Fig 2 Expected numbers of women allocated to low and high risk groups for pre-eclampsia from cohort of 1000 women based on testing sequentially with model 1 at booking followed by model 2 at subsequent visits with threshold of 0.0047 at each gestational age up to 31 weeks. After initial screen, only high risk group are included in subsequent screening tests. To obtain these numbers we determined average threshold giving 99% sensitivity at each stage in ALSPAC (including high risk group only after initial screen) and applied this threshold in SWS. Model 1 includes maternal covariates and mean arterial pressure at first visit; model 2 additionally includes mean arterial pressure at gestational age of testing