This review focuses on the research concerning the relation between psychosocial factors and pregnancy outcome. The following four outcome measures are dealt with: (1) birth weight, (2) preeclampsia, (3) preterm labour, and (4) intrapartum complications. The most consistent finding concerns the association between maternal exposure to taxing situations and preterm delivery. Three possible pathways are hypothesized: (1) an indirect influence via unhealthy coping and life style behaviour, (2) a direct influence via stress-dependent hormones, and (3) an additional direct influence via psycho-immunological factors. Intervention studies aimed at improving pregnancy outcome show fairly mixed results. It is recommended that studies on the relationship between psychosocial factors and pregnancy outcome should employ a prospective design with due attention to chronic stressors, should include appropriate biochemical assessments, and multivariate techniques are applied.