Background: Lithium is predominantly used in severe mood disorders, most notably bipolar disorder. Due to the chronic nature of these disorders, lithium treatment may be continued in pregnancy. However, there is limited information on its use around pregnancy.
Objectives: To describe the utilization of lithium before, during and after pregnancy, including trends in prevalence and characteristics of users, in the five Nordic countries.
Methods: Data sources included individually linked data from the nationwide health registers in Denmark (2000-2021), Finland (2005-2016), Iceland (2004-2017), Norway (2005-2020), Sweden (2006-2019). The prevalence of lithium use in each country was calculated as the proportion of pregnancies in which women filled ≥1 prescription of lithium from three months before the first day of the last menstrual period to birth. For the women using lithium, we described secondary care diagnostic codes related to lithium treatment recorded in the year before and during pregnancy and prescription fills of other psychotropic medications in the three months before and during pregnancy. Additionally, patterns of use by the three months before pregnancy (PRE), trimesters (T1-T3), and the three months after childbirth (POST) were examined.
Results: The prevalence of lithium use in 4,556,273 pregnancies was 0.04% (n = 2,032) and varied from 0.02% (Finland) to 0.08% (Iceland). Lithium use increased in the study countries, from 0.02% in 2006 to 0.06% in 2016. Among women with lithium use in pregnancy 81% had a diagnosis of bipolar disorder, 13% recurrent depressive disorder, and 3% schizoaffective disorder. Further, 26% had ≥1 prescription fill of an antiepileptic, 44% of an antipsychotic, and 44% of an antidepressant. Prescription fills for lithium became less common in later trimesters compared to the three months before pregnancy, with an increase in the post-partum period (PRE: 1,571, T1: 1,251, T2: 1,018, T3: 923, POST: 1,383).
Conclusions: From 2006 to 2016, lithium use in pregnancy became three times more prevalent in the Nordic countries. Bipolar disorder was the most common diagnosis among women using lithium in pregnancy, and other indications for lithium were comparatively rare. Furthermore, concurrent use of other psychotropic medications was common. Some women may discontinue lithium treatment before or during pregnancy, and may re-initiate after childbirth.
