© 2018 Walter de Gruyter GmbH, Berlin/Boston. To determine the frequency of sepsis and other adverse neonatal outcomes in women with a clinical diagnosis of chorioamnionitis. We performed a secondary analysis of a multi-center placebo-controlled trial of vitamins C/E to prevent preeclampsia in low risk nulliparous women. Clinical chorioamnionitis was defined as either the "clinical diagnosis" of chorioamnionitis or antibiotic administration during labor because of an elevated temperature or uterine tenderness in the absence of another cause. Early-onset neonatal sepsis was categorized as "suspected" or "confirmed" based on a clinical diagnosis with negative or positive blood, urine or cerebral spinal fluid cultures, respectively, within 72 h of birth. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression. Data from 9391 mother-infant pairs were analyzed. The frequency of chorioamnionitis was 10.3%. Overall, 6.6% of the neonates were diagnosed with confirmed (0.2%) or suspected (6.4%) early-onset sepsis. Only 0.7% of infants born in the setting of chorioamnionitis had culture-proven early-onset sepsis versus 0.1% if chorioamnionitis was not present. Clinical chorioamnionitis was associated with both suspected [OR 4.01 (3.16-5.08)] and confirmed [OR 4.93 (1.65-14.74)] early-onset neonatal sepsis, a need for resuscitation within the first 30 min after birth [OR 2.10 (1.70-2.61)], respiratory distress [OR 3.14 (2.16-4.56)], 1 min Apgar score of ≤3 [OR 2.69 (2.01-3.60)] and 4-7 [OR 1.71 (1.43-2.04)] and 5 min Apgar score of 4-7 [OR 1.67 (1.17-2.37)] (vs. 8-10). Clinical chorioamnionitis is common and is associated with neonatal morbidities. However, the vast majority of exposed infants (99.3%) do not have confirmed early-onset sepsis.