To the Editor In a cohort study, Dr Huybrechts and colleagues found that maternal use of selective serotonin reuptake inhibitors (SSRIs) in late pregnancy was associated with a potential increased risk of persistent pulmonary hypertension of the newborn (PPHN). The source cohort was restricted to women with a depression diagnosis, and a logistic regression analysis was used to estimate the odds ratios for PPHN associated with antidepressant exposure. However, the authors decided not to adjust for cesarean delivery because it has been shown that conditioning on such an intermediate perinatal factor is susceptible to overadjustment bias.