July 27, 2012 — Contrary to previous studies, there’s no significant relationship between epidural anesthesia and an increase in maternal body temperature during labor, according to a new study published in the August issue of Anesthesiology.
In contrast, the study, by Michael A. Frölich, MD, from the Department of Anesthesiology at the University of Alabama at Birmingham, and colleagues, did find significant associations between temperature increase during induced labor and both higher body mass index (P = .0067) and longer time from rupture of membranes to delivery (P = .0077).
Reports over recent years suggest that possible causes of noninfectious maternal temperature elevations during labor include epidural analgesia, endogenous heat production by uterine contractions, and overheated delivery rooms. The authors sought to evaluate the first possible cause by conducting a prospective cohort trial.
Of 90 women with induced labor who were enrolled in the study, 1 was excluded because of a clinical diagnosis of chorioamnionitis, and 4 were excluded because they received acetaminophen for intrapartum pain. An additional 4 participants were excluded because of the availability of less than 4 hours of data. A total of 81 women undergoing induced labor were therefore included in the analysis.
Labor lasted an average of 11 hours and 41 minutes. All but 3 of the women received epidural analgesia. The median duration of epidural analgesia was 7.9 hours (interquartile range, 4.3 - 12.1 hours).
The authors found that temperature increased with length of labor. They calculated a very small average temperature trend, with an increase of 0.017°C/hour (P = .0093) over the course of 10 hours of labor. The population slope was calculated using the linear mixed model, β1.
Fever in laboring women was not associated with epidural analgesia. The authors did note, however, the absence of a temperature drop in the first 4 hours after initiation of epidural anesthesia.
The authors found a significant association between the time of rupture of membranes to delivery and body mass index (P = .0475).
Previous studies have reported maternal temperature elevations in women who received epidural analgesia in association with placental inflammation, neonatal sepsis work-up, pregnancy-induced hypertension, labor progress, and mode of delivery.
Numerous theories have been proposed as to why the temperature increases occur during so many different labor circumstances. In a press release, Dr. Frölich stated, "Long labor sustains an inflammatory process that may result in a temperature elevation. Also, the same mechanism may be responsible for patients who are overweight, since the link between obesity and inflammation is well established."
The authors propose that future research focus on better understanding the exact causes of noninfectious maternal intrapartum fever to help identify and treat women who are more prone to fever during labor.
The authors have disclosed no relevant financial relationships.
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