Some epidemiological studies have suggested an increased risk of death during pregnancy among women with epilepsy compared to women without epilepsy. A recent study by Edey and colleagues examined the cause of death among pregnant women with epilepsy. The researchers examined data obtained from the United Kingdom Enquiry into Maternal and Child Health, a national registry that includes all maternal deaths during or immediately after pregnancy, between 2006-2008. Among all 261 deaths, 14, or 5%, occurred in women with epilepsy. Of these deaths in women with epilepsy, nine were during the pregnancy and five were soon after delivery. The majority of these deaths (79%) were due to sudden unexpected death in epilepsy (SUDEP). The remaining three deaths were due to trauma, drowning and anoxic brain injury. Based on the number of pregnancies reported between 2006-2008 and estimates that 0.6% of all pregnant women have epilepsy, the authors estimate that epilepsy-related death occurred in 1 of 1,000 pregnancies in women with epilepsy. This rate is about 10 times higher than the overall maternal mortality rate during this time period.
Nine of the women with epilepsy who died during the study period were taking lamotrigine. This is not necessarily surprising as lamotrigine is commonly given to women of childbearing age because its low risk of birth defects. The authors speculate there may be a relationship between lamotrigine use and SUDEP during pregnancy. Lamotrigine metabolism can increase by as much as 50% during pregnancy leading to lower-than-expected drug levels and a risk for breakthrough seizures. It is possible that this change in seizure control puts pregnant women at higher risk for seizure-related death such as SUDEP and accidents.
Because of the limited nature of the data, the accuracy of these mortality estimates is uncertain. The registry captured all pregnancies that were noted by obstetricians, typically those that lead to delivery, but it is likely that many pregnancies, such as those that ended in miscarriage, were not included. In addition, the overall number of women with epilepsy in this group was unknown. We will need additional studies to see if pregnancy, either through its effects on anti-epileptic drug levels or through other means, increases SUDEP risk in women with epilepsy. In the meantime, women taking medications whose metabolism is affected by pregnancy should be closely followed to ensure anti-epileptic drug levels do not fall too low, risking breakthrough seizures and their complications.