Lithium Exposure During Pregnancy Linked To Increased Risk of Heart Defects: Study

The use of lithium during pregnancy may increase the risk of a baby being born with serious heart defects, according to the findings of a new study. 

Lithium-based medications, such as Lithane or Lithobid, are often used to treat manic episodes of bipolar disorder, and other forms of mania. However, researchers with Harvard and Brigham and Women’s Hospital in Boston warn that when the drugs are taken during the first trimester of pregnancy, it may increase the risk of cardiac malformations.

In a study published last week in the New England Journal of Medicine, researchers noted that there have long been concerns that lithium exposure during pregnancy was linked to overall congenital heart defects; particularly Ebstein’s anomaly, a right ventricular outflow tract obstruction defect. However, the researchers said that data had been “conflicting and limited.”

To get a clearer picture, researchers conducted a cohort study that involved 1,325,563 pregnancies where women delivered a live-born infant from 2000 to 2010. All of the women were enrolled in Medicaid.

Researchers looked at the risks of heart defects among infants who were exposed during the first trimester, comparing those to infants who were unexposed or who were exposed to another mood stabilizer known as lamotrigine.

According to the findings, the overall risk of cardiac malformations among infants whose mothers used lithium during the first trimester was 65% higher than unexposed infants. What’s more, that risk appeared to be dose-specific, with only an 11% increased risk if the mother used a daily dose of 600 mg or less; a 60% increased risk if the dose was 601 mg to 900 mg, and the risk was more than tripled if the dose was 900 mg or higher.

Researchers also found that Ebstein’s anomaly occurred in 0.6% of children exposed to lithium, compared to only occurring in 0.18% of unexposed infants. The findings did not change significantly when the researchers compared infants exposed to lithium with those exposed to lamotrigine.

“Maternal use of lithium during the first trimester was associated with an increased risk of cardiac malformations, including Ebstein’s anomaly,” the researchers noted. However, they did determine that the magnitude of the effect of lithium exposure appeared to be smaller than what some previous studies had found.