Background: Giving birth in a health care facility does not guarantee high-quality care or favorable outcomes. The working-hour phenomenon describes adverse outcomes of institutional births outside regular working hours.
Objectives: The objectives of the study were to evaluate whether the time of birth is associated with adverse neonatal outcomes and to identify the riskiest time periods for obstetrical care.
Study design: This nationwide retrospective cohort study analyzed data from 2008 to 2016 from all 82 obstetric departments in Austria. Births at ≥ 23+0 gestational weeks with ≥500 g birthweight were included. Independent variables were categorized by the time of day vs night as core time (morning, day) and off hours (evening, nighttime periods 1-4). The composite primary outcome was adverse neonatal outcome, defined as arterial umbilical cord blood pH <7.2, 5 minute Apgar score <7, and/or admission to the neonatal intensive care unit. Multivariate logistic regression was used to develop a model to predict these adverse neonatal outcomes.
Results: Of 462,947 births, 227,672 (49.2%) occurred during off hours and had a comparable distribution in all maternity units, regardless of volume (<500 births per year: 50.3% during core time vs 49.7% during off hours; ≥500 births per year: 50.7% core time vs 49.3% off hours; perinatal tertiary center: 51.2% core time vs 48.8% off hours). Furthermore, most women (35.8-35.9%) gave birth between 2:00 and 5:59 am (night periods 3 and 4). After adjustment for covariates, we found that adverse neonatal outcomes also occurred more frequently during these night periods 3 and 4, in addition to the early morning period (night 3: odds ratio, 1.05; 95% confidence interval, 1.03-1.08; P < .001; night 4: odds ratio, 1.08; 95% confidence interval, 1.05-1.10; P < .001; early morning period: odds ratio, 1.05; 95% confidence interval, 1.02-1.08; P < .001). The adjusted odds for adverse outcomes were lowest for births between 6:00 and 7:59 pm (odds ratio, 0.96; 95% confidence interval, 0.93-0.99; P = .006).
Conclusion: There is an increased risk of adverse neonatal outcomes when giving birth between 2:00 and 7:59 am. The so-called working-hour phenomenon is an attainable target to improve neonatal outcomes. Health care providers should ensure an optimal organizational framework during this time period.
Keywords: adverse neonatal outcome; circadian rhythm; neonatal acidemia; neonatal intensive care unit; neonatal morbidity; neonatal mortality; obstetrics; parturition; pregnancy outcome; working-hour phenomenon.
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