Understanding a CDH Diagnosis: The Basics

Hearing that your baby has Congenital Diaphragmatic Hernia (CDH) is overwhelming. It is important to know right away that this is a structural issue that occurs very early in pregnancy—it is not something you caused by anything you did, ate, or experienced ^[1][2]. CDH happens to about 1 in every 2,500 to 3,000 live births, making it one of the more common major birth defects. While it is a very serious condition, with modern medical care, overall survival rates are generally between 70% and 80% ^[3].

This resource guide is designed to help you navigate your baby’s care journey. You can explore the following topics to learn more:

• Anatomy and Subtypes: Bochdalek, Morgagni, and Genetics
• Prenatal Scans and Prognosis: Decoding O/E LHR and Liver Position
• Prenatal Interventions: Is FETO Right for Your Baby?
• The Delivery and NICU Journey: Stabilization and ECMO
• The Surgical Repair: Timing, Options, and Patches
• Bringing Baby Home: Long-Term Survivorship and Monitoring

What is CDH?

In simple terms, CDH is a hole in the diaphragm, which is the thin muscle that separates the chest from the abdomen. Because of this hole, organs that should stay in the belly—like the stomach, intestines, and liver—can move up into the chest.

When these organs move into the chest, they take up space where the lungs need to grow. This leads to two main challenges:

• Pulmonary Hypoplasia: The lungs are smaller than they should be because they didn’t have enough room to grow.
• Pulmonary Hypertension: The blood vessels in the lungs may be underdeveloped, leading to high blood pressure in the lungs, which makes it harder for the baby to get oxygen after birth.

The “Dual-Hit” Hypothesis

Doctors often use the dual-hit hypothesis to explain why the lungs are affected in CDH. Think of it as two separate events that impact lung growth:

1. The First Hit: Very early in development, the same genetic or molecular “glitch” that prevents the diaphragm from closing also impacts the very beginning of lung growth. This means the lungs might start off slightly smaller even before the hole is fully formed ^[4][5].
2. The Second Hit: Once the hole in the diaphragm exists, the abdominal organs move up into the chest and physically crowd the lungs. This mechanical pressure is the “second hit” that further restricts how much the lungs can grow for the rest of the pregnancy ^[4][6].

Understanding this helps explain why the severity of CDH can vary so much from one baby to another ^[7].

Isolated vs. Complex CDH

Your medical team will look closely to see if your baby has “isolated” or “complex” (syndromic) CDH. This distinction helps them plan the best possible care.

• Isolated CDH (approx. 60% of cases): This means the CDH is the only major health issue identified. These babies generally have the best outlook because their other organs, like the heart, are developing normally ^[8].
• Complex or Syndromic CDH (approx. 40% of cases): This means the baby has CDH along with other health challenges, such as a heart defect or a genetic syndrome ^[8][9]. In these cases, a genetic counselor is usually a key part of the team to help identify any underlying causes ^[10][11].

Because CDH affects both the structure of the body and the function of the lungs, it requires a multidisciplinary care team—a group of specialists working together. Your team’s goal is to provide a highly coordinated plan from the moment of diagnosis through delivery and beyond ^[3].