Reliability of the lung-to-head ratio as a predictor of outcome in fetuses with isolated left congenital diaphragmatic hernia at gestation outside 24-26 weeks.

OBJECTIVE: The purpose of this study was to investigate the relationship between lung-to-head ratio (LHR) and gestational age (GA) in fetuses with isolated left congenital diaphragmatic hernia and to determine the applicability and reliability of LHR to predict postnatal outcome beyond 24-26 weeks of gestation. STUDY
DESIGN: The institutional review board approved this retrospective review of the University of California, San Francisco, Fetal Treatment Center database for cases with left congenital diaphragmatic hernia who were referred between March 1995 and June 2004. LHR was determined at the initial evaluation. One hundred seven live-born fetuses at 20-34 weeks of gestation (excluding cases that were lost to follow-up, with factors that potentially could influence the LHR measurement or postnatal outcome, or that were terminated electively).
RESULTS: The median GA at LHR measurement was 25.6 weeks; the median LHR was 1.01; the median GA at birth was 37.7 weeks; and the overall survival rate was 59% (64/107). The median LHR of nonsurvivors was significantly lower than that of survivors, but neither GA at LHR measurement nor at delivery was significantly different between the groups. Multiple logistic regression analysis confirmed LHR to be an independent predictor of postnatal survival, and receiver-operator characteristic curve analysis demonstrated that an LHR of > or = 0.97 has the highest performance in predicting postnatal survival. When fetuses were grouped by GA at initial LHR measurement to determine reliability of LHR, specifically with respect to GA, in the 26-34 and 24-26 weeks of gestation groups, median LHR of survivors was significantly higher than that of nonsurvivors, and receiver-operator characteristic curve analysis confirmed LHR to be a reliable predictor of postnatal survival. However, for fetuses at 20-24 weeks of gestation, there was a trend toward a higher LHR in survivors, although this did not reach statistical significance.
CONCLUSION: A significant positive linear relationship exists between LHR and GA at the time of measurement, such that LHR reliably predicts postnatal survival in fetuses with left congenital diaphragmatic hernia at 24-34 weeks of gestation and less reliable at 20-24 weeks. However, given the limitations of a retrospective, cross-sectional study, further prospective longitudinal studies that will investigate the change of LHR with GA and its association with fetal outcome are necessary.