Background The course of depression from pregnancy to 1 year post partum and risk factors among mothers and fathers are not known.

Aims (1) To report the longitudinal patterns of depression from the third trimester of pregnancy to 1 year after childbirth; (2) to determine the gender differences between women and their partners in the effect of psychosocial and personal factors on postpartum depression.

Methods A longitudinal cohort study was carried out over a consecutive sample of 769 women in their third trimester of pregnancy and their partners attending the prenatal programme in the Valencian Community (Spain) and follow-up at 3 and 12 months post partum. The outcome variable was the presence of depression at 3 or 12 months post partum measured by the Edinburgh Postnatal Depression Scale. Predictor variables were: psychosocial (marital dissatisfaction, confidant and affective social support) and personal (history of depression, partner's depression and negative life events, depression during the third trimester of pregnancy) variables. Logistic regression models were fitted via generalised estimating equations.

Results At 3 and 12 months post partum, 9.3% and 4.4% of mothers and 3.4% and 4.0% of fathers, respectively, were newly diagnosed as having depression. Low marital satisfaction, partner's depression and depression during pregnancy increased the probability of depression during the first 12 months after birth in mothers and fathers. Negative life events increased the risk of depression only among mothers.

Conclusions Psychosocial and personal factors were strong predictors of depression during the first 12 months post partum for both mothers and fathers.