Postpartum depression (PPD) affects 10-15% of all women in the perinatal period and 30-50% of women with a history of previous depression or bipolar disorder (mania and depression). Emerging evidence indicates a key role of affective cognition for the risk of PPD, including negative cognitive bias in perception of and emotional reactivity to infant signals of emotion. Interventions targeting negative bias in affective cognition may potentially reduce the risk of PPD and improve mothers' ability to detect and respond sensitively to their infants' emotions. We therefore developed and piloted a Prenatal Affective Cognitive Training (PACT) intervention targeting modulation of attentional processing, negative cognitive bias, improvement of sensitive infant directed facial expressions and emotion regulation abilities. PACT includes 'biofeedback' technology whereby real-time eye-tracking and analyses of facial expressions are used to monitor participants' responses to emotional infant signals and continuously provide feedback based on these responses. The overall aim of this randomized controlled trial is to investigate the potential prophylactic effects of the PACT intervention during pregnancy for women at heightened risk of PPD.