The relation between low-grade fever during prolonged rupture of membranes (>12 hours) at term and infectious outcomes: a retrospective cohort study

Background: Intrapartum fever (>38°C) is associated with adverse maternal and neonatal outcomes. However, the correlation between low-grade fever (37.5°C–37.9°C) and adverse perinatal outcomes remains controversial. Objective: This study aimed to compare maternal and neonatal outcomes of women with prolonged rupture of membranes (≥12 hours) at term between those with low-grade fever and those with normal body temperature. Study Design: This retrospective study included women hospitalized in a tertiary university-affiliated hospital between July 2021 and May 2023 with singleton term and rupture of membranes ≥12 hours. Women were classified as having intrapartum low-grade fever (37.5°C–37.9°C) or normal body temperature (<37.5°C). The co-primary outcomes, postpartum endometritis and neonatal intensive care unit admission rates, were compared between these groups. The secondary maternal outcomes were intrapartum leukocytosis (>15,000/mm²), cesarean delivery rate, postpartum hemorrhage, postpartum fever, surgical site infection, and postpartum length of stay. The secondary neonatal outcomes were early-onset sepsis, 5-minute Apgar score of <7, umbilical artery cord pH<7.2 and pH<7.05, neonatal intensive care unit admission length of stay, and respiratory distress. The data were analyzed according to rupture of membranes 12 to 18 hours and rupture of membranes ≥18 hours. In women with rupture of membranes ≥18 hours, intrapartum ampicillin was administered, and chorioamniotic membrane swabs were obtained. The likelihood ratios and 95% confidence intervals were calculated for the co-primary outcomes. A multivariate logistic regression model was used to predict puerperal endometritis controlled for rupture of membranes duration, low-grade fever (compared with normal body temperature), positive group B streptococcus status, mechanical cervical ripening, cervical ripening by prostaglandins, artificial rupture of membranes, meconium staining, epidural analgesia, and cesarean delivery. A multivariate logistic regression model was used to predict neonatal intensive care unit admission controlled for rupture of membranes duration, low-grade fever, positive group B streptococcus status, mechanical cervical ripening, artificial rupture of membranes, meconium staining, cesarean delivery, and neonatal weight of <2500 g. Results: This study included 687 women with rupture of membranes 12 to 18 hours and 1109 with rupture of membranes ≥18 hours. In both latency groups, the rates were higher for cesarean delivery, endometritis, surgical site infections, umbilical cord pH<7.2, neonatal intensive care unit admission, and sepsis workup among those with low-grade fever than among those with normal body temperature. Among women with low-grade fever, the positive likelihood ratios were 12.7 (95% confidence interval, 9.6–16.8) for puerperal endometritis and 3.2 (95% confidence interval, 2.0–5.3) for neonatal intensive care unit admission. Among women with rupture of membranes ≥18 hours, the rates were higher of Enterobacteriaceae isolates in chorioamniotic membrane cultures for those with low-grade fever than for those with normal intrapartum temperature (22.0% vs 11.0%, respectively; P=.006). Low-grade fever (odds ratio, 9.0; 95% confidence interval, 3.7–21.9; P<.001), artificial rupture of membranes (odds ratio, 4.2; 95% confidence interval, 1.5–11.7; P=.007), and cesarean delivery (odds ratio, 5.4; 95% confidence interval, 2.2–13.4; P<.001) were independently associated with puerperal endometritis. Low-grade fever (odds ratio, 3.2; 95% confidence interval, 1.7–6.0; P<.001) and cesarean delivery (odds ratio, 1.9; 95% confidence interval, 1.1–13.1; P=.023) were independently associated with neonatal intensive care unit admission. Conclusion: In women with rupture of membranes ≥12 hours at term, higher maternal and neonatal morbidities were reported among those with low-grade fever than among those with normal body temperature. Low-grade fever was associated with a higher risk of Enterobacteriaceae isolates in chorioamniotic membrane cultures. Moreover, low-grade fever may be the initial presentation of peripartum infection.