(550) Are maternal fever height and duration during labor associated with the risk of hypoxic-ischemic encephalopathy?

To examine if the height of fever and/or duration between maternal fever onset and delivery modifies the risk of hypoxic-ischemic encephalopathy (HIE).


Study Design:

Population-based cohort study of singleton neonates without congenital anomalies born > 35 weeks at 15 Kaiser Permanente Northern California hospitals between January 2012 and July 2019. Maternal fever was defined as at least one temperature >38°C before delivery. Maximal maternal temperature and timing of the first maternal fever were extracted from medical records. HIE was defined as the presence of both neonatal encephalopathy and perinatal acidosis (cord pH< 7 or base deficit >10 on any gas within 2 hours after birth). We evaluated the associations between maximal maternal temperature and duration between fever onset to delivery and neonatal outcomes, using Poisson regression adjusting for duration of labor as a spline.


Results:

Among 280,347 neonates, exposure to maternal fever occurred in 27,317 (9.8%) and HIE occurred in 490 (0.17%). The incidence of HIE was higher among infants of febrile compared to afebrile mothers (Relative risk - RR 4.4 [95% CI 3.6-5.3]). Both the height (Figure 1) and duration (Figure 2) of fever were associated with an increased risk of HIE. After adjusting for duration of labor, the incidence of HIE increased with each 0.1°C increase in maximal maternal temperature (Incidence rate ratio- IRR 1.09; 95% CI 1.08-1.11) and for each hour between fever onset and delivery (IRR 1.06 95%CI 1.05-1.07). 


Conclusion:

The higher the maternal fever and the longer the duration between fever onset and delivery, the higher the risk of developing HIE. Novel strategies designed to predict the risk of adverse neonatal outcomes during labor and delivery should account for these factors.