Perinatal depression is an important problem with potentially deleterious health outcomes; however, we know little about the trajectories of depression and treatment.

We report the patterns of maternal depression and trajectories of treatment response in early and late pregnancy and during postpartum in 649 women recruited from the general population of pregnant women in Western Canada. Women who scored ≥ 12 on the Edinburgh Postnatal Depression Scale were classified as depressed.

Fifty-two percent of participants were primiparas, 90% were partnered, 83.3% Caucasian, 67% earn more than $40,000 per year, 90% completed high school, and 77% had planned pregnancy. The unadjusted prevalence of depression in early pregnancy (17 weeks) was 14%, late pregnancy (30 weeks) 11.5%, and postpartum (4.1 weeks) was 9.8%. All of the psychosocial factors measured - history of depression, mood instability, lack of social support, relationship problems, worry, and stressors heighten depression symptoms throughout parturition. Our practice of referring women who screened positive for depression changed prevalence rates of women who were depressed and in treatment. The number of women in treatment increased from 12.2% in early pregnancy to 24.8% at postpartum. Women were significantly more likely to get symptom relief counselling in pregnancy compared to psychotropic medication use in postpartum, with the exception of those women with history of depression and treatment engagement.

Increased understanding of the patterns and nature of maternal depression and treatment response is essential to early identification of women who are depressed and lead to treatment that is more effective.