OC09.07: Isolated D‐transposition of great arteries: the shifted trend in live‐born incidence

To evaluate time trends in incidence, detection rate, gestational age at diagnosis and termination of pregnancy (TOP) rate in fetuses with transposition of great arteries (TGA). This is a single tertiary centre, population-based, retrospective, observational study. We included 32,320 live-born neonates and the pregnancies resulting in terminations due to the diagnosis of TGA, in two cohorts (2008 - 2013 and 2018 - 2023). Patient records on TOPs and neonates with TGA were reviewed to validate the diagnoses. Of 256 neonates and fetuses diagnosed with congenital heart and great vessels abnormalities, 213 had major congenital heart diseases. In the historical cohort, the prevalence of MCHD was 0.54%, and in the recent cohort - 0.79%. For TGA, the median gestational age at the prenatal diagnosis was 29.3 weeks (mean 25.4) in the historical cohort and – respectively, 13.4 weeks (mean 17.2) in the recent one. Postnatally, the diagnosis was reached at 2,6 days of life. During the two periods studied, the global incidence of TGA (including TOPs) was comparable (0.039 vs 0.054%)(p = 0.557 > 0.05); it increased slightly over time. The total prenatal detection rate of TGA didn't significantly change if comparing the two periods (71.42% vs 87.5%) (p = 0.438 > 0.05). Cases diagnosed in the first and second trimester (FT/ST) of pregnancy increased from 28.54% (2008-2013) to 75% (2018-2023) (p = 0.072). The TOP rate of TGA significantly increased from 14.28% to 75% (p = 0.019 < 0.05) in our setting. The live-born incidence of TGA decreased (from 0.34% to 0.013%) (p = 0.238 > 0.05). Detection rates of TGA improved during the study, and the median gestational age at the diagnosis significantly decreased. The increased detection of TGA during the first and second trimesters of pregnancy has led to a significantly increased termination rate and a subsequent decrease in the live-birth incidence of TGA.