Increasing numbers of patients are being treated for mood disorders. The majority of these patients, particularly with the diagnosis of major depression, are women of childbearing years. Concerns about fetal exposure to medication, both planned and unplanned, are becoming more pressing in the clinical practices of both psychiatrists and primary care physicians. There are relatively few study data available to guide clinicians in the use of psychotropic medications during pregnancy because of obvious problems in designing studies of the effects of medication on pregnant women, fetuses, and infants. Clinicians in all specialties receive little or no formal training in this area of psychopharmacology. This article gathers clinically relevant studies and practice information and provides suggestions regarding the approach to treatment of mood disorders during pregnancy, based on a risk assessment model.