Effectiveness of Routine Third Trimester Ultrasonography to Reduce Adverse Perinatal Outcomes in Low-risk Pregnancy (the IRIS Study): Nationwide, Pragmatic, Multicentre, Stepped Wedge Cluster Randomized Trial

Abstract

(BMJ. 2019;367:l5517) Fetal growth restriction affects 7% to 10% of pregnancies and is a major risk factor for perinatal morbidity and death, as well as cardiovascular disease in adulthood. Small for gestational age (SGA) infants can be detected during usual prenatal care with serial fundal height measurements. While routine ultrasonography during the third trimester more frequently detects SGA infants than usual prenatal care, there is a lack of evidence indicating this practice reduces the incidence of severe adverse perinatal outcomes. Previous studies on the subject have been underpowered or were not clearly linked with appropriate management practices following an SGA diagnosis. This Intrauterine growth restriction Risk Selection (IRIS) study developed a multidisciplinary protocol for detecting and managing suspected fetal growth restriction and used a stepped wedge cluster randomized design to evaluate the effectiveness of routine ultrasonography in the third trimester combined with usual care, compared with usual care alone, in decreasing severe adverse perinatal outcomes.