MATERNAL VASCULAR INDICES AT 36 WEEKS' GESTATION IN THE PREDICTION OF PREECLAMPSIA.

OBJECTIVE: To identify the most discriminatory maternal vascular index in the prediction of preeclampsia (PE) at 35-37 weeks' gestation, and to examine the performance of screening for PE by combinations of maternal risk factors and biophysical and biochemical markers at 35-37 weeks' gestation.

METHODS: This was a prospective observational non-intervention study in women attending for a routine hospital visit at 35+0 to 36+6 weeks' gestation. The visit included recording of maternal demographic characteristics and medical history, vascular indices and hemodynamic parameters obtained by a non-invasive operator independent device (pulse wave velocity, augmention index, cardiac output, stroke volume, central systolic and diastolic blood pressure, total peripheral resistance and fetal heart rate) mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), and serum concentration of placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLT-1). The performance of screening for delivery with PE at any time and at <3 weeks from assessment by a combination of maternal risk factors and various combinations of biomarkers was determined.

RESULTS: The study population comprised of 6,746 women with singleton pregnancies, including 176 (2.6%) who subsequently developed PE. There were three main findings. First, in women who developed PE, compared to those who did not, there were higher central systolic and diastolic blood pressure, pulse wave velocity (PWV), peripheral vascular resistance and augmentation index. Second, the most discriminatory indices were systolic and diastolic blood pressure and PWV, with poor prediction from the other indices. However, the performance of screening by a combination of maternal risk factors plus MAP was at least as high as that of a combination of maternal risk factors plus central systolic and diastolic blood pressure; consequently in screening for PE we used PWV, MAP, UtA-PI, PlGF and sFLT-1. Third, in screening for both PE within 3 weeks and PE at any time from assessment, the detection rate at 10% false positive rate of a biophysical test comprising of maternal risk factors plus MAP, UtA-PI and PWV (PE within 3 weeks: 85.2%, 95% CI 75.6 - 92.1%; PE at any time: 69.9%, 95% CI 62.5 - 76.6%) was not significantly different from a biochemical test utilizing the competing risks model to combine maternal risk factors with PlGF and sFLT-1 (PE within 3 weeks: 80.2%, 95%CI 69.9 - 88.3%; PE at any time: 64.2%, 95% CI 56.6 - 71.3%), and they were both superior to screening by low PlGF concentration (PE within 3 weeks: 53.1%, 95% CI 41.7 - 64.3%; PE at any time: 44.3, 95% CI 36.8 - 52.0%) or high sFLT-1 / PlGF concentration ratio (PE within 3 weeks: 65.4% 95% CI 54.0 - 75.7%; PE at any time: 53.4%, 95% CI 45.8 - 60.9%).

CONCLUSIONS: First, increased maternal arterial stiffness precedes the clinical onset of PE. Second, maternal PWV at 35-37 weeks' gestation in combination with MAP and UtA-PI, provides effective prediction of subsequent development of PE.