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Epidural anesthesia can elevate a woman's temperature, but what effect does it have on maternal health or pregnancy outcomes?
Most women experience significant pain during their first labor, which is why obstetricians spend a considerable amount of time counseling women about their pain control options. Epidural analgesia is attractive to both patients and clinicians because it is the most effective pain control method available, is relatively safe, and has only moderate effects on the course of labor.1 Most first-time mothers choose epidural analgesia, even 57% of those who originally planned natural childbirth.2 Despite its popularity and safety, epidural analgesia is not without side effects, the most common of which is maternal fever. The link between epidural analgesia and a progressive increase in maternal temperature was first described in 1989.3 Since then, an increased risk of intrapartum fever in women receiving epidural analgesia has been confirmed in both randomized4-7 and observational studies.8-12 My purpose here is to outline the latest understanding of the frequency, proposed mechanism, and potential consequences of epidural fever.
Is my patient at risk for epidural fever?
The primary clinical risk factor for developing a fever after epidural analgesia is duration of exposure to the epidural itself.10,12,13 As a result, the risk of epidural fever is largely confined to nulliparous patients. Most multiparous patients deliver shortly after receiving epidural analgesia and, as a result, do not have a significantly increased risk of fever. In fact, randomized trials have shown only 4% of multiparas on epidural analgesia develop fever, versus 3% in controls.7 While a small subset of multiparous patients with prolonged labor may be at risk for epidural fever, they are difficult to identify prospectively for counseling.
What's the risk of epidural fever in nulliparous patients?
Accurately counseling an individual patient on her risk is complicated by wide variations in the risk of fever in different populations. In observational studies in which nulliparas were allowed to choose their method of analgesia, the risk of fever increased 10 to 14-fold with epidural analgesia. Randomized studies suggest that the independent contribution of epidural analgesia to intrapartum fever risk is four- to fivefold (Table 1). Ultimately, rates of intrapartum fever with epidural analgesia in nulliparas range from 13% to 33%. Rates at the upper end of this range have been observed in large public hospitals with primarily Hispanic populations. Conversely, rates at the lower end of the spectrum have largely been observed at private hospitals with predominantly Caucasian populations. Based on conservative calculations, epidural analgesia is theoretically associated with more than 400,000 additional cases of intrapartum fevers in the US every year. The rate of fever in a low-risk nulliparous population varies by patient population and by duration of epidural analgesia (Table 2): between 5% and 9% at 4 hours, 8% to 18% at 6 hours, and 11% to 24% at 8 hours.12,16