Impact of low-dose epidural analgesia on labour progression in Robson Classification Group 1 parturients: a single-centre retrospective observational study

The influence of epidural analgesia (EA) on the course of labour is still a matter of concern in modern obstetrics. Despite numerous studies have analysed labour progression, their findings are often inconsistent with regard to the effect of labour analgesia. In fact, women with EA have often been excluded, or included as the main study population, or represented the outright concern of the study, lacking comparison with a control group. Moreover, women who delivered via caesarean delivery (CD) have been routinely dropped from this kind of analysis, therefore limiting the generalisability of the results. Our study was specifically designed to address this gap by focusing on a homogenous cohort of low-risk patients (Robson Classification Group I), who received or not low-dose EA for labour, and who had either a vaginal or a caesarean delivery, with the aim of analyzing data on cervical dilation and fetal head station patterns. This retrospective study was conducted at Policlinico A. Gemelli IRCCS, Rome, retrieving data between October 1st 2008 and October 31st 2018 from the electronic Labour Suite database. The study was approved by the territorial Ethics Committee (ID 6077, prot. 0027680/23) and registered on ClinicalTrials.gov (NCT06987591). Waiver of informed consent was applied, as only anonymised data were used. We selected 6030 Robson Classification Group 1 women, aged between 18 and 40 years, who presented with a neonatal weight between 2500 and 4000 g, a cervical dilatation < 7 cm at admission and a minimal duration of labour of 3 h. Patients were divided into four groups according to the mode of delivery (vaginal or caesarean) and the presence or absence of EA: VD-e and CD-e when EA was performed in women who delivered via vaginal route or caesarean delivery, respectively; VD-n and CD-n in women without EA who delivered via vaginal route or caesarean delivery, respectively. Our primary endpoint was to describe the rate of cervical dilatation and fetal head station. Secondary endpoints were length of active phase and second stage (in hours), type of vaginal delivery (eutocic or instrumental), rate of maternal complications and episiotomy in the VD groups, fetal indicators (Apgar score at 1 and 5 min after birth, admission in NICU (neonatal intensive care unit, NICU)). The primary endpoint was evaluated through the average cervical dilation and fetal head descent curves and the estimated transverse times of cervical dilation and fetal head descent. To this end, a high-degree mixed polynomial regression, and an interval censored regression were respectively used. Women receiving EA showed patterns of labour progression different from those of women without EA. However, we conducted descriptive research, which cannot support causal inference. The cervical dilation and fetal head station curves showed a similar progression over time, indicating that only minor differences existed. Overall, no differences were found in the progression from 1 cm integer to the next of cervical dilation and fetal head station between women who underwent or not EA, with some minor exceptions. EA seems to accelerate cervical dilation, but the active phase appeared significantly longer in the group who vaginally delivered (VD-e 3.4 ± 2.2 h vs VD-n 2.9 ± 2.2, p value < 0.001). Similarly, the second stage seemed significantly prolonged in women under EA, irrespective of the route of delivery (VD-e 1.3 ± 0.9 versus VD-n 1 ± 0.8 h, p value < 0.001; CD-e 0.9 ± 1.4 h versus CD-n 0.6 ± 1.2 h, p value = 0.01). Other maternal (including haemorrhages, perineal lacerations, episiotomy rate) and neonatal (1–5 Apgar, admission in NICU, death) outcomes were similar, except for instrumental vaginal delivery, almost twice as frequent in the EA group (VD-e 14.7% vs VD-n 8.4%, p < 0.001). Intermittent low-dose EA seems to only modestly affect labour progression, in the absence of associations with relevant health outcomes. ClinicalTrials.gov (NCT06987591)