Epidemiology

Objective

Friedman’s curve, despite acknowledged limitations, greatly influenced labor management. Interventions to hasten birth are now ubiquitous, challenging contemporary study of normal labor. Our purpose was to characterize “normal” active labor and second stage durations in a large, contemporary sample experiencing minimal intervention.

Study Design

Secondary analysis of national, validated MANA Stats data registry (n = 75,243), prospectively collected 2012-2018 to describe labor and birth in settings absent common obstetric interventions [oxytocin, cesarean].

Results

Compared to multiparous (G1+) women (n = 32,882), nulliparous (G0) women (n = 15,331) had significantly longer active labor [median 7.5 vs. 3.3 hours] and second stage [median 1.1 vs. 0.2 hours].

Conclusion

Contemporary US women with low-risk pregnancies who intended birth in settings absent medical intervention and in spontaneous labor with a live, vertex, term, singleton, non-anomalous fetus experienced labor durations that were often longer than prior characterizations. The median duration of G0 active labor was nearly twice as long and the 95th% more than three times longer than 1955 estimates [median 7.5 vs. 4.0 hours; 95th% 34.8 vs. 11.7 hours]. These durations were also longer than recent estimates [a 2018 systematic review estimated a range of 3.7 – 5.9 hours for G0 active phase]. The duration of G0 second stage was slightly longer at the median and more than twice as long at the 95th%, compared to 1955 estimates [median 1.1 vs. 0.8 hours; 95th% 5.5 vs. 2.5 hours]. Median G1+ active labor durations were 1.5 hours longer than 1956 estimates but 1.6 hours shorter at the 95th% [median 3.3 vs. 1.8 hours; 95th% 12.0 vs. 13.6 hours]. G1+ second stage durations were similar to prior estimates. Findings suggest that G0 active phase may be longer than previously understood when interventions to hasten birth are rare. Second stage duration estimates are consistent with prior research. Results overcome prior and current sampling limitations to refine understanding of normal labor durations.