Study protocol for a descriptive analysis of non-invasive prenatal testing uptake and performance in singleton and twin pregnancies using Ontario birth registry data.

Introduction: Despite the availability of funded first-tier non-invasive prenatal testing (NIPT) for twin pregnancies in Ontario, Canada, research gaps persist regarding the feasibility and effectiveness of NIPT in this demographic. This protocol documents our planned comprehensive overview of twin data from the large Ontario provincial registry and evaluates the performance of NIPT among singleton and twin pregnancies.

Methods And Analysis: We will conduct a descriptive study using routinely collected data housed in the Better Outcomes Registry & Network Ontario. The study population will include all singleton and twin pregnancies with an estimated date of delivery between 1 September 2016 and 31 March 2023. We will compare patient characteristics, NIPT uptake and test performance metrics (including sensitivity, specificity, positive predictive value and negative predictive value) between singleton and twin pregnancies. Subgroup analyses will be conducted, including assessment by the mode of conception, trimester of initial screening, age of the pregnant individual and eligibility for publicly funded first-tier NIPT.

Ethics And Dissemination: This study has received approval from the Research Ethics Boards of the Children's Hospital of Eastern Ontario (24/01PE) and the University of Ottawa (H-04-24-10309). Results will be disseminated through scientific conferences and publication in a peer-reviewed journal. By making our protocol and findings publicly available, we aim to establish a foundational reference for future investigations in Ontario. Additionally, we seek to support the design and implementation of further studies on NIPT in twin pregnancies in Canada and elsewhere.