Proposed clinical management of pregnancies after combined screening for pre-eclampsia at 19-24 weeks' gestation

Objective To estimate the patient-specific risk of pre-eclampsia (PE) at 19-24 weeks' gestation by a combination of maternal characteristics and medical history with multiples of the median (MoM) values of mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), serum placental growth factor (PlGF) and serum soluble fms-like tyrosine kinase-1 (sFlt-1), and stratify women into high-, intermediate-and low-risk management groups. Methods This was a prospective observational study in women attending a second-trimester ultrasound scan at 19-24 weeks as part of routine pregnancy care. Patient-specific risks of delivery with PE < 32 weeks and < 36 weeks' gestation were calculated using the competing-risks model to combine the prior risk from maternal characteristics and medical history with MoM values of MAP, UtA-PI, PlGF and sFlt-1. On the basis of these risks, the population was stratified into high-, intermediate-and low-risk groups. Different risk cut-offs were used to vary the proportion of the population stratified into each risk category and the performance of screening for delivery with PE at < 32 weeks' gestation, at 32-35 weeks and at >= 36 weeks was estimated. In addition to empirical performance, we also derived model-based performance because the number of cases of PE delivering < 32 weeks was low. Results The study population of 7748 singleton pregnancies included 268 (3.5%) that subsequently developed PE. Using a risk cut-off of 1 in 100 for PE delivering < 32 weeks' gestation and a risk cut-off of 1 in 300 for PE delivering < 36 weeks, the proportion of the population stratified into high-, intermediate-and low-risk was 0.9%, 17.2% and 81.9%, respectively. The high-risk group contained 97% of pregnancies with PE < 32 weeks and 45% of those with PE at 32-35 weeks. The intermediate-risk group contained a further 46% of women with PE at 32-35 weeks. The low-risk group contained only 0.03% of pregnancies with PE < 32 weeks and 9% of those with PE at 32-35 weeks. Conclusion Risk stratification of PE by the combined test at 19-24 weeks' gestation can identify, first, a group which constitutes < 1% of the total population and contains > 95% of those that will develop PE < 32 weeks and are in need of intensive monitoring at 24-31weeks and, second, a group which constitutes < 20% of the total and contains > 90% of those that will develop PE at 32-35 weeks and are in need of reassessment at 32 weeks. Copyright (C) 2017 ISUOG. Published by John Wiley & Sons Ltd.