Prenatal diagnosis of CHD is essential for counseling, perinatal management, and planning surgical strategies. Data from southern Chile are scarce.

We conducted a retrospective, observational, descriptive study of all cases with a confirmed prenatal diagnosis of moderate or complex CHD at the Fetal Exploration Unit, Guillermo Grant Benavente Hospital, between January 2018 and March 2025. Maternales variables, fetal echocardiographic findings, genetic studies, and neonatal outcomes were analysed. Survival was estimated using Kaplan–Meier curves.

Eighty cases were analysed, one with complete atrioventricular block requiring pacemaker implantation and 79 with structural CHD. Male fetuses accounted for 63.8%. The most frequent entities were isolated or associated transposition of the great arteries (24.1%), hypoplastic left heart syndrome (16.5%), and coarctation of the aorta (10.1%). Twenty-one diagnostic combinations (26.6%) were documented, the most common being double-outlet right ventricle with transposition of the great arteries. Genetic testing was performed in 39 cases (48.8%), revealing chromosomal anomalies in 13 (16.3%). Maternal comorbidities were recorded in 27 pregnancies (33.8%), notably diabetes and hypothyroidism. Seventy percent of patients underwent neonatal cardiac surgery. Seventeen deaths (21.3%) occurred: one stillbirth and 16 postnatal deaths, of which 13 were neonatal. Overall survival at follow-up was 78.8%. Kaplan–Meier analysis showed a marked drop in the first month of life, stabilising thereafter at ∼81%.

Findings highlight a high prevalence of critical lesions, a relevant proportion of chromosomal abnormalities, and a notable association with maternal hypothyroidism. Survival reflects advances in prenatal diagnosis and neonatal cardiac surgery, although challenges remain for non-surgical cases.

To evaluate the diagnosis, clinical features, management and post-natal follow-up in consecutive fetuses identified with tachycardia.

We reviewed consecutive fetuses with tachycardia identified in a single tertiary institution between January, 2001, and December, 2008. We considered several options for management, including no treatment but close surveillance, trans-placental antiarrhythmic therapy in fetuses presenting prior to 36 weeks of gestation, and delivery and treatment as a neonate for fetuses presenting after 36 weeks of gestation. Data was gathered by a review of prenatal and postnatal documentation.

Among 29 fetuses with tachycardia, 21 had supraventricular tachycardia with 1 to 1 conduction, 4 had atrial flutter, 3 had atrial tachycardia, while the remaining fetus had ventricular tachycardia. Of the group, 8 fetuses (27.6%) were hydropic. Transplacental administration of antiarrhythmic drugs was used in just over half the fetuses, delivery and treatment as a neonate in one-quarter, and no intervention but close surveillance in one-sixth of the case. Twenty-six of 29 fetuses (89.7%) were born alive. Only patients with fetal hydrops suffered mortality, with 37.5% of this group dying, this being statistically significant, with the value of p equal to 0.03, when compared to non-hydropic fetuses. Only 3 patients (11.5%) were receiving antiarrhythmic prophylaxis beyond the first year of life.

A significant proportion of fetal tachycardias recognized before 36 weeks of gestation can be treated successfully by transplacental administration of antiarrhythmic drugs. Fetuses presenting after 36 weeks of gestation can be effectively managed postnatally. The long-term prognosis for fetuses diagnosed with tachycardia is excellent, with the abnormal rhythm resolving spontaneously during the first year of life in most of them.