Congenital diaphragmatic hernia is a malformation of the diaphragm caused when the space between the abdomen and the chest cavity does not close by the ninth or tenth week of pregnancy. The incidence rate of congenital diaphragmatic hernias ranges between 1 in 3,000 and 1 in 5,000 live births. When including intrauterine deaths, and neonatal deaths, the incidence rate is an estimated 1 in 2,200.
85-90% of congenital diaphragmatic hernias occur on the left side, 10-15% occur on the right side, and 2% occur on both sides. 60% of congenital diaphragmatic hernias are considered non-syndromic, meaning they occur as an isolated malformation. The remaining 40% are considered syndromic, meaning that they occur in conjunction with another diagnosis. Congenital diaphragmatic hernias that are associated with other diagnoses have a higher mortality rate than isolated cases of the condition.
There are a dozen single-gene disorders associated with congenital diaphragmatic hernias. 25-57% of all cases of congenital diaphragmatic hernias are associated with anomalies such as anencephaly, congenital heart defects, hydrocephalus, pulmonary hypoplasia, and renal agenesis. 10-20% of congenital diaphragmatic hernias are associated with aneuploidy, or chromosomal abnormalities, such as trisomy 13, trisomy 18, and trisomy 21 (Down syndrome). 95% of cases of congenital diaphragmatic hernias that result in stillbirth have associated anomalies.
The recurrence risk for congenital diaphragmatic hernias is entirely dependent on whether the condition is syndromic or isolated. True isolated cases of congenital diaphragmatic hernias have a recurrence risk of 2%. Fetal karyotyping and parental genetic testing are recommended.