Evaluation of customization assumptions
In order to evaluate the assumptions of normality and constant CV we examined the data as follows. The data were sorted by the mean estimated TOW based on the Gardosi model and divided into eight contiguous equal length intervals, where each interval represents cases with a specific value of TOW (the mean birth weight value in the interval). The number of observations in each interval were not equal with fewer observations for the extreme intervals. However, there were substantial observations in each for the mean, the standard deviation and the percentiles to be estimated accurately. For each interval, we computed the empirical percentiles of birthweight and the standard deviation as well as the mean predicted TOW from the Gardosi model. We also computed the percentiles using the normality and the constant CV assumption from the Gardosi model. The results are presented in Figs 