NASHVILLE, Tenn. ― Some antiseizure medications (ASMs) taken by pregnant women with epilepsy may lead to low birth weight for their infants, suggests a study of more than 4 million children being presented at the American Epilepsy Society Annual Meeting.
The study is the largest to assess how ASMs affect birth weight. Low birth weight (5-½ pounds or less) has been associated with an increased risk of short-term health issues in newborns, such as breathing problems and infections, as well as long-term health issues such as heart disease. Additionally, a number of ASMs are known to cause birth defects.
Most women with epilepsy need to continue taking ASMs during pregnancy because seizures can lead to injury or death for them or their fetus. The goal is to determine which ASMs do not cause birth defects and are not associated with low birth weight but are effective at stopping seizures. The new study suggests lamotrigine may be a good option to consider because it was not associated with lower birth weight or birth defects. Conversely, carbamazepine, which is often prescribed to pregnant women because it is not linked to birth defects, was associated with lower birth weight in the study.
“Most concern has centered around which antiseizure medications can cause birth defects and neurodevelopment issues in children, but clearly there have been gaps in our understanding of other risks of prenatal exposure to these medications, including birth weight,” said Jakob Christensen, M.D., DSc, Ph.D., lead author of the study and a medical consultant at Aarhus University Hospital, Denmark. “The antiseizure medication that is most effective in preventing seizures and the safest for the fetus depends heavily on the woman’s response to treatment and whether it’s possible to switch medications before the pregnancy.”
The researchers analyzed the records of infants born to 4,494,920 women in Denmark, Finland, Iceland, Norway or Sweden between 1996 and 2017 who had taken an ASM during pregnancy. They compared the birth weight of those infants to infants whose mothers had not taken an ASM. They determined lamotrigine (taken by 8,760 women) was associated with higher birth weight. Phenytoin (80 women) also was associated with higher birth weight but because it can cause birth defects, it is rarely used during pregnancy. The researchers found carbamazepine (3,420 women), oxcarbazepine (1,590 women) and topiramate (640 women) were associated with low birth weight and increased risk of being born small for gestational age.
“For most of the drugs ― especially the newer ones ― the evidence is low because few women have used them during pregnancy, meaning we found no significant association of low birth weight because only a few infants have been exposed and therefore, they cannot be considered safe,” said Dr. Christensen. “However, for drugs like lamotrigine where we have a high number of exposed children, the finding of no association with low birth weight is reassuring, indicating the drug is safe.”