Maternal sFlt1 was significantly elevated 2 to 5 weeks before the onset of preeclampsia in the subjects with previous preeclampsia, as well as within 1 week of the clinical onset of preeclampsia (Figure 4D). However, sFlt1 concentrations were not significantly elevated before the onset of preeclampsia in any of the other high-risk groups (Figures 4A, B and C). Similarly, the concentration of maternal sEng was not significantly elevated in any of the high-risk groups immediately before or close to the onset of preeclampsia compared with samples from gestational age matched controls (Figures 5A, B, C and D). Of note, there was a modest but statistically significant elevation in sEng at ≥18 weeks before the onset of preeclampsia among the chronic hypertension patients compared with their matched controls. Lastly, the concentration of maternal PlGF was not significantly lower among any of the high-risk groups (Figures 6A, B, C and D) except at 6–9 weeks in the chronic hypertensive group (Figure 6B). In addition, the ratio of the angiogenic factors was not different in any of the high-risk groups before the onset of preeclampsia compared with samples from gestational age matched controls (data not shown).