A review published in the Journal of Affective Disorders compared the effectiveness of omega-3 polyunsaturated fatty acid supplementation on depression during pregnancy or postpartum depression (PPD) after childbirth. Researchers searched MEDLINE, PubMed, PsycINFO, and the Cochrane Collaboration Registry of Controlled Trials, etc. through July 2017. Studies of dietary intake and plasma and/or milk levels of omega-3 fatty acids and trials of benefits and effects of omega-3 fatty acids supplements on pregnant or postpartum women with depression were selected. It was stated that omega-3 fatty acid deficiency, on account of inadequate intake, or fast depletion during pregnancy and lactation, is one of the risk factors for PPD. Several studies have also reported associations between neuroinflammation (elevated pro-inflammatory cytokines) and aberrant neurotransmission (low serotonergic transmission activity) and risk of PPD. It was suggested that supplementation with eicosapentaenoic acid (EPA)-rich oil can effectively reduce depression during pregnancy and PPD after childbirth. Long-term treatment with docosahexaenoic acid (DHA)-rich oil can also be effective in reducing the risk of PPD in healthy women, but not in lactating women. Therefore, dietary supplementation with omega-3 fatty acids rich in EPA during pregnancy or postpartum tends to reduce some symptoms associated with depression. Additionally, DHA supplementation to healthy pregnant women can also reduce the risk of PPD.