A Higher Baseline Body Temperature May Be Key to Labor-Associated Fever


BANFF, ALTA. — Some women who develop fever during labor may have a predisposition to labor-associated fever and may be identifiable by their higher baseline body temperatures, Tiffany Gelfand, D.O., said at the annual meeting of the Society for Obstetric Anesthesia and Perinatology.

And among women predisposed to labor-associated fever, epidural analgesia may have an additive effect, suggested Dr. Gelfand of Brigham and Women's Hospital, Boston.

“Maternal fever is not a benign thing; it's been related to neonatal cognitive deficits and cerebral encephalopathy, and even cognitive deficits 6 years out,” she said in an interview. “We don't really know what the interaction is between the epidural and the patients who are predisposed to have a fever, but we really need to find those risk factors before we go ahead and say that certain patients shouldn't have an epidural.”

Her prospective study followed 107 women in labor, at term, with maternal temperature measured every hour from admittance until delivery. It found that among 86 women who received epidural, and 21 who received either opioids or no analgesia, 35% developed a temperature above 99.5° F, and 17% had a temperature above 100.4° F. Fever was much more common in women who received epidural, compared with those who did not (37% vs. 14%), she said. But a common characteristic of all women who became febrile was a higher baseline body temperature.

“What was so interesting about this study was that these patients were already different the second they walked through the door. Even before they had an epidural, their baseline temperature, although afebrile, was significantly different. We don't know why they are different, and we need to figure that out.”

The study shows that the gradual, steady rise in temperature that has been previously reported with epidural analgesia is actually an artifact, due to averaging patients who develop clinical fever and those who do not, explained Dr. Gelfand. When women who became febrile were removed from the analysis, the rest demonstrated consistently low temperatures throughout labor, she said. “We think it might be some of type of inflammatory cause—perhaps an undisclosed infectious source,” she speculated, and noted that the nature of the fever was also different in women who received epidural, compared with those who did not. “Among women undergoing natural childbirth, we saw fever that responded well to acetaminophen, whereas in women who received the epidural, their fever did not respond to acetaminophen. We think it might be a different mechanism.”

A further analysis of the study, presented as a poster, looked at only the 86 women who received analgesia and found that, compared with the afebrile women, women who became febrile had some known obstetric risk factors such as longer time from rupture of membranes and a higher number of vaginal exams.

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