Postpartum depression is a major mental health issue for women and society. We examined stability and change in symptoms of depression over two consecutive pregnancies and tested life stress as a potential mechanism. The Community Child Health Network followed an ethnically/racially diverse sample from one month after a birth for two years. A subset of 228 women had a second birth. Interview measures of depression symptoms (EPDS) and life stress (life events, perceived stress, chronic stress, interpersonal aggression) were obtained during home visits. Three-quarters of the sample showed intra-individual stability in depressive symptoms from one postpartum period to the next, and 24% of the sample had clinically significant symptoms after at least one pregnancy (9% first, 7.5% second, 3.5% both). Each of the four life stressors significantly mediated the association between depressive symptoms across two postpartum periods. Stress between pregnancies for women may be an important mechanism perpetuating postpartum depression
