Recently, the North American AED Pregnancy Registry, located at Massachusetts General Hospital in Boston, Massachusetts, found that infants who are exposed to lamotrigine as monotherapy during pregnancy (lamotrigine was used as the only AED by the mother) have a much higher risk of having an oral cleft problem, than infants born to women in a comparison group and who were not exposed to lamotrigine during pregnancy. Oral cleft problems are birth defects that may involve the lip (cleft lip), the palate (cleft palate), or both. During pregnancy, the normal openings between the upper lip and the nose (seen with cleft lip) or between the roof or back of the mouth and the nose (seen in cleft palate) may not close properly. These problems can often be seen with ultrasound testing and can usually be corrected after birth with surgery.

In this study, of 564 women who received lamotrigine alone, 5 instances of isolated cleft lip or palate (not seen as part of any specific syndrome) were seen in the babies. This data gives a prevalence rate of 8.9 per 1000, which means that oral cleft problems may occur in 8.9 of 1000 women treated with lamotrigine monotherapy. This number is 24 times higher than the risk of oral cleft problems seen in babies from the comparison group used in the study.

This information should be interpreted with caution and further analysis is underway. Women taking lamotrigine should talk to their doctors if they become pregnant or are considering pregnancy, and discuss the risks and benefits of taking lamotrigine during pregnancy. The manufacturer of Lamictal, the brand name version of lamotrigine, has stated that "Lamictal should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus".

Women who are interested in participating in pregnancy registries , may enroll themselves in the North American AED Pregnancy Registry by calling 1-888-233-2334.

The U.S. Food and Drug Administration (FDA) lists Lamictal in Pregnancy Category C. This indicates that caution is advised, but the benefits of the medication may outweigh the potential risks. So far there is no indication that Lamictal causes serious birth defects, but there have been no well-controlled studies in women, and studies in animals have shown some harm to the fetus.

The risk of birth defects is higher for women who take more than one AED and for women with a family history of birth defects.

Women who are capable of becoming pregnant should take at least 400 mcg (0.4 mg) of folic acid (folate) daily to help prevent a type of birth defect called a neural tube defect. (The best-known of these is spina bifida, in which the spinal cord is not completely enclosed.) Women at high risk, such as those with a history of this kind of defect in a previous pregnancy, should take 4000 mcg (4 mg) daily, beginning before they become pregnant. Whether folic acid is effective in preventing defects has not been proven, however, so the doctor may recommend a check-up using ultrasound during the 18th to 20th week of pregnancy.

About 20% to 35% of women have seizures more often during pregnancy because of changes in hormones or changes in how their seizure medicine is handled by the body. This appears to be particularly true for Lamictal. Therefore, the doctor may recommend checking the level of Lamictal in the blood regularly during pregnancy so that the dosage can be adjusted as needed.

Women taking Lamictal who are considering breast-feeding should discuss their options with the doctor. The baby will get some Lamictal through the milk, and its possible effects are unknown. For this reason, breast-feeding while taking Lamictal is not recommended.