This study aimed to determine the performance of screening for preeclampsia (PE) by maternal medical history and mean arterial pressure (MAP) at 11(+0) to 13(+6) weeks. In 5590 women with singleton pregnancies attending for routine care at 11(+0) to 13(+6) week's gestation we recorded maternal variables and measured the MAP. We excluded 397 because they had missing outcome data or the pregnancies resulted in miscarriage or termination. In 104 patients there was subsequent development of PE, 97 developed gestational hypertension, 574 delivered small-for-gestational-age newborns, and 4418 were unaffected by PE, gestational hypertension, or small for gestational age. A multivariate Gaussian model was fitted to the distribution of log multiple of the median MAP in the PE and unaffected groups. Likelihood ratios for log multiple of the median MAP were computed and used together with maternal variables to produce patient-specific risks for each case. Detection rates and false-positive rates were calculated by taking the proportions with risks above a given risk threshold. In the unaffected group, log MAP was influenced by maternal age, ethnic origin, smoking, family and personal history of PE, and fetal crown-rump length. In the prediction of PE, significant contributions were provided by log multiple of the median MAP, ethnic origin, body mass index, and personal history of PE. The detection rate of PE by log multiple of the median MAP and maternal variables was 62.5% for a false-positive rate of 10%. Maternal variables, together with MAP, at 11(+0) to 13(+6) weeks identify a group at high risk for development of PE.