Duration of spontaneous labour in 'low-risk' women with 'normal' perinatal outcomes: A systematic review

Background: Despite decades of research, the concept of normality in labour in terms of its progression and duration is not universal or standardized. However, in clinical practice, it is important to define the boundaries that distinguish what is normal from what is abnormal to enable women and care providers have a shared understanding of what to expect and when labour interventions are justified.

Objectives: To synthesise available evidence on the duration of latent and active first stage and the second stage of spontaneous labour in women at low risk of complications with 'normal' perinatal outcomes.

Search strategy: PubMed, EMBASE, CINAHL, POPLINE, Global Health Library, and reference lists of eligible studies.

Selection criteria: Observational studies and other study designs.

Data collection and analysis: Four authors extracted data on: maternal characteristics; labour interventions; duration of latent first stage, active first stage, and second stage of labour; and the definitions of onset of latent and active first stage, and second stage where reported. Heterogeneity in the included studies precluded meta-analysis and data were presented descriptively.

Main results: Thirty-seven studies reporting the duration of first and/or second stages of labour for 208,000 women met our inclusion criteria. Among nulliparous women, the median duration of active first stage (when the starting reference point was 4 cm) ranged from 3.7-5.9 h (95th percentiles: 14.5-16.7 h). With active phase starting from 5 cm, the median duration was from 3.8-4.3 h (95th percentiles: 11.3-12.7 h). The median duration of second stage ranged from 14 to 66 min (95th percentiles: 65-138 min) and from 6 to 12 min (95th percentiles: 58-76 min) in nulliparous and parous women, respectively. Sensitivity analyses excluding first and second stage interventions did not significantly impact on these findings CONCLUSIONS: The duration of spontaneous labour in women with good perinatal outcomes varies from one woman to another. Some women may experience labour for longer than previously thought, and still achieve a vaginal birth without adverse perinatal outcomes. Our findings question the rigid limits currently applied in clinical practice for the assessment of prolonged first or second stage that warrant obstetric intervention.