Objective: To follow mothers' mood through pregnancy and after childbirth and compare reported symptoms of depression at each stage. Design: Longitudinal cohort study. Setting: Avon. Participants: Pregnant women resident within Avon with an expected date of delivery between 1 April 1991 and 31 December 1992. Main outcome measures: Symptom scores from the Edinburgh postnatal depression scale at 18 and 32 weeks of pregnancy and 8 weeks and 8 months postpartum. Proportion of women above a threshold indicating probable depressive disorder. Results: Depression scores were higher at 32 weeks of pregnancy than 8 weeks postpartum (difference in means 0.88, 95% confidence interval 0.79 to 0.97). There was no difference in the distribution of total scores or scores for individual items at the four time points. 1222 (13.5%) women scored above threshold for probable depression at 32 weeks of pregnancy, 821 (9.1%) at 8 weeks postpartum, and 147 (1.6%) throughout. More mothers moved above the threshold for depression between 18 weeks and 32 weeks of pregnancy than between 32 weeks of pregnancy and 8 weeks postpartum. Conclusions: Symptoms of depression are not more common or severe after childbirth than during pregnancy. Research and clinical efforts need to be moved towards understanding, recognising, and treating antenatal depression.

Some small studies suggest that maternal postnatal depression is a risk factor for offspring adolescent depression. However, to our knowledge, no large cohort studies have addressed this issue. Furthermore, only 1 small study has examined the association between antenatal depression and later offspring depression. Understanding these associations is important to inform prevention. To investigate the hypothesis that there are independent associations between antenatal and postnatal depression with offspring depression and that the risk pathways are different, such that the risk is moderated by disadvantage (low maternal education) with postnatal depression but not with antenatal depression. Prospective investigation of associations between symptoms of antenatal and postnatal parental depression with offspring depression at age 18 years in a UK community-based birth cohort (Avon Longitudinal Study of Parents and Children) with data from more than 4500 parents and their adolescent offspring. Diagnosis of offspring aged 18 years with major depression using the International Classification of Diseases, 10th Revision. Antenatal depression was an independent risk factor. Offspring were 1.28 times (95% CI, 1.08-1.51; P = .003) more likely to have depression at age 18 years for each standard deviation increase in maternal depression score antenatally, independent of later maternal depression. Postnatal depression was also a risk factor for mothers with low education, with offspring 1.26 times (95% CI, 1.06-1.50; P = .01) more likely to have depression for each standard deviation increase in postnatal depression score. However, for more educated mothers, there was little association (odds ratio, 1.09; 95% CI, 0.88-1.36; P = .42). Analyses found that maternal education moderated the effects of postnatal but not antenatal depression. Paternal depression antenatally was not associated with offspring depression, while postnatally, paternal depression showed a similar pattern to maternal depression. The findings suggest that treating maternal depression antenatally could prevent offspring depression during adulthood and that prioritizing less advantaged mothers postnatally may be most effective.