First stage progression in women with spontaneous onset of labor: A large population-based cohort study

Abstract

Objective: To describe the duration, progression and patterns of first stage of labor among Swedish women.

Design: Population-based cohort study.

Population: Data from Stockholm-Gotland Obstetric Cohort 2008-2014 including ¼ of all births in Sweden, the final sample involved a total of 85,408 women with term, singleton, vertex, live fetuses experiencing spontaneous labor onset and vaginal delivery with normal neonatal outcomes.

Main outcome measures: Time to progress during first stage of labor using three approaches: 1) Traverse time in hours to progress centimeter to centimeter, 5th, 50th (and 95th percentile); 2) Dilation curves for different percentiles, and; 3) Cumulative duration for the 95th percentile by parity and dilation at admission.

Results: Variation in both the total duration and the trajectory of cervical change over time is large. Similar to the general held view, the rate of cervical dilation accelerates at 5-6 centimeters. Among nulliparous women, the median time found in our population was faster than their counterparts in studies conducted on American and African cohorts. Among nulliparous and multiparous women our data suggest that the median cervical change over time is faster than 1 cm per hour during the first stage of labor. However, traverse time of cervical change at and beyond the 95th percentile is longer than 1 cm per hour.

Conclusions: Labor progression varies widely and labors experiencing a prolonged first stage can still result in normal outcomes. The assumption of 1 cm per hour cervical dilation rate for the first stage of labor may not be universally meaningful. There are differences in progression for women during first stage of labor in different populations. For prolonged labor progression to be more clinically meaningful, the association with adverse birth outcomes needs to be further investigated in specific populations.

Fig 1. Diagram of patient selection for study cohort.

Gestational age was determined using the following hierarchy: (a) embryo transfer, (b) first trimester ultrasound (c) early second trimester ultrasound offered to all women, (d) date of last menstrual period and (e) postnatal assessment. Characteristics of the study populations are reported as frequencies and percentages for categorical variables and as means and standard deviations or as medians and 10^th, 90^th percentiles for continuous variables, as indicated (Table 1).

Fig 2. Labor curve for a random sample of numerous women based on percentiles 5-95^th for nulliparous.

Labor curves with a reversed approach from fully dilated cervix in singleton term pregnancies with spontaneous onset of labor and vertex presentation, vaginal delivery and healthy neonates.

Fig 3. Labor curve for a random sample of numerous women based on percentiles 5-95^th for parity = 1.

Labor curves with a reversed approach from fully dilated cervix in singleton term pregnancies with spontaneous onset of labor and vertex presentation, vaginal delivery and healthy neonates.

Fig 4. Labor curve for a random sample of numerous women based on percentiles 5-95^th for parity = 2+.

Labor curves with a reversed approach from fully dilated cervix in singleton term pregnancies with spontaneous onset of labor and vertex presentation, vaginal delivery and healthy neonates.

Fig 5. The 95^th percentiles of cumulative duration among nulliparous.

Illustrate the 95^th percentiles of cumulative labor duration in parity = 0 and plotted as staircase lines based on the cervical dilation observed at admission, and centimeter by centimeter until full cervical dilation. The staircase cumulative duration is equal to the 95^th percentiles in Table 3.

Fig 6. The 95^th percentiles of cumulative duration among parity = 1.

Illustrate the 95^th percentiles of cumulative labor duration in parity = 1 and plotted as staircase lines based on the cervical dilation observed at admission, and centimeter by centimeter until full cervical dilation. The staircase cumulative duration is equal to the 95^th percentiles in Table 3.

Fig 7. The 95^th percentiles of cumulative duration among parity = 2.

Illustrate the 95^th percentiles of cumulative labor duration in parity = 2+ and plotted as staircase lines based on the cervical dilation observed at admission, and centimeter by centimeter until full cervical dilation. The staircase cumulative duration is equal to the 95^th percentiles in Table 3.