It has been confirmed in various studies and is widely accepted that epidural analgesia increases the rate of intrapartum fever. Nevertheless, there remains a considerable controversy regarding whether EA-related intrapartum fever causes adverse maternal and neonatal outcomes. A study showed that the rate of EA-related intrapartum fever could be as high as 46%; and 25.2% and 22.5% of the women with intrapartum fever required caesarean delivery and assisted delivery, respectively, all of which were higher than those in women without intrapartum fever. We found that 8.3% of the mothers were converted to caesarean delivery, a rate that was significantly lower than those of other reports. However, the rate of forceps delivery in our study was 49.0%. We believe that the reasons for the discrepancies include: (1) a high EA-related intrapartum fever rate (39.4%) and long durations of first and second stages of labour; it was impossible to differentiate EA-related intrapartum fever from intrauterine infection-related fever; therefore, forceps delivery was used in those deliveries with intrapartum fever eligible for assisted vaginal delivery, so as to prevent adverse neonatal outcomes (such as cerebral palsy) because of intrauterine infection; (2) a high incidence of category II and III foetal heart rate tracing (69.6% in the fever group); to reduce the incidence of neonatal asphyxia, obstetricians were more inclined to use assisted delivery to shorten the duration of the second stage; (3) a high rate of amniotic fluid contamination (36.7%); intrapartum amniotic fluid contamination increases the incidence of foetal distress and therefore leads to adverse neonatal outcomes; for these reasons, steps should be taken promptly to accelerate the delivery for the nulliparous women presenting with amniotic fluid contamination; (4) a low conversion rate to caesarean delivery resulting in a high assisted delivery rate. EA-related intrapartum fever significantly increases the rate of assisted delivery; nevertheless, it will not increase the rate of caesarean delivery.
There have been various views regarding the impact of EA-related intrapartum fever on neonatal outcomes. Some studies suggested that it is associated with neonatal asphyxia, requiring more assisted ventilation, oxygen usage, and resuscitation procedures, as well as increased incidence of neonatal sepsis and usage of antibiotics. It is also possibly related to early neonatal seizures[6,12]. However, there are also studies suggesting that EA-related intrapartum fever is only a rise of body temperature of a benign nature, and there is no causal relationship between intrapartum fever and neonatal nervous system outcomes. We showed that, despite the fact that the neonatal asphyxia rates in both groups were not high, the rates of neonatal asphyxia, hospitalisation, and acidosis in the fever group were higher than those of the non-fever group, suggesting that EA-related intrapartum fever increases the rate of adverse short-term neonatal outcomes. At present, the short-term impact of EA-related intrapartum fever on neonates requires more research.
The mechanism of EA-related intrapartum fever remains unclear, and there is no effective method for controlling EA-related intrapartum fever. Nevertheless, minimising the incidence of EA-related intrapartum fever and shortening the duration of fever may be the effective ways to reduce maternal and neonatal adverse outcomes. We believe that two aspects deserve attention. Firstly, we must optimise the dosing regimens of epidural analgesia (e.g., various types, concentrations, and administration routes of local anaesthetics). Some studies confirmed that different ways of drug administration affect the rates of EA-related intrapartum fever. Delivering intermittent low-dose ropivacaine can reduce the rates of intrapartum fever and assisted delivery. The American Association of Anaesthesiologists recommends the use of low-dose local anaesthetics and patient-controlled epidural analgesia to reduce maternal and neonatal side effects. In this study, patient-controlled epidural analgesia of low-concentration ropivacaine was used for all nulliparous women; however, 39.4% of the patients still had intrapartum fever. For these reasons, optimising the dosing regimens of epidural analgesia should be a direction of further studies. Secondly, shortening the duration of labour and reducing the incidence and duration of intrapartum fever are effective strategies to reduce the adverse maternal and neonatal outcomes. Prolonged labour is an independent risk factor for intrapartum fever; therefore, avoiding prolonged labour can effectively control intrapartum fever. The reason why multiparous women are less likely to have intrapartum fever is that they have rapid labour. Measures for shortening the labour duration include: (1) reasonable and timely switching of the delivery mode; when abnormal foetal heart rate tracing results or protracted labour occur, reasonable conversion to caesarean delivery in the first stage of labour and timely use of assisted delivery in the second stage can effectively reduce the duration of labour; in our study, all seven cases of severe neonatal asphyxia and 67% of mild neonatal asphyxia events occurred during vaginal births, suggesting that timely conversion to caesarean delivery in cases of intrapartum fever may reduce the neonatal asphyxia rate; (2) using a higher dose of oxytocin as early as possible in the first stage of labour, and maintaining the usage in the second stage; even low concentrations of local anaesthetics can inhibit tocolysis, affecting coordinated contractions between the abdominal muscles and the pelvic floor muscle group, as well as weakening the mothers’ feelings of passive exertion; for these reasons, large doses of oxytocin need to be continuously used to provide effective contractions; (3) other measures such as minimising the usage of manual rupture of membranes, reducing the number of vaginal examinations, and use of temperature-lowering methods as soon as possible when body temperature rises.
Strengths and limitations
Our study was a single-centre study with a large sample size. The study focused on the population of nulliparous women who received low-dose local anaesthetics and patient-controlled epidural analgesia as recommended by the current guidelines. This population of nulliparous women may have prolonged labour stage associated with epidural analgesia that made them more susceptible to developing fever. Management of the delivery process and analgesia protocol are followed according to the uniform standards in our medical centre, which limits the influence of the outcomes by other different delivery management techniques. There are several limitations in this study. Firstly, it was a single-centre study, and therefore may be subject to selection bias. Secondly, it was a retrospective case control study, which would make confounding inevitable in the study. For these reasons, we instituted strict inclusion and exclusion criteria. Further research through multi-centre prospective studies are needed to validate our findings.