Progression of first stage of labor, in low risk nulliparas in South
Asian Population: A prospective observational study
Abstract
Objective: To compare labor pattern at 4cm and 6 cm cervical dilatation
in spontaneous labor in low risk nulliparous women. Design: A
prospective observational study. Setting: The study was conducted in a
tertiary referral center of India. Population: Study involved 500 low
risk nulliparas; singleton term pregnancy; vertex presentation in
spontaneous labor; cervical dilatation ≤4cm and no contraindications for
vaginal delivery. Methods: Women were randomized into two groups A and B
of 250 each, active phase considered at 4cm for group A and 6cm for
group B. Labor duration was calculated and average labor curves were
drawn. Main Outcome: To study the average labor pattern curve. Results:
Mean duration of active phase from 4- 10 cm is 5.12±2.01 hours and from
6-10 cm is 2.79 ± 1.72 hours. 95th percentile values suggest that it
took 5-6hours in progression from 4-6 cm and again 5-6 hours from
6-10cm. The minimum labor progression rate can be as low as 0.5cm/hour,
still vaginal delivery can be achieved. The slope of labor curve steeps
after 6cm, suggesting 6cm as the onset of active phase. Conclusion:
Allowing labor to continue for a longer period before 6 cm of cervical
dilation may reduce the rate of unnecessary intrapartum intervention and
caesarean section for labor dystocia. Large-scale studies further needed
for standardization of cutoff values for differentiating normal from
abnormal labor. Funding: We received no financial support for the
research, authorship, and/or publication of this article. Keywords:
labor duration, nulliparous women, labor pattern, active phase of labor