Altres ajuts: The study is partially made possible by support of the 'Programme Hospitalier de Recherche Clinique and 'La Foundation de la Recherche Médicale (grant number DEQ20170336759, France). M.T. was supported by the Polish Mothers Memorial Hospital Research Institute (internal grant number 2016/IV/54-GW. LvdZ is supported by a Kolff grant from the Dutch Kidney Foundation (13OKJ36) and a ZonMW-VENI grant from the Netherlands Organisation for Scientific Research (91618036). This project has been supported by ERN ERKNet and ERN eUROGEN, which are partly co-funded by the European Union within the framework of the Third Health Programme 'ERN-2016-Framework Partnership Agreement 2017-2021'.

Posterior urethral valves (PUV) account for 17% of paediatric end-stage renal disease. A major issue in the management of PUV is prenatal prediction of postnatal renal function. Fetal ultrasound and fetal urine biochemistry are currently employed for this prediction, but clearly lack precision. We previously developed a fetal urine peptide signature that predicted in utero with high precision postnatal renal function in fetuses with PUV. We describe here the objectives and design of the prospective international multicentre ANTENATAL (multicentre validation of a fetal urine peptidome-based classifier to predict postnatal renal function in posterior urethral valves) study, set up to validate this fetal urine peptide signature. Participants will be PUV pregnancies enrolled from 2017 to 2021 and followed up until 2023 in >30 European centres endorsed and supported by European reference networks for rare urological disorders (ERN eUROGEN) and rare kidney diseases (ERN ERKNet). The endpoint will be renal/patient survival at 2 years postnatally. Assuming α = 0.05, 1-β = 0.8 and a mean prevalence of severe renal outcome in PUV individuals of 0.35, 400 patients need to be enrolled to validate the previously reported sensitivity and specificity of the peptide signature. In this largest multicentre study of antenatally detected PUV, we anticipate bringing a novel tool to the clinic. Based on urinary peptides and potentially amended in the future with additional omics traits, this tool will be able to precisely quantify postnatal renal survival in PUV pregnancies. The main limitation of the employed approach is the need for specialized equipment. Accurate risk assessment in the prenatal period should strongly improve the management of fetuses with PUV.