For women with bipolar disorder who are planning a pregnancy, it is common practice to discontinue mood stabilizers prior to attempts to conceive, since the mood stabilizers most commonly used to treat bipolar disorder (lithium, valproic acid, and carbamazepine) all carry some risk of birth defect. The problem with this approach is that, after discontinuation of maintenance treatment, a woman is at very high risk for relapse. The longer it takes to get pregnant and the longer she remains off medication, the greater is her risk for having recurrent illness.
There is one approach for women who are taking lithium that may help minimize the time spent medication-free while trying to conceive. Rather than discontinuing lithium prior to attempts to conceive, the woman would quickly taper off medication after she learns she is pregnant. Usually women discover they are pregnant 2-4 weeks after conception (or 4 to 6 weeks after the last menstrual period). By this time the placenta has formed and the fetus may be exposed to medication via the placental circulation; however, exposure to lithium during the earliest stages of pregnancy is not associated with risk of birth defect. Lithium may affect the development of the fetal heart which forms 4-8 weeks after conception, and congenital heart defects occur when lithium exposure occurs during this window of vulnerability. If lithium is stopped prior to this window, the risk of heart defect is reduced.
This is not an approach suited to every woman. If your periods are irregular, it may be difficult to determine exactly when you are pregnant and the fetus may inadvertently be exposed to lithium during the window of vulnerability. There is also some concern that rapid discontinuation of lithium may increase one’s risk of relapse. If you have a very severe form of bipolar disorder, you may consider maintaining lithium during the first trimester despite the risk of birth defect.
Ruta Nonacs, MD PhD