Re: First-trimester risk assessment based on ultrasound and cell-free DNA vs combined screening: a randomized controlled trial. K. O. Kagan, R. Sroka, J. Sonek, H. Abele, K. Lüthgens, M. Schmid, P. Wagner, S. Brucker, D. Wallwiener and M. Hoopmann. Ultrasound Obstet Gynecol 2018; 51: 437-444