Clozapine Treatment During Pregnancy and the Postpartum Period: A Systematic Literature Review

Objective: The objective of this systematic review was to provide a critical appraisal of the evidence related to the safety of clozapine for schizophrenia during pregnancy and lactation. Data Sources: PubMed/MEDLINE, Embase, and the Cochrane Library were searched from inception through December 2020. Reference lists of included studies were hand-searched. The International Clinical Trials Registry Platform and ClinicalTrials.gov were searched for unpublished trials, and PROSPERO was searched for unpublished reviews. The current marketing authorization holder of the originator brands Clozaril and Leponex was also contacted for pharmacovigilance data. Study Selection: Original reports published in English, German, French, or Dutch containing clinical and preclinical data were included if they provided data on maternal, fetal, and neonatal outcomes after clozapine exposure during pregnancy or lactation. Data Extraction: Two reviewers independently extracted relevant data. Results: A total of 860 records were identified, and the full texts of 117 articles were reviewed. Forty-two studies met the inclusion criteria. Data on perinatal clozapine exposure are of limited quality and quantity. Although clozapine demonstrates partial placental passage, data thus far do not support that clozapine is teratogenic; that it increases the risk of stillbirth, abortion, or fetal disorders; or that it increases the risk of delivery complications or premature birth. Information about clozapine exposure through breast milk is scarce, but based on its chemical properties, it is likely that clozapine enters the breast milk of nursing mothers taking clozapine. Conclusions: When weighing the risks and benefits of clozapine continuation during pregnancy and lactation versus switching to another antipsychotic, one should include severity of illness and treatment history but also be aware of the limitations of the available safety data regarding perinatal clozapine use, including the fact that there are few studies.