Proposed clinical management of pregnancies after combined screening for pre-eclampsia at 35-37 weeks' gestation

Objective: To estimate the patient-specific risk of preeclampsia (PE) at 35-37 weeks’ gestation by a combination of maternal characteristics and medical history with multiple of the median (MoM) values of mean arterial pressure (MAP), uterine artery pulsatility index (UTPI), 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.<br /><br />Methods: This was a prospective observational study in women attending for a third-trimester ultrasound scan at 35-37 weeks as part of routine pregnancy care. Patient-specific risks of delivery with PE at <4 weeks from assessment and PE at <42 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, UTPI, 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 <40 and >40 weeks’ gestation was estimated.<br /><br />Results: The study population of 3,703 singleton pregnancies included 38 (1.0%) with PE at <40 weeks’ gestation and 22 (0.6%) with PE at >40 weeks. Using a risk cut-off for PE<br />at <4 weeks of 1 in 50 to define the high-risk group and a risk cut-off of <1 in 100 for PE at <42 weeks’ gestation to define the low-risk group, the proportion of the population<br />stratified into high-, intermediate- and low-risk was about 12.7%, 28.8% and 58.5%, respectively. The high-risk group contained 92% of pregnancies with PE at <40 weeks’ gestation and 73% of those with PE at >40 weeks. The intermediate-risk group contained a further 27% of women with PE at >40 weeks. In the low-risk group, none of the women developed PE at <40 or >40 weeks’ gestation.<br /><br />Conclusion: The study presents risk stratification of PE by the combined test at 35-37 weeks aiming to identify a high-risk group in need of intensive monitoring from the time of<br />the initial assessment and up to 40 weeks’ gestation, an intermediate-risk group in need of reassessment at 40 weeks’ gestation and a low-risk group which can be reassured that<br />they are unlikely to develop PE.