Bipolar illness can be particularly difficult to manage in pregnancy and during the post-partum period. The risks of mood stabilizing medication on the health of the infant must be considered carefully along with the risks of uncontrolled illness in the mother. Lithium use in pregnancy and lactation has been associated with a number of negative effects in the newborn. This article reviews the latest evidence regarding the risks and benefits of the use of lithium in pregnant or lactating women.