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.