Prematurity Significantly Impacts Mortality in Congenital Diaphragmatic Hernia

Preterm birth accounts for nearly a quarter of mortality in babies with congenital diaphragmatic hernia (CDH), according to a new study from Children’s Hospital Los Angeles.

The study, led by Kuan-Chi Lai, MD, MPH, found that, at a population level, 24% of mortality in babies with CDH can be attributed to being born premature. The impact of prematurity is particularly significant for late preterm infants—those born at 34-36 weeks’ gestation.

Dr. Lai, a neonatologist in the Fetal and Neonatal Institute at Children’s Hospital Los Angeles, presented the results in May at the 2024 Pediatric Academic Societies meeting in Toronto.

“What this suggests is that safely extending pregnancy could improve overall survival rates for babies with congenital diaphragmatic hernia,” he says. “That’s easier said than done. But finding ways to do that is the next step in research.”

Prematurity and CDH

At Children’s Hospital Los Angeles, the Level IV Steven & Alexandra Cohen Foundation Newborn and Infant Critical Care Unit (NICCU) sees the most complex and critically ill babies—including many with the most severe forms of congenital diaphragmatic hernia.

CDH occurs when the diaphragm does not properly close during development, allowing abdominal organs such as the intestines to migrate into the chest area. This affects a baby’s lung development and can cause breathing issues and other problems.

And while survival rates for CDH have improved over the years, mortality remains high. These babies are also more likely to be born premature.

To find out how much prematurity is contributing to overall one-year mortality rates in these babies, Dr. Lai and the team conducted a retrospective cohort analysis using the Pediatric Health Information System database, which includes 45 pediatric hospitals across the U.S.

The study included 2,328 neonates with CDH born between 2016 through the end of 2021. Researchers grouped babies by gestational age, with 34% born full term, 38% early term and 28% preterm.

Key findings

The team found that:

• Overall, prematurity accounted for 24% of mortality in babies with CDH.
• Extremely preterm babies (those born between 22 and 27 weeks) had the highest mortality risk—3.55 times higher than a full-term baby with CDH.
• Babies born at 34 to 36 weeks still had double the mortality risk of a full-term baby. This late preterm group was also much larger—467 patients, versus just 18 who were born extremely preterm.
• As a result, prematurity in late preterm infants accounted for 13.7% of mortality among all babies born with CDH.

“We usually think that being born just a few weeks early has substantially less impact on mortality than earlier preterm birth,” Dr. Lai says. “But our study found that late preterm CDH patients have twice the mortality risk as full-term babies with CDH, and this group is fairly significant in size. So on a population level, addressing prematurity in this late preterm group could help improve survival rates for babies with CDH.”

Study authors were Kuan-Chi Lai, MD, MPH; Molly Easterlin, MD, MS; Rachel Chapman, MD; and Philippe Friedlich, MD, MSEpi, MBA.