A sample size calculation was performed. Based on an anticipated rate of postpartum depression (PPD) of 30% in the placebo group, we would need 62 subjects in each group to detect a reduction in PPD to 10% in the sertraline group, with a power of .8 and a Type I error of .05. Based on the 2200 deliveries occurring annually at Cooper University Hospital, we anticipate that it would take 2-3 years to recruit 124 subjects into this study.