Spontaneous labor progression for vaginal births is slower than expected in many women

Cervical dilatation during labour for vaginal births can progress more slowly than the widely accepted benchmark of 1 cm/hour in many women, according to a new data published this week in PLOS Medicine by Olufemi Oladapo, Medical Officer at WHO Department of Reproductive Health and Research including the UNDP/UNFPA/UNICEF/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Switzerland, and colleagues.

As part of the World Health Organization's Better Outcomes in Labour Difficulty (BOLD) project, the authors examined the patterns of labour progression based on cervical dilatation over time in a cohort of 5,606 women in Nigeria and Uganda who gave birth vaginally, with no adverse birth outcomes, following onset of spontaneous labour. They found that median time to advance by 1 cm exceeded 1 hour until 5 cm was reached for women having their first child and women who had given birth previously. Furthermore, women giving birth to their first child and progressing at the slowest rates (95th percentile) may take up to 7 hours to progress from 4 to 5 cm, over 3 hours to progress from 5 to 6 cm, and up to 9 hours to progress from 6 to 10 cm.

The authors noted that as labour may not naturally accelerate in some women until a cervical dilatation of at least 5 cm, interventions to expedite labour before this dilatation is reached may be inappropriate, irrespective of whether or not the woman has given birth before.

The authors say: "Our labour progression data clearly demonstrate that a minimum cervical dilatation rate of 1 cm/hour throughout the period traditionally described as active phase may be unrealistically fast for some women and should therefore not be universally applied as a threshold for identifying abnormally progressing labour." They add that "Averaged labour curves may not truly reflect the variability associated with labour progression, and their use for decision-making in labour management should be de-emphasized."