Introduction

Labor onset can be spontaneous or induced with regular or rhythmic uterine contractions. Prolonged labor, especially latent phase, has been associated with increased risk of caesarian deliveries, need for intrapartum interventions, adverse fetal outcomes such as poor APGAR scores at 5 minutes, and admission to newborn intensive care units (NICU) [2,3]. There are some inconsistencies in defining the active phase of labor. In 1978, Friedman observed that active labor started when there is a significantly increased rate of change in cervical dilation [4]. In the 2003 American College of Obstetrics and Gynecologists (ACOG) practice bulletin on approaches to limit intervention during labor and birth, it has been noted that most clinicians defined the active phase of labor at 3 or 4 cm cervical dilation [5]. Also, the 1998 World Health Organization partograph defined the beginning of an active phase of labor at 3 cm with a cervical dilation rate of at least 1 cm per hour [6]. However, recent evidence suggests that defining active labor at cervical dilatation of 5 or 6 centimeters may have similar obstetric outcomes as cervical dilatation happens substantially slower than originally reported by Friedman in his 1978 published book [7]. Zhang et al. in 2002 reported a substantially slower rate of dilation from 4-10 cm (5.5 hours) compared to what was reported by Friedman (2.5 hours) in 1978, with the 3-4 cm diagnostic criteria for active labor found to be too stringent for nulliparous parturients [8]. A follow-up study by Zhang et al. (2010) and Laughon et al. (2014) also reported substantially lower rates of dilation (0.5-0.7 cm per hour) compared to Friedman’s (1 cm per hour) [8,9], supporting earlier findings that the 3-4 cm diagnostic criteria for active labor might be too stringent. Guided by this new evidence, ACOG released a new diagnostic criterion for the active phase of labor in an obstetric care consensus statement in 2014, which advocated for adopting 6 cm cervical dilation as the threshold for the onset of the active phase of labor for most women [10] and late r on supported by the World Health Organization (WHO) in 2018 [11]. However, the feasibility and obstetric outcomes of defining the active phase of labor at cervical dilation of 6 compared to 4 centimeters in low-resource settings have not been evaluated. This study sought to compare the obstetrics outcomes of parturients whose active stage of labor was defined at a cervical dilation of 4 cm compared to 6 cm in Kenya.