BackgroundDepression in pregnancy negatively affects maternal-child health. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation treatment for depression, has not been evaluated in pregnancy. ObjectiveTo conduct a pilot randomized controlled trial (RCT) to evaluate tDCS for antenatal depression. MethodsIn this pilot RCT in Toronto, Ontario (October 2014 to December 2016), adult pregnant women 14–32 weeks gestation with major depressive disorder who had declined antidepressant medication were considered for inclusion. Participants were randomly assigned 1:1 to tDCS or sham-control. Active tDCS comprised 30-min sessions of 2 mAmp direct current delivered over the dorsolateral prefrontal cortex, 5 days per week, for 3 weeks. Sham was administered similarly, but with current turned off after 30 s. Main outcomes were feasibility, acceptability, and protocol adherence. Maternal Montgomery Asperg Depression Rating Scale (MADRS) was measured post-treatment and at 4 and 12 weeks postpartum. ResultsOf 20 women randomized, 16 completed treatment and provided data (124 tDCS, 122 sham sessions). Views of treatment were positive with no serious adverse events. Post-treatment estimated marginal mean MADRS scores were 11.8 (standard error, SE 2.66) for tDCS and 15.4 (SE 2.51) for sham (p = 0.34). At 4 weeks postpartum, 75.0% of tDCS women were remitted versus 12.5% sham-control (p = 0.04). ConclusionsResults support proceeding to a definitive RCT to evaluate tDCS for antenatal depression. The preliminary efficacy estimates immediately post-treatment and in the postpartum, are encouraging with respect to the potential use of tDCS to improve treatment rates in this population. The trial was registered at: clinical trials.gov (NCT02116127).