs before pregnancy British Medical Journal 333:615-6.
2. Meador J. et al. (2006). In-utero antiepileptic drug exposure: Fetal death and malformations Neurology 67:407-12.