Factors Associated with Gestational Week of Diagnosis Among Pregnancies with Prenatally Recognized Congenital Heart Disease: A Tertiary Referral-Centre Cohort Study

Background: Prenatal diagnosis of congenital heart defects (CHD) is important for perinatal planning, yet the gestational week at which CHD is diagnosed varies considerably. In referred cohorts, diagnostic timing may be influenced by maternal, fetal, temporal, and lesion-specific factors. This study examined factors associated with the gestational week of prenatal diagnosis among pregnancies with prenatally recognized and subsequently confirmed CHD referred to a national tertiary fetal cardiology centre. Methods: This study analyzed 833 pregnancies with confirmed CHD managed between 2005 and 2020. The primary outcome was the gestational week of prenatal diagnosis. Univariable associations with binary predictors were assessed using Student’s t-test, Welch’s t-test, or the Mann–Whitney U test according to distributional assumptions. A primary fully adjusted multivariable linear regression model with heteroscedasticity-robust standard errors was used to evaluate variables associated with the gestational week of diagnosis. The model included maternal age, calendar year as a continuous variable, twin pregnancy, amniotic fluid abnormalities, chromosomal status, and selected lesion-specific diagnoses. Chromosomal status was modelled hierarchically as no chromosomal abnormality, Down syndrome, or other chromosomal abnormality. Results: In univariable analyses, advanced maternal age, Down syndrome, and chromosomal abnormalities were associated with earlier diagnosis, whereas oligohydramnios was associated with later diagnosis. In the primary fully adjusted multivariable model, increasing maternal age was associated with earlier diagnosis (β = −0.169 weeks per year, 95% CI −0.238 to −0.099; p < 0.001), as was later calendar year (β = −0.211 weeks per year, 95% CI −0.311 to −0.111; p < 0.001). Coarctation of the aorta/aortic arch stenosis (β = 2.276 weeks, 95% CI 0.787 to 3.764; p = 0.003), pulmonary stenosis (β = 1.996 weeks, 95% CI 0.376 to 3.617; p = 0.016), and oligohydramnios (β = 2.097 weeks, 95% CI 0.228 to 3.965; p = 0.028) were associated with later prenatal diagnosis. Down syndrome showed a borderline association with earlier diagnosis (β = −1.350 weeks, 95% CI −2.702 to 0.002; p = 0.050). The model explained 12.2% of the variability in the gestational week of diagnosis, with an adjusted R2 of 0.107. Conclusions: In this tertiary referral-centre cohort of pregnancies with prenatally recognized and confirmed CHD, the gestational week of prenatal diagnosis was associated with maternal age, calendar year, oligohydramnios, and selected lesion-specific diagnoses. These findings should be interpreted as observational associations within an already recognized referral cohort rather than determinants of prenatal CHD detection in the general pregnant population. Future studies should incorporate referral pathways, screening history, ultrasound quality, operator experience, fetal position, and lesion-specific imaging characteristics to better characterize factors influencing the timing of prenatal CHD diagnosis.