The aim of this study is to determine the influence of oxytocin on fetal well-being during labor in patients receiving epidural analgesia (ELA) with the use of cardiotocography (CTG) and doppler ultrasonography.

CTG is a commonly used technique to monitor the fetal heartbeat and contractions of uterus during pregnancy and labor. The maternal-fetal doppler ultrasonography is a non-invasive method used for the pregnancy surveillance.

Various psychological and psychosocial factors impact the perception of labor pain. Its intensity is described differently by each patient - some claim it to be the worst pain that they experienced during their lives. Usually, the labor pain is more severely experienced by the patients giving birth for the first time and those with induced labor.

Nowadays, there are many non-pharmacological (e.g. acupuncture, massage, TENS) and pharmacological (anesthetic gas, opioids, ELA) methods of labor pain management. ELA is a regional anesthesia, in which the anesthetic drug is injected into the epidural space with the aim to block the pain experienced by the patient without impacting patients ability to move or push during labor. The safety of the procedure is well-discussed and documented in Cochrane review from 2018, which shows no adverse impact on the proportions of Caesarean section, long-term backache, or neonatal outcomes. It is considered to be a golden standard for labor pain management.

Oxytocin is a well-known hormone used for the induction of labor and to stimulate the uterine contraction during labor. The impact of oxytocin alone on CTG pattern and maternal-fetal doppler ultrasonography is discussed in the literature. However, the cumulative effect of ELA and oxytocin remains unclear. Some researchers claim that ELA increases the frequency of uterine contractions and that the additional use of oxytocin leads to higher risk of uterine hyper-stimulation and unreassuring CTG patterns. Whereas the others state that ELA weakens the strength of uterine contractions leading to slow progression of labor and the need to use or increase the use of oxytocin.

There are no data on how the cumulative use of oxytocin and ELA impacts the maternal-fetal flows during labor.

This is a randomized controlled trial performed at the Clinical Department of Obstetrics and Perinatology at the National Medical Institute of the Ministry of the Interior and Administration. The study will recruit 200 patients in either labor induced by oxytocin or stimulated with oxytocin at 37-42 weeks of gestation, requesting the epidural labor analgesia (ELA) and meeting the inclusion criteria. The patients will be individually randomized to either the study group (n=100), in which the use of oxytocin will be continued after the administration of ELA; or to the control group (n=100), in which the oxytocin will be changed to 0.9% sodium chloride solution after the ELA administration.

The vital signs (blood pressure, saturation, heart rate) and the Doppler velocities in the uterine arteries, umbilical artery and the fetal middle cerebral artery will be measured directly before the administration of ELA and then after 30, 60 and 120 minutes. After 2 hours the patients will be examined to assess the progress of labor. If no progress is detected due to the secondary weakening of uterus contractile function, the oxytocin will be reintroduced in the control group.

Additionally, the velocities in the uterine arteries will be measured during the first day after the delivery.

The labor and neonatal outcomes (e.g mode of the delivery, duration of labor, Apgar score, umbilical artery blood gas analysis) will also be recorded.

Inclusion Criteria:

• ≥ 18 years old
• singleton pregnancy
• labor induced by oxytocin or stimulated with oxytocin
• signed informed consent form
• cervical dilation ≥ 3cm
• patient requesting and eligible for epidural analgesia
• normal CTG trace for at least 30 minutes before epidural analgesia

Exclusion Criteria:

• less than 18 years old
• preterm delivery
• multiple pregnancy
• fetal malformations
• less than 3cm cervical dilation
• lack of CTG trace for at least 30 minutes before epidural analgesia
• patient not requesting or not eligible for epidural analgesia
• informed consent form not signed
• spontaneous labor without the use of oxytocin

Data will be available on reasonable request

Study protocol will be available following its publication. The anonymized participant data will become available upon publishing the protocol and the results of the study.

The data will be provided on reasonable request. (contact details: joanna.krol@wum.edu.pl).