The better the labour epidural, the more often the fever

Design

Multicentre prospective observational study

Population

952 nulliparous women at term with epidural labour analgesia

Primary outcome

Intrapartum hyperthermia ≥38°C

Effect

13% febrile; OR 1.64 (95% CI 1.40–1.91) per point lower time-weighted pain

This multicentre prospective observational study followed 952 nulliparous women at term with a singleton cephalic baby who planned vaginal birth with epidural analgesia. Pain scores were recorded during contractions from before the block through to the end of the third stage, and summarised four ways.

Intrapartum hyperthermia (38°C or higher) occurred in 13%. After adjustment, lower pain on every measure was associated with higher odds of fever — for example, odds ratio 1.64 per point lower in time-weighted average pain (95% CI 1.40 to 1.91). Women whose time-weighted average pain was 3 or less had over eight times the odds of fever (OR 8.67, 4.19 to 17.9).

The finding fits the theory that a denser sympathetic block impairs sweating and heat loss, though an observational study cannot prove that. It is useful at the bedside: epidural-related fever is common and usually non-infectious, but it still triggers sepsis workups and neonatal evaluation. It is not a reason to provide less effective analgesia; the question for future trials is whether the block can be less dense without losing comfort.

• Expect intrapartum fever in about one in eight nulliparous women with labour epidurals.
• Monitor temperature regularly, particularly when the block is very dense or pain scores are near zero.
• Assess a febrile woman for infection as usual; epidural-related fever remains a diagnosis of exclusion.
• Do not reduce analgesia quality to prevent fever on this evidence.
• Tell the neonatal team about maternal fever, as it affects newborn assessment.

Why it matters

It links a common, costly labour-ward problem to block density rather than chance.

Don't overread it

This was observational; it shows an association between low pain and fever, not that a denser block causes it.

The statistics, in plain English

An odds ratio of 8.67 at the lowest pain level is large, but its interval (4.19 to 17.9) is wide, so the true size is uncertain. These inflection points were found within the same data, which tends to exaggerate them.

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