The present study compared the impact of maternal major depression, anxiety disorders and their comorbidities on gestational age and birth weight of infants.A total of 1119 women consisting of 26 women with only major depression, 125 women with only anxiety disorder, 36 women with major depression plus an anxiety disorder and 932 women without any psychiatric disorders were included in the study. Psychiatric diagnoses were determined by means of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition.The comorbid group had the highest proportion of newborns with preterm birth and low birth weight. Moreover, these newborns had the lowest birth weight and gestational age.Cross-sectional study design.The study results suggest that comorbidity between major depression and anxiety disorders during pregnancy may have noteworthy negative effects on birth weight and gestational age.