Although the postpartum period has typically been considered a period of risk for relapse of bipolar disorder, systematic data regarding the course of bipolar disorder during pregnancy is essentially unknown. The management of bipolar women who plan to conceive or who are pregnant poses significant challenges for clinicians who care for these patients. Recent data suggest that pregnancy is not protective and the risk for relapse after lithium discontinuation is similar in pregnant and nonpregnant women with 50 percent relapsing within 6 months. This article reviews the major clinical dilemmas in managing pregnant bipolar patients and recent data on the course of bipolar disorder during pregnancy. Treatment guidelines are presented.