Prenatal Lung Size Now Reaches Beyond Survival Risk in Isolated CDH
In isolated left-sided congenital diaphragmatic hernia, the observed-to-expected lung-to-head ratio, or O/E LHR, may help forecast a surgical problem that often announces itself only after birth: the need for delayed abdominal closure. The preprint analyzed neonates treated between 2015 and 2026 and found that this prenatal marker, long used to grade pulmonary hypoplasia and overall severity, also tracked closely with whether the abdominal wall could be closed primarily after repair.
The cohort was small but clinically focused. Forty-five neonates with isolated left CDH were included, 28 in the primary closure group and 17 in the delayed abdominal closure group. The two groups were not interchangeable at baseline or after delivery. Infants who later required delayed closure had lower gestational age, higher rates of liver herniation, greater ECMO requirement, and higher mortality than those who underwent primary closure, with all comparisons reaching statistical significance.
One number stands out. The discriminative performance of O/E LHR for delayed abdominal closure reached an area under the ROC curve of 0.939.
Why a Lung Measure Can Signal an Abdominal Closure Problem
That association makes biological sense. In CDH, a smaller fetal lung relative to head size reflects more severe thoracic compression and less reserve at birth. When the thorax is already constrained, the postnatal operation does not end at diaphragmatic repair. Surgeons still have to return abdominal viscera to a cavity that may be too small to accept them without dangerous tension on the abdominal wall. A fetus with a more severe lung deficit is often the infant who arrives with the tightest thoracoabdominal mechanics, the greatest need for cardiopulmonary support, and the least tolerance for forced closure.
The study used a bootstrap-aggregated approach to identify an optimal prenatal threshold. The cut-off was 34.1% for O/E LHR. At that point, sensitivity reached 82.35% and specificity 82.14%. Positive predictive value was 73.68%, while negative predictive value was 88.46%. In plain clinical terms, a higher O/E LHR did not eliminate risk, but a lower value signaled a meaningful chance that the abdomen would not close safely on the first operation.
The multivariable analysis strengthened the signal. After adjustment for liver herniation, O/E LHR remained independently associated with delayed closure, with an odds ratio of 0.821 and a 95% confidence interval of 0.668 to 0.939. Each decrement in the ratio therefore moved the risk in the unfavorable direction, even after one of the most familiar anatomic severity markers was taken into account.
Surgical Planning Could Shift Earlier in the Pathway
This is where the finding becomes clinically useful. Antenatal counseling in CDH already centers on respiratory prognosis, ECMO probability, and the likelihood of complex neonatal care. A prenatal marker that also predicts delayed abdominal closure could change the tone of that discussion. Families and neonatal teams may need to prepare not only for ventilatory instability, but also for the possibility of staged surgery, temporary abdominal strategies, and a more prolonged postoperative course.
Delayed abdominal closure is not simply a technical choice. It often reflects the infant’s inability to tolerate compression after reduction of herniated organs, especially when the abdominal cavity is small and the respiratory reserve is limited. In that setting, the ability to anticipate the need for a staged approach could influence delivery planning, operative staffing, postoperative monitoring, and early family counseling. The study suggests that prenatal lung metrics may carry information about postoperative anatomy, not just postnatal survival.
The finding also narrows an important gap in CDH risk stratification. Liver herniation has long been treated as a strong severity marker, and it clearly mattered here as well. Yet O/E LHR remained informative after that adjustment, implying that lung underdevelopment contributes something distinct. Lung size may be capturing the degree of global fetal developmental constraint, not merely the presence of displaced liver. That broader developmental burden may be what ultimately predicts whether the abdominal wall can be closed without excessive pressure.
A Small Retrospective Cohort, but a Strong Signal
The study design carries the usual limits of a retrospective single-center analysis, and the sample size was modest. Those constraints matter because delayed closure is a multifactorial endpoint shaped by pulmonary status, abdominal domain, liver position, and operative judgment. A cohort of 45 infants cannot settle how this marker should be used across centers with different surgical thresholds or neonatal resuscitation practices.
The cohort was also restricted to isolated left-sided CDH, so the findings should not be extrapolated to right-sided defects or to cases with additional anomalies. External validation will need to show whether the 34.1% threshold survives in broader populations and whether its performance remains stable when applied prospectively. Without that testing, the result is best viewed as hypothesis-generating rather than ready for routine implementation.
Still, the signal is difficult to ignore. A prenatal lung metric that predicts not just the severity of respiratory disease but the likelihood of delayed abdominal closure points toward a more integrated model of fetal and neonatal risk. In CDH, the thorax and abdomen are linked from the start; this analysis suggests the same may be true for prediction.
The next step is external validation in larger, independent cohorts, ideally with prospective surgical decision-making and standardized definitions of closure strategy. Until then, the finding remains a promising statistical association rather than a bedside directive. Its value lies in clarifying which fetuses may arrive with both pulmonary compromise and a postoperative anatomy that will not accept immediate closure without tension.