Exploring Lithium Concentrations in Maternal blood, Amniotic fluid and Umbilical cord blood: Babies Born to Mothers Treated with Lithium Carbonate for Bipolar Disorder

Introduction: The distribution of lithium in amniotic fluid, maternal blood, and umbilical cord blood during pregnancy is poorly understood. Additionally, there is a need to describe neonatal complications observed among mothers using lithium for the treatment of bipolar disorder. Methods: In an observational case-series study, we identified 37 pregnancies from 31 women with bipolar disorder who underwent lithium treatment throughout gestation from 2011 to 2018. We compared lithium levels in maternal blood, umbilical cord blood, and amniotic fluid using a mixed effects model. Additionally, we described the occurrence of maternal polyhydramnios and neonatal complications observed in our cohort. Results: Mean lithium concentrations were 1.03 mM in amniotic fluid, 0.50 mM in umbilical cord blood, and 0.61 mM in maternal blood. Amniotic fluid exhibited significantly higher lithium levels compared to maternal blood (mean difference: 0.39 mM, 95% confidence Interval: [0.19-0.58], p<0.001). Conclusion: Amniotic fluid had higher lithium levels than maternal blood, while umbilical cord blood levels were similar, suggesting that amniotic fluid accumulates lithium during pregnancy. Our study highlights potential complications for pregnant women with bipolar disorder using lithium, identifying important outcomes of concern for future research.