Can Fetal Heterotaxy Syndrome Be Diagnosed Through Prenatal Ultrasound in the First Trimester (GA 11+0-13+6 Weeks)?

Abstract

Objective: To investigate the value of prenatal ultrasonography in the diagnosis and classification of fetal heterotaxy syndrome (HS) in the first trimester (gestational age 11⁺⁰-13⁺⁶ weeks).

Methods: A retrospective analysis of data from 31 HS fetuses prenatally diagnosed with HS. Diagnoses were confirmed by follow-up prenatal ultrasound and in some cases postnatal ultrasound or autopsy. Data were collected on ultrasound characteristics of left atrial isomerism (LAI) and right atrial isomerism (RAI) in the first trimester, follow up ultrasounds, pregnancies outcomes, and postnatal ultrasound or autopsy findings, if available.

Results: In total, 23cases of HS were diagnosed in the first trimester, and 8 cases were missed during the GA 11⁺⁰-13⁺⁶ weeks ultrasound. The sensitivity, specificity, false positive rate, false negative rate, positive predictive value, and negative predictive value of prenatal ultrasound examination for fetal HS were 74.19%, 100%, 0, 25.80%, 100%, and 99.98%, respectively. The main and common manifestations of fetal HS included abnormal positioning of the stomach and heart and positioning of the stomach and umbilical vein (UV) on different sides, combined with complete atrioventricular septal defect (AVSD), double outlet of the right ventricle (DORV) and other CHDs. Compared with RAI, fetuses with LAI in the first trimester of pregnancy were more prone to bradycardia and ductus venous (DV) a-wave inversion (p < 0.05). Among the 31 HS cases, only 6 pregnancies were continued, resulting in one neonatal death and five liveborns with a good prognosis.

Conclusion: Ultrasound performed during GA 11⁺⁰-13⁺⁶ weeks can be an effective tool for diagnosing fetal HS, particularly when significant cardiovascular anomalies are present. However, fetal LAI without complex intracardiac malformations is more likely to be missed in diagnosis during the first trimester. Most cases of HS diagnosed in early pregnancy are associated with major intracardiac anomalies and result in termination of pregnancies.