Early Effect of Epidural Analgesia on Fetal Acid-base Balance in the First Stage of Labour

Abstract

Introduction: Epidural analgesia is a consolidated therapeutic technique generally used for the relief of labor pain. Since its introduction in obstetrics, there have been many studies that evaluate the effect that this type of analgesia has over the course of labor, and its possible repercussions on the mother and the fetus/newborn by analyzing data at birth. However, there exist very few studies that analyze the early effect that epidural analgesia has on the fetus. Objectives: The main objective of this study is to analyze the early effects of epidural analgesia on the fetal status by evaluating the possible changes in the acid-base fetal state, the most precise way to evaluate fetal wellbeing during labor, and cardiotocographic (CTG) tracing of the fetal heart rate after the administration of an epidural. Methods: This is a prospective study of 193 patients, in which a determination of the fetal acid-base equilibrium was done before the administration of epidural analgesia and repeated 60 min afterwards, evaluating possible changes in the results motivated by analgesia. Results: There was a statistically significant descent on fetal blood pH after the administration of epidural analgesia, as well as a significant increase in the number of fetal heart traces with alterations. The descent of fetal pH was greater in patients that had some gestational associated conditions. Conclusion: The administration of epidural analgesia during the first stage of labor caused, as an early effect, a significant descent in fetal blood pH, without that descent being clinically relevant over the fetal status in healthy fetuses. There must be a strict control in fetuses with some initial alteration in the CTG tracings.