Sample SizeThe power calculations f

Sample Size
The power calculations for this study were based on the
assumption of detecting a 40% reduction in the incidence of GDM
(GDM incidence 40% in the usual care municipalities and 24% in
the intervention municipalities). With these incidences of GDM,
the power of the study would be 0.80, significance level 0.05, and
coefficient of variation of rate between clusters, indicating cluster
sampling, 0.1. On the basis of these assumptions, 420 women were
needed for the analyses. As we expected a drop-out rate similar to
the one in our pilot study (25%), we needed to recruit a total of
560 women to the study.