Where possible, the use of medications during the perinatal period should be limited to monotherapy. Women with BD often have complex medication regimens before conception, especially in cases of more severe or treatment-resistant illness. Studies of fetal risk associated with mood stabilizer polytherapy are lacking. However, one study showed higher rates of congenital anomalies with polytherapy compared to monotherapy for the treatment of epilepsy (Holmes et al. 2011). Another study showed higher rates of adverse outcomes for both the mother and fetus when antipsychotics were combined with other psychotropic medications compared to antipsychotic monotherapy (Sadowski etal. 2013). Another factor con­tributing to the complexity of antenatal BD management has been a lack of consis­tency in the ndings of adverse fetal outcomes attributed to different mood-stabilizing medications. Most systematic reviews and meta-analyses of fetal risks associated with antipsychotics have looked at the medication as a group rather than separating out data for individual antipsychotics (Coughlin etal. 2015). Studies of fetal risk using information from population-based databases may have signicant confound­ing factors that are co-morbid to the psychiatric disorder being treated, such as higher rates of substance abuse, poorer physical health, and poorer access to prena­tal care. BD itself may have a teratogenic risk as it has been associated with higher rates of microcephaly and neonatal hypoglycemia in offspring (Boden etal. 2012). Yet, an overall understanding of the risks that the illness itself poses to pregnancy is inadequate.