Project Summary There is an increase in psychotropic medication use in women in their fertile ages. Due to concerns for the developing fetus, half of women decide to discontinue their medication before- or at the beginning of pregnancy. While the wish to avoid in utero medication exposure to the fetus is understandable, discontinuation of medication might lead to relapse, which can have a profound negative impact on the health of mother and child. In our prior R01, we showed that relapse risks were relatively limited for women with unipolar depression who chose to discontinue their antidepressant medication before or during pregnancy. In addition, we found limited risks for those women who choose to continue their antidepressants as we found a small increase in the risk of short- term but not long-term outcomes associated with antidepressant exposure for offspring. While our findings greatly help in weighting risks and benefits for women with unipolar disorders, there is an urgent need to investigate risks in women with bipolar disorders, given that these women are at very well high risk of severe relapse in the perinatal period which can lead to suicide or infanticide. Currently, antipsychotic medication (AP) is the most used treatment option in bipolar patients during the perinatal period but data on the efficacy of AP in preventing perinatal relapse is completely lacking. Moreover, both short- and long-term effects of AP on maternal and offspring health are insufficiently known. In this renewal, we propose to investigate the risks and benefits of antipsychotic use during pregnancy for women with bipolar disorder and their offspring. We will use large and comprehensive Danish and Swedish population-based registers and with this sample size, we will be able to investigate efficacy of Antipsychotics (AP) in prevention of relapse in bipolar women the perinatal period (aim 1); we will investigate adverse short and long term maternal health outcomes of both relapse and/or AP use (aim 2). In our last aim we will determine the long-term effects (up to 24 years) of maternal relapse during pregnancy and the postpartum period on the offspring and the effects of in utero AP exposure on the offspring (aim 3). .