Early onset pre-eclampsia (ePET) requiring delivery, on maternal grounds, before 34 weeks’ gestation is common, affecting 0.5% of pregnancies. Whilst this represents only 10% of the spectrum of disease, this includes the majority of neonatal admissions and a disproportionate amount of maternal mortality and morbidity (>30% of maternal ITU admissions) related to hypertensive disease. The phenotype of ePET is related to placenta insufficiency that results from poor implantation of the trophoblast. The hypoxic placenta produces local hormones and tissue mediators that impact the maternal vascular endothelium leading to peripheral vasoconstriction (hypertension) and end organ damage. This two-stage disease process can be interrupted and this is the basis of screening for prevention of disease.
Women are already routinely screened at 12 weeks and this test provides the foundation of screening for ePET. Women already attend, trained sonographers that produce quality assured measurements are available, biochemical assays that reflect trophoblast function are already in place and the complex mechanism of risk analysis, allowing for population differences in test characteristics have been defined. Screening for ePET requires measurement of two additional parameters; uterine artery PI (by ultrasound) and mean arterial pressure. A UK based screening algorithm that has 90% sensitivity and 90% specificity for ePET has been validated in an Australian population.1 Addition of the biochemical marker PlGF would allow further improvement in efficacy to specificity of 95%. The performance of this test is vastly superior to that of traditional screening (based on maternal history): [ROC AUC Hx 0.748; ROC AUC RPA algorithm 0.919; p=0.0002].
Prophylactic administration of aspirin is effective in reducing the risk of pre-eclampsia. Early intervention is important being associated with 50% reduction in the prevalence of severe/preterm disease. In our own cohort study, including 5,700 women, we prescribed 150mg Aspirin (nocte) to those deemed to be at high risk of ePET using the first trimester multivariate algorithm. The prevalence of disease was reduced by 90%.2 280 women were screened and 28 women treated to prevent one case of ePET. None of the women treated with aspirin had a placental abruption. The cost savings, primarily through reduced neonatal care, within a unit delivering 5,000 women a year, have been conservatively estimated to be $1,000,000 per year. National adoption of this strategy could prevent 1,200 cases of ePET a year with 67,000 fewer neonatal bed days per year.