Epilepsy drug dose key to fetal risk

An 11-year study has revealed the safest effective treatment for women with epilepsy considering pregnancy.

The four most common drugs are all linked with a higher risk of birth defects, but work published in The Lancet Neurology explains how a 3900 patient study could assist doctors in prescribing to pregnant women with epilepsy.

Between 0·3% and 0·7% of all pregnancies are in women with epilepsy. Most will use anti-epileptic drugs as uncontrolled seizures carry a risk to both mother and fetus. However, epilepsy treatments such as valproic acid can increased risks of birth defects.

The latest research, from the Karolinska Institute in Sweden and the University of Pavia in Italy, also looked in detail at other drugs such as carbamazepine, lamotrigine and phenobarbital. Researchers studied 3909 women and 4540 pregnancies. It found that there were 230 pregnancies involving major birth defects, including heart defects and neural tube defects such as spina bifida.

An increase in the rate of birth defects was noted with increasing dose for all drugs. The rate was lowest for low doses of the drugs lamotrigine (less than 300mg per day) and carbamazepine (less than 400mg per day).

None of the drugs proved to be risk-free, however, the lowest risk was linked to smaller doses of lamotrigine and carbamazepine. The researchers also stressed that the vast majority of women still gave birth to perfectly healthy babies and that 'dose selection is as crucial as the choice of drug.'