Implementing Preeclampsia Screening in Switzerland (IPSISS): First Results from a Multicentre Registry.

Introduction: The Fetal Medicine Foundation (FMF) London developed a first trimester combined screening algorithm for preterm preeclampsia (pPE) that allows a significantly higher detection of pregnancies at risk compared to conventional screening by maternal risk factors only. The aim of this trial is to validate this screening model in the Swiss population in order to implement this screening into routine first trimester ultrasound and to prescribe low-dose aspirin 150 mg (LDA) in patients at risk for pPE. Therefore, a multicentre registry study collecting and screening pregnancy outcome data was initiated in 2020; these are the preliminary results.

Methods: Between June 1, 2020, and May 31, 2021, we included all singleton pregnancies with pPE screening at the hospitals of Basel, Lucerne, and Bern. Multiple of medians of uterine artery pulsatility index (UtA-PI), mean arterial pressure (MAP), placental growth factor (PlGF), and pregnancy-associated plasma protein A (PAPP-A) as well as risks were analysed as calculated by each centre's software and recalculated on the FMF online calculator for comparative reasons. Statistical analyses were performed by GraphPad Version 9.1.

Results: During the study period, 1,027 patients with singleton pregnancies were included. 174 (16.9%) had a risk >1:100 at first trimester combined screening. Combining the background risk, MAP, UtA-PI, and PlGF only, the cut-off to obtain a screen positive rate (SPR) of 11% is ≥1:75. Outcomes were available for 968/1,027 (94.3%) of all patients; 951 resulted in live birth. Fifteen (1.58%) developed classical preeclampsia (PE), 23 (2.42%) developed PE according to the International Society for the Study of Hypertension in Pregnancy (ISSHP) definition.

Conclusion: First trimester combined screening for PE and prevention with LDA results in a low prevalence of PE. The screening algorithm performs according to expectations; however, the cut-off of >1:100 results in a SPR above the accepted range and a cut-off of ≥1:75 should be considered for screening. More data are needed to evaluate, if these results are representative for the general Swiss population.