A critical step for the development of a mathematical model
able to generate a reference CS rate is the population that
will serve as the basis for establishing the relationship
between maternal characteristics and the probability of caesarean section. Due to the global nature of our endeavour,
we assumed we would need a multi-country population
with relatively low CS rates and, at the same time, good outcomes of labour and childbirth. We used the WHO MultiCountry Survey on Maternal and Newborn Health (WHO
MCS) to create our reference population. Detailed description of this study has been published elsewhere.21 Briefly,
the WHO MCS was a cross-sectional study implemented in
359 health facilities in 29 countries. Countries, provinces (or
other equivalent political divisions within countries), and
health facilities were randomly selected to participate in the
WHO MCS through a stratified, multistage cluster sampling
strategy. Health facilities were only eligible if they dealt with