Maternal serum sFlt1 by clinical onset of preeclampsia matched to control samples in women with pre-existing diabetes (A), chronic hypertension (B), multifetal gestation (C), and previous preeclampsia (D). Open boxes are controls and shaded boxes are subjects who developed preeclampsia. The number above each box indicates the number of samples. The filled black circles are the median, the open circles are the 90th and 10th percentiles, and the top and bottom lines of the box are the 75th and 25th percentiles of the data for each group. Statistical significance is indicated by p values.