2.1

Study design

This study was designed as a case-control analysis, following the methodology of the Latin American Collaborative Study of Congenital Malformations (ECLAMC), a clinical and epidemiological research program recognized by the World Health Organization as a Collaborating Center for the Prevention of Congenital Malformations [ ]. The aim was to analyze all birth defects reported to the PREVERDEC surveillance system to identify cases of transposition of the great vessels (TGV).

Data was collected by certified physicians working in 43 hospitals in Bogotá and Cali, Colombia. Based on previous statistics, the PREVERDEC system is estimated to cover 59.3 % of all births in Bogotá and Cali during the study period [ ]. While this robust network provides a significant dataset, some births may occur outside institutional settings or in hospitals not participating in the surveillance system, which introduces the possibility of underreporting. The databases, which followed medical standards, were provided by Pontificia Universidad Javeriana and the Bogotá Secretary of Health.

2.2

Study participants

The study included live births and stillbirths diagnosed with TGV, with a birth weight >500 g, born in healthcare institutions linked to the surveillance program between 2003 and 2019. The healthcare institutions represented a range of complexity levels (low, moderate, and high) and included both public and private sectors, ensuring a sample representative of the country’s population. The institutions were located in some of the most densely populated areas, thus receiving patients from across the nation. A case-to-control ratio of 1: 4 was employed, with controls selected as live births without congenital anomalies, matched by birth date and healthcare institution.

Cases of TGV were identified and classified using the ECLAMC coding system. Cases were further categorized into four subgroups: isolated cases (only TGV was present), complex cases (TGV with other cardiovascular anomalies), cases with multiple congenital anomalies (TGV with non-cardiovascular defects), and syndromic cases (cases with a recognized genetic syndrome). Associated congenital heart defects in complex cases were described based on available clinical and diagnostic data.

2.3

Statistical analysis

The prevalence of transposition of the great vessels was calculated as a rate of live birth cases per 10,000 live births, and the results were reported with a 95 % confidence interval using the Poisson distribution. Prevalence was used as the selected measure of frequency, with live births as the denominator, according to previous consensus in the field of birth defects [ ]. As for demographic data, the following continuous variables were analyzed: maternal age, gestational age, previous pregnancies, birth weight and height. Nominal variables included were newborn sex, previous abortions, and multiple pregnancy. Continuous variables were analyzed by comparison of means with their corresponding standard deviation, whilst nominal variables were analyzed by frequency comparison.

To assess risk factors for TGV, odds ratios (OR) with 95 % CIs were calculated for birth weight (<2500 g), birth height (<40 cm), gestational age (<37 weeks), newborn sex, maternal and paternal age (>35 years), and pregnancy-related factors such as pregestational and gestational diabetes, folic acid consumption, drug use, and tobacco use. Socioeconomic status was classified using the Colombian National Department of Statistics methodology, comparing low socioeconomic status (1 and 2) to medium-high status (3 to 6). Data was organized using Microsoft Excel 2021 and analyzed in IBM SPSS Statistics. Odds ratios were calculated without adjusting for matching of cases and controls.

The study received a waiver for ethical approval from the local Ethics Committee of Pontificia Universidad Javeriana, considering its retrospective nature and the fact that all procedures performed were part of routine care. The assigned approval code was FM-CIE-8324-14.