Implementation of routine first-trimester combined screening for preeclampsia based on the Gaussian algorithm: A clinical effectiveness study.

Objective: To evaluate the clinical effectiveness of the routine first-trimester screening for preeclampsia (PE) after being implemented in six Catalan maternities.

Methods: Participants in the reference group were recruited prospectively between October 2015 and September 2017. Participants in the study group were recruited retrospectively between November 2018 and May 2019, after implementing the screening program.