Screening tests for trisomy 21 have gradually become more refined and now involve complex statistical models that combine demographic, biophysical, and biochemical parameters to produce individualized risk estimates for pregnant women. An understanding of the evolution of the principles, methods, and statistical techniques applied to Down syndrome screening is valuable as these processes can be transferred to other, more prevalent, adverse pregnancy outcomes. First trimester ultrasound forms the foundation of this process.
*RPA Women and Babies, Royal Prince Alfred Hospital
†Discipline of Obstetrics, Gynaecology and Neonatology, Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
‡Fetal Medicine Foundation USA
§Division of Maternal Fetal Medicine, Wright State University, Dayton, Ohio
The authors declare that they have nothing to disclose.
Correspondence: Jon Hyett, MD, RPA Women and Babies, Royal Prince Alfred Hospital, Camperdown, Sydney, NSW, Australia. E-mail: firstname.lastname@example.org