[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Heart and vessels](https://durgical.com/en/embryology/#a-heart) › Transposition of the great arteries

[Embryology](https://durgical.com/en/embryology/) · [Heart and vessels](https://durgical.com/en/embryology/#a-heart)

# Transposition of the great arteries

- Malformation

The aorta arises from the right ventricle and the pulmonary trunk from the left: oxygen-poor blood goes back to the body and the baby is born very blue.

Updated 2026-11-01

**See it in 3D:** [Ascending aorta](https://durgical.com/en/anatomy/ascending-aorta/) · [Pulmonary trunk](https://durgical.com/en/anatomy/pulmonary-trunk/) · [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/) · [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/) · [Interatrial septum](https://durgical.com/en/anatomy/interatrial-septum/) · [Ligamentum arteriosum](https://durgical.com/en/anatomy/ligamentum-arteriosum/)

## Key points

- Cause: the aorticopulmonary septum fails to spiral (abnormal neural crest migration).
- Parallel circulations: incompatible with life without mixing (ASD, ductus arteriosus, VSD).
- Cyanotic from day one; the most common cyanotic defect of the newborn.
- Prostaglandins keep the ductus open; balloon atrial septostomy improves mixing.
- Chest X-ray: egg-shaped heart with a narrow pedicle ('egg on a string').
- Associated with maternal diabetes.

## What it is

In transposition of the great arteries (d-TGA) the aorticopulmonary septum grows straight instead of spiraling, so the aorta connects to the right ventricle and the pulmonary trunk to the left. The two circulations run in parallel, and survival depends on mixing through the foramen ovale, the ductus arteriosus or a VSD. It is the most common cyanotic heart defect in newborns.

## Embryological cause

- Weeks 5–7: the truncal and conal ridges grow straight, without the normal 180-degree twist.
- The straight septum connects the anterior aorta to the right ventricle and the posterior pulmonary trunk to the left.
- Associated with abnormal migration or function of cardiac neural crest and the second heart field.
- The rest of the heart (atria, ventricles, AV valves) is usually well formed.

## Markers

- Cardiac neural crest
- Maternal diabetes

## How it presents

- Intense cyanosis in the first hours that does not improve with oxygen.
- There may be no murmur if the ventricular septum is intact.
- If the ductus closes, hypoxemia and acidosis worsen quickly.
- With a large VSD cyanosis is milder but early heart failure appears.

## Diagnosis

- Prenatal echocardiography: the great arteries leave in parallel instead of crossing.
- Newborn pulse oximetry.
- Chest X-ray: 'egg on a string' from the narrow upper mediastinum.

## Memory aid

Two closed loops that never touch: the baby survives only while a door stays open for blood to cross from one loop to the other.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the embryological cause of transposition of the great arteries?

The aorticopulmonary septum grows straight instead of spiraling, so the aorta connects to the right ventricle.

## Why does a newborn with transposition depend on the ductus arteriosus?

The circulations are in parallel, and the ductus (with the foramen ovale) lets oxygenated blood mix.

## Which maternal factor is associated with transposition?

Poorly controlled maternal diabetes.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/embryology/transposition-of-the-great-arteries/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Ascending aorta](https://durgical.com/en/anatomy/ascending-aorta/)
- [Pulmonary trunk](https://durgical.com/en/anatomy/pulmonary-trunk/)
- [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/)
- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)
- [Interatrial septum](https://durgical.com/en/anatomy/interatrial-septum/)
- [Ligamentum arteriosum](https://durgical.com/en/anatomy/ligamentum-arteriosum/)

## Related

- [Outflow tract: the spiral aorticopulmonary septum and neural crest](https://durgical.com/en/embryology/outflow-tract-the-spiral-aorticopulmonary-septum-and-neural-crest/)
- [Tetralogy of Fallot](https://durgical.com/en/embryology/tetralogy-of-fallot/)
- [Persistent truncus arteriosus](https://durgical.com/en/embryology/persistent-truncus-arteriosus/)
- [Patent ductus arteriosus](https://durgical.com/en/embryology/patent-ductus-arteriosus/)
- [Atrial septal defect and patent foramen ovale](https://durgical.com/en/embryology/atrial-septal-defect-and-patent-foramen-ovale/)
- [Maternal diabetes and obesity as teratogens](https://durgical.com/en/embryology/maternal-diabetes-and-obesity-as-teratogens/)

## Related conditions

- [Transposition of the great arteries](https://durgical.com/en/conditions/transposition-of-the-great-arteries/)

[← All of embryology](https://durgical.com/en/embryology/)

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Langman's Medical Embryology, 13th ed., ch. 13: Cardiovascular System (Wolters Kluwer, 2015); [Dextro-Transposition of the Great Arteries (d-TGA) | Congenital Heart Defects (CHDs) | CDC](https://www.cdc.gov/heart-defects/about/d-tga.html) (Centers for Disease Control and Prevention, 2024).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/embryology/transposition-of-the-great-arteries/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/transposition-of-the-great-arteries/