The early course and antecedents of postpartum anxiety are unknown. This study sought to determine the course and antecedents of maternal anxiety during the first month postpartum and to develop a model to predict 1-month anxiety using information obtainable before perinatal hospital discharge. Two hundred and ninety-six mothers were screened before discharge with the State (SS) and Trait (TS) Scales of the State Trait Anxiety Inventory (STAI). Demographic characteristics were assessed by questionnaire and medical record review, and psychiatric history, measures of perinatal stress, and resilient factors were determined by focused questions and formal instruments. At 1-month postpartum, the SS was repeated. Scores on the SS were significantly higher at 1 month than immediately postpartum (35.30±0.68 versus 33.38±0.60, mean±standard error, P=.004), but only 58.6% of mothers with high pre-discharge anxiety had high anxiety at 1 month. One-month anxiety correlated with pre-discharge SS and TS scores, a history of psychiatric problems including depressed mood, medical and negative social life events, lack of pregnancy planning and prenatal class attendance, perceived peripartum stress, and duration of postpartum hospital stay. Inverse correlations were observed with education, household income, and resiliency factors. In multivariate modeling, anxiety trait, education, history ≥2 years of depression, and perception of peripartum stress accounted for 50% of the variance in the 1-month SS score. Maternal anxiety increases during the first postpartum month. Women with high trait anxiety, low education, a history of depressed mood, and a perception of high peripartum stress are at risk for experiencing anxiety at this time. Depression and Anxiety. © 2007 Wiley-Liss, Inc.