In pregnancies at low risk for PE, the gestational-age distribution is
shifted to the right and, in most pregnancies, delivery will occur before the
development of PE. In pregnancies at high risk for PE, the distribution is
shifted to the left. The risk of PE occurring at or before a specified
gestational age is given by the area under the distribution curve. As an
illustration, in the low-risk group, the risk of PE at <34 weeks of
gestation is 0.01 or 1% and in the high-risk group, the risk is 0.6 or 60%.
Diagram adopted from Wright et al.144