Methodology

Study design

This was a prospective cohort study that compared obstetrics outcomes of term parturients among whom active stage of labor was defined at a cervical dilation of 4 cm versus 6 cm at Kenyatta National Hospital, the largest teaching, and referral hospital in Kenya.

Power and sample size calculation

Power and sample size calculation was estimated according to Charan and Biswas (27) at an α of 1.96 at 95% confidence interval, statistical power of 80%, and an anticipated incidence of oxytocin administration of 36.6% at 6 cm and 58.5% at 4 cm. The incidence data were obtained from Kauffman et al., 2002 [12]. Assuming a recruitment ratio of 1:1, 162 participants (81 at 4 cm and 81 at 6 cm) were required. After adjustment by a factor of 10% to cover loss to follow up, 180 participants, 50% at 4 cm cervical dilation and 50% at 6 cm cervical dilation were required.

Study procedures

Eligible parturients were those in spontaneous labor at term (37-42 weeks) gestation and having a cervical dilation of either 4 or 6 cm, cephalic presentation, reassuring fetal heart rate. Parturients with a previous uterine scar, multiple gestations, and medical comorbidities such as cardiac disease in pregnancy, diabetes mellitus, chronic hypertension, and HIV/AIDS with unknown viral loads were excluded. On admission, the cervical dilatation was assessed by a skilled trained midwife by performing a sterile vaginal examination which was confirmed using the cervical dilation and effacement chart. Informed consent was obtained from those at 4 cm and 6 cm cervical dilatation respectively until the required sample size (180) was reached. Enrolled participants were then monitored up to 24 hours postpartum and outcome data obtained.

Data collection

Interviewer administered questionnaires were used to collect data on sociodemographic and reproductive characteristics. Additional data was obtained from parturient’s medical records. Outcome data such as number of vaginal examinations and intrapartum interventions including amniotomy and oxytocin administration, and mode of delivery were obtained from medical records. Records of adverse maternal outcomes including cervical tears, primary PPH, early onset of sepsis, and adverse neonatal outcomes such as low 5-minute APGAR scores, need for resuscitation and oxygen administration, neonatal sepsis, and NBU admissions were also obtained from maternal and newborn medical records.

Statistical analysis

Categorical data were summarized as proportions and compared using the Chi-square or Fisher’s exact test. Continuous data were summarized as means with standard deviations and compared using the t-test if distributed normally and Mann Whitney U test if skewed. The association between cervical dilatation at a definition of the onset of active labor and obstetric outcomes was evaluated by a test for fitness in relation to expected risks and the corresponding 95% confidence intervals. P-value < 0.05 was considered statistically significant. Data were analyzed using Statistical Package for Social Scientists Software version 25.