Antibiotic Use in Late Preterm and Full-Term Newborns.

IMPORTANCE: Antibiotic treatment saves lives in newborns with early-onset sepsis (EOS), but unwarranted antibiotic use is associated with resistant bacteria and adverse outcomes later in life. Surveillance is needed to optimize treatment strategies.

OBJECTIVE: To describe antibiotic use in association with the incidence and mortality from EOS among late-preterm and full-term newborns.

DESIGN, SETTING, AND PARTICIPANTS: The Sweden Neonatal Antibiotic Use study was a nationwide observational study that included all late-preterm and full-term neonates born from January 1, 2012, to December 31, 2020, in neonatal units of all levels. All hospital live births from 34 weeks' gestation during the study period were included in the study. Data were collected from the Swedish Neonatal Quality Register and the Swedish Medical Birth Register. Data were analyzed from August 2022 to May 2023.

EXPOSURE: Admission for neonatal intensive care during the first week of life.

MAIN OUTCOMES AND MEASURES: The main outcomes were the usage of intravenous antibiotics during the first week of life, the duration of antibiotic therapy, the rate of culture-proven EOS, and mortality associated with EOS.

RESULTS: A total of 1 025 515 newborns were included in the study; 19 286 neonates (1.88%; 7686 girls [39.9%]; median [IQR] gestational age, 40 [38-41] weeks; median [IQR] birth weight, 3610 [3140-4030] g) received antibiotics during the first week of life, of whom 647 (3.4%) had EOS. The median (IQR) duration of antibiotic treatment in newborns without EOS was 5 (3-7) days, and there were 113 antibiotic-days per 1000 live births. During the study period there was no significant change in the exposure to neonatal antibiotics or antibiotic-days per 1000 live births. The incidence of EOS was 0.63 per 1000 live births, with a significant decrease from 0.74 in 2012 to 0.34 in 2020. Mortality associated with EOS was 1.39% (9 of 647 newborns) and did not change significantly over time. For each newborn with EOS, antibiotic treatment was initiated in 29 newborns and 173 antibiotic-days were dispensed.

CONCLUSIONS AND RELEVANCE: This large nationwide study found that a relatively low exposure to antibiotics is not associated with an increased risk of EOS or associated mortality. Still, future efforts to reduce unwarranted neonatal antibiotic use are needed.