BACKGROUND: Recently, ACOG released updated definitions for intraamniotic infection (IAI): maternal fever (≥38.0 °C) and ≥1 symptom (fetal tachycardia, maternal white blood cell count >15,000/mm3 or purulent discharge). Treatment was no longer recommended for women with fever <39.0 °C plus maternal tachycardia or fundal tenderness (previous criteria). The objective of this study was to compare postpartum infectious morbidity among women meeting previous criteria (but not the new IAI criteria) to women meeting new IAI criteria. METHODS: Retrospective cohort of women delivering vaginally at a single academic center. Demographics, antepartum and intrapartum characteristics of women who met diagnostic criteria for chorioamnionitis (previous criteria) compared to those who met IAI criteria using bivariate statistics. The primary outcome was a composite of postpartum infection, including: endometritis, perineal infection, sepsis, urinary tract infection, pyelonephritis. Backward-stepwise elimination used to estimate odds of primary outcome. RESULTS: Of 229 women who met previous IAI criteria, 51 (22.3%) did not meet new IAI criteria. Women no longer meeting IAI criteria were younger (25 versus 27 years, p = .02), more likely to have gestational hypertension (16.0 versus 3.4%, p < .01), and less likely to have third or fourth degree lacerations (2.0 versus 13.4%, p = .02). No difference in antibiotic receipt was observed. Postpartum infection occurred in 16/229 (7.0%) women overall; five (9.8%) in those not meeting new IAI criteria, and 11 (6.2%) meeting new IAI criteria. After adjusting for confounders, there was no difference in odds of postpartum infection (aOR 1.65, 95% CI 0.55-4.99). CONCLUSIONS/IMPLICATIONS: Among women who met old ACOG criteria for IAI, but not the new criteria, postpartum infection occurred in nearly 10%. This number could be higher if these women were not treated with antibiotics.