Leisure-Time Physical Activity in Pregnancy and Risk of Postpartum Depression: A Prospective Study in a Large National Birth Cohort

Objective: To explore the association between physical activity during pregnancy and postpartum depression (PPD) in a large, prospective cohort.

Method: Exposure information from the Danish National Birth Cohort, a large, prospective cohort with information on more than 100,000 pregnancies (1996-2002), was linked to the Danish Psychiatric Central Register and the Danish Register for Medicinal Product Statistics for data on clinically identified cases of depression up to 1 year postpartum. A total of 70,866 women from the Danish National Birth Cohort were included in the analyses. Duration, frequency, and type of physical activity were assessed by a telephone interview at approximately week 12 of gestation. Admission to hospital due to depression (PPD-admission) and prescription of an antidepressant (PPD-prescription) were treated as separate outcomes.

Results: Through linkage to national registers, we identified 157 cases of PPD-admission and 1,305 cases of PPD-prescription. Women engaging in vigorous physical activity during pregnancy had a lower risk of PPD-prescription compared to women who were not physically active (adjusted odds ratio, 0.81; 95% CI, 0.66-0.99). No association was observed between physical activity and PPD-admission; but, in women who were underweight prior to pregnancy, physical activity was associated with increased risk of PPD-admission.

Conclusions: Our data are compatible with a protective effect of vigorous physical activity, but not for other measures of physical activity, against postpartum depression requiring antidepressant therapy. No protective effect could be detected on PPD leading to hospitalization.

Submitted: January 6, 2009; accepted April 8, 2009.

Corresponding author: Marin Strøm, MSc, Maternal Nutrition Group, Department of Epidemiology Research, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark (mrm@ssi.dk).