Intrapartum pyrexia is said to occur when maternal temperature is > 38 °C on one reading or > 37.5 °C on two consecutive readings taken at least 1-2 hours apart. Pyrexia in labour may be a marker of infection requiring investigation and antibiotic therapy. However, there are many other medical causes of pyrexia (e.g. inflammatory disease, thyrotoxicosis, pulmonary embolism, malignancy) that should not be forgotten. In addition, epidural analgesia itself may be associated with a gradual increase in maternal (and thus fetal) temperature after about 6-8 hours, of up to 0.5-1 °C, in about 20% of parturients. Most studies, however, are poorly controlled and the phenomenon is controversial (for example, women with predisposing factors for infection are often those who request epidural analgesia).
Suggested mechanisms include alteration of afferent temperature-related neural input to the hypothalamus, impaired thermoregulatory mechanisms in the lower body (such as absent shivering in the legs) and a re-setting of the central ‘thermostat’.
The fetal temperature is ~1 °C higher than the maternal core, and follows maternal oral readings more closely than tympanic.
Fetal heart rate may increase as a direct consequence of maternal pyrexia.
Problems and special considerations
The mechanism behind epidural-related fever in labouring women remains controversial; it is thought to be the consequence of a sterile inflammatory reaction. The presence of maternal pyrexia may trigger additional investigations in the mother or neonate or interventions to expedite delivery. It is therefore important that all anaesthetists, obstetricians, midwives and paediatricians are aware that the phenomenon may exist. In protocols and guidelines for the management of pyrexia during labour, provision should be made for the effect of epidurals; separate instructions may be required for mothers with epidurals and those without.
Pyrexia itself has been implicated in causing premature labour and may stress an at-risk fetus. Neonatal encephalopathy is more common if mothers are pyrexial during labour, although whether this is related to the increased temperature itself or to any underlying cause (particularly infection) is uncertain.
Infection causing pyrexia is a potentially serious problem, since severe sepsis may affect both the mother and the fetus. Thus, most protocols call for screening tests and possibly antibiotic therapy if infection is suspected.
Management options
In most cases, mild pyrexia is not in itself troublesome. Fanning, sponging or treatment with paracetamol may be used, although the possibility of masking underlying sepsis should not be forgotten. Pyrexia above 38.5 °C, especially if it occurs within 6 hours of siting the epidural, is unlikely to be related to epidural analgesia. If infection is suspected, screening should include blood cultures, high vaginal swabs and mid-stream urine sampling. Infection may not be accompanied by localising signs, at least initially; in addition, white cell count may increase during normal labour to as high as 30 x 109/l (especially if steroids have been given for prematurity).
Mothers who are pyrexial and who request epidural analgesia present a separate dilemma. Local guidelines should be followed, but evidence of infection at the site of injection or sepsis are relative contraindications to neuraxial techniques, since regional blockade may be complicated by localised infection or cardiovascular compromise. For mild localised infection, such as chorioamnionitis (which may be associated with subclinical bacteraemia), regional analgesia is generally felt to be safe if covered with antibiotic therapy.
Set procedures should exist for monitoring of maternal temperature and management of pyrexia, including provision of regional blockade in pyrexial mothers and neonatal screening. A high level of general awareness and education is important, since staff of all disciplines may be unaware of the relationship between epidural analgesia and pyrexia.
Key points
• There are many causes of fever, the most common of which is infection.
• Epidural analgesia exceeding 6-8 hours has been associated with pyrexia.
• Protocols should exist for monitoring of temperature during labour and screening ± treatment of pyrexial mothers.
• Maternal pyrexia does not always contraindicate regional techniques.
Further reading
Riley LE, Celi AC, Onderdonk AB, et al. Association of epidural-related fever and noninfectious inflammation in term labor. Obstet Gynecol 2011; 117: 588-95.
Segal S. Labor epidural analgesia and maternal fever. Anesth Analg 2010; 111: 1467-75.
Sultan P, David AL, Fernando R, Ackland GL. Inflammation and epidural-related maternal fever: proposed mechanisms. Anesth Analg 2016; 122: 1546-53.