Epidurals Can Increase Risk of Fever

Researchers from different institutions associated with Harvard University studied how fever resulting from epidural impacts a pregnancy and delivery
Randomized trials and observational studies show that maternal fever occurs in approximately 15%–20% of laboring women after epidural analgesia.  The cause of this fever is unclear.

One theory is that fever is due to infection because women who choose epidural have longer labors with multiple interventions, increasing the risk for chorioamnionitis.  Another theory is that epidural analgesia changes thermoregulatory mechanisms. Maternal heat is not dissipated when hyperventilation is inhibited and sweating is prevented by sympathetic blockade.  Another theory is that fever is attributable to a noninfectious inflammatory process initiated or enhanced by labor epidural analgesia. Some studies have demonstrated elevated interleukin (IL)-6 levels associated with this fever, and other studies have utilized placental histology as indirect evidence of a noninfectious etiology.

"Studies hypothesizing an association between neonatal encephalopathy or seizures and intrapartum maternal fever have assumed the fever resulted from infection such as chorioamnionitis. However, data suggest that among women delivering at term, most fever is related to epidural use rather than infection," they said.

What they found
They found that moms whose temperature spiked more than 101 degrees F while receiving an epidural were more likely to have a baby who is weak, needs assistance breathing and has early-onset seizures.

The findings suggest that epidural analgesia without accompanying maternal fever does not have an immediate effect on neonatal status, but that epidural analgesia with fever could have an impact on the fetus.

In past studies, experts have noted that a woman’s temperature may rise after she’s been given an epidural during labor. The study authors say that the higher a woman’s temperature rises after given epidural, the greater the risk is to the baby.  A trend was seen between the maximum maternal temperature and a significant increase in the incidence of hypotonia, assisted ventilation, 1- and 5-minute Apgar scores less than 7, and early-onset seizures in those with temperature elevation who received an epidural, the investigators said

"Maternal fever exceeding 101 F was associated with a twofold increase in the risk of transitional hypotonia, a threefold increased risk of hypotonia lasting greater than 15 minutes, and a twofold increased risk for assisted ventilation. ... Infants of mothers with fever greater than 101° F were also 6.5 times more likely to have a seizure compared with infants of mothers with a maximum temperature less than or equal to 99.5 ° F," they said.

Dr. Elizabeth A. Greenwell
Dr. Elizabeth A. Greenwell, previously from the Harvard School of Public Health and currently a postdoctoral fellow at the University of Colorado Denver School of Public Health, and colleagues tracked 3,209 first-time moms giving birth at Boston's Brigham and Women’s Hospital in 2000. All of the women were at low risk for delivery problems.

The researchers report that the babies of these women were two to six times more likely to be ill.
However, there was no risk to babies if the mom’s fever was at or below 99.5 degrees F.

The team believes that high body temperature in the mother can hurt the baby because a baby’s core temperature in the womb runs at least 1 degree F above the mother’s. That means a feverish mom equals a feverish baby.

In the study, 87% of the women took epidural during labor. Of these women, 19% had a fever greater than 100.4%. Meanwhile, only 2.4% of non-epidural-receiving women developed a fever that high. Overall, 45% of the women who received an epidural had a body temperature of at least 99.5%, compared to 13.2% for women without an epidural.


Just eight of the babies developed early-onset seizures. But four of these babies were born to moms who had a temperature higher than 100.4 degrees F during delivery, which suggests a link between a higher maternal body temperature and early-onset seizures, according to the researchers.

This observational study was partially funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and published in the journal Pediatrics.

So what now?
Researchers still aren't sure what the connection is between epidurals and maternal fever.  They do know that when fevers rise above 101 F after receiving epidurals the fetus suffers.  As the mother's core rises so does the fetus'.  Muscle weakness, low Apgar Scores and seizures are all possible. 

More research is needed and no changes in epidural use have been recommended.  Knowing that there could be a risk if fever accompanies the epidural may be enough to dissuade some mother's from the aid of an epidural, but it remains a mother's choice as to whether or not to use an epidural during labor and delivery. 

Sources

Pediatrics 2012;129:e447-54

http://www.ncbi.nlm.nih.gov/pubmed/20861420

http://www.ncbi.nlm.nih.gov/pubmed/11012136