Abstract: We included two randomised controlled trials. One trial compared oral 100 microgram (µg) selenium yeast tablets with placebo, taken from the first trimester until birth. The trial randomised 179 women but outcome data were only provided for 85 women. Eighty-three women were randomised to each arm of the trial. Sixty-one women completed the selenium arm, 44 of whom completed an Edinburgh Postnatal Depression Scale (EPDS). In the placebo arm, 64 women completed the trial, 41 of whom completed an EPDS. This included study (n = 85) found selenium had an effect on EPDS scores but did not reach statistical significance (P = 0.07). There was a mean difference (MD) of -1.90 (95% confidence interval (CI) -3.92 to 0.12) of the self-reported EPDS completed by participants within eight weeks of delivery. There was a high risk of attrition bias due to a large proportion of women withdrawing from the study or not completing an EPDS. This included study did not report on any of the secondary outcomes of this review. The other trial compared docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) with placebo. The trial randomised 126 women at risk of postpartum depression to three arms: 42 were allocated to EPA, 42 to DHA, and 42 to placebo. Three women in the EPA arm, four in the DHA arm, and one woman in the placebo arm were lost to follow-up. Women who were found to have major depressive disorder, bipolar disorder, current substance abuse or dependence, suicidal ideation or schizophrenia at recruitment were excluded from the study. The women who discontinued the intervention (five in the EPA arm, four in the DHA arm and seven in the placebo arm) were included in the intention-to-treat analysis, while those who were lost to follow-up were not. Women received supplements or placebo from recruitment at a gestational age of 12 to 20 weeks until their final review visit six to eight weeks postpartum. The primary outcome measure was the Beck Depression Inventory (BDI) score at the fifth visit (six to eight weeks postpartum). No benefit was found for EPA-rich fish oil (MD 0.70, 95% CI -1.78 to 3.18) or DHA-rich fish oil supplementation (MD 0.90, 95% CI -1.33 to 3.13) in preventing postpartum depression. No difference was found in the effect on postnatal depression comparing EPA with DHA (MD -0.20, 95% CI -2.61 to 2.21). No benefit or significant effect was found in terms of the secondary outcomes of the presence of major depressive disorder at six to eight weeks postpartum, the number of women who commenced antidepressants, maternal estimated blood loss at delivery or admission of neonates to the neonatal intensive care unit. There is insufficient evidence to conclude that selenium, DHA or EPA prevent postnatal depression. There is currently no evidence to recommend any other dietary supplement for prevention of postnatal depression.

Plain-language summary: This review identified two randomised controlled studies. One study examined the effect of selenium supplements taken by women from the first trimester to birth in preventing postnatal depression. This study had a high risk of bias because of women withdrawing or not completing their self-scoring system for depression (Edinburgh Postnatal Depression Scale). It may also have been difficult to ensure that the women took their supplements because of concerns that exist about taking supplements during pregnancy. More high-quality studies would be required to confirm any benefit in preventing postnatal depression using selenium. This review also identified one randomised controlled study that compared docosahexanoic and eicosapentaenoic acid to placebo in women at risk of postpartum depression. This study found that neither docosahexanoic acid nor eicosapentaenoic acid prevented postpartum depression. Overall, there is not enough evidence at this stage to recommend selenium, docosahexanoic acid, eicosapentaenoic acid or any other dietary supplement for the prevention of postnatal depression. Unfortunately there were no other studies of other dietary supplements that met our selection criteria. Other dietary supplements need to be studied in trials where depressed women are excluded from entry to determine if supplements prevent postnatal depression.