The few studies that have addressed the relationship between severity of intrapartum fever and neonatal and maternal morbidity have had mixed results. The impact of the duration between reaching maximum intrapartum temperature and delivery on neonatal outcomes remains unknown.

To test the association of severity of intrapartum fever and duration from reaching maximum temperature to delivery with neonatal and maternal morbidity.

This was a secondary analysis of a prospective cohort of term, singleton patients admitted for induction of labor or spontaneous labor who had intrapartum fever (≥38°C). Patients were divided into 3 groups according to maximum temperature during labor: afebrile (<38°C), mild fever (38°C–39°C), and severe fever (>39°C). The primary outcome was composite neonatal morbidity (umbilical artery pH <7.1, mechanical ventilation, respiratory distress, meconium aspiration with pulmonary hypertension, hypoglycemia, neonatal intensive care unit admission, and Apgar <7 at 5 minutes). Secondary outcomes were composite neonatal neurologic morbidity (hypoxic-ischemic encephalopathy, hypothermia treatment, and seizures) and composite maternal morbidity (postpartum hemorrhage, endometritis, and maternal packed red blood cell transfusion). Outcomes were compared between the maximum temperature groups using multivariable logistic regression. Cox proportional-hazards regression modeling accounted for the duration between reaching maximum intrapartum temperature and delivery.

Of the 8132 patients included, 278 (3.4%) had a mild fever and 74 (0.9%) had a severe fever. The incidence of composite neonatal morbidity increased with intrapartum fever severity (afebrile 5.4% vs mild 18.0% vs severe 29.7%; P<.01). After adjusting for confounders, there were increased odds of composite neonatal morbidity with severe fever compared with mild fever (adjusted odds ratio, 1.93 [95% confidence interval, 1.07–3.48]). Severe fevers remained associated with composite neonatal morbidity compared with mild fevers after accounting for the duration between reaching maximum intrapartum temperature and delivery (adjusted hazard ratio, 2.05 [95% confidence interval, 1.23–3.43]). Composite neonatal neurologic morbidity and composite maternal morbidity were not different between patients with mild and patients with severe fevers.

Composite neonatal morbidity correlated with intrapartum fever severity in a potentially dose-dependent fashion. This correlation was independent of the duration from reaching maximum intrapartum temperature to delivery, suggesting that clinical management of intrapartum fever, in terms of timing or mode of delivery, should not be affected by this duration.