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Purpose: To determine the interobserver variability of prenatal magnetic resonance (MR) lung volumetry and to assess the value of MR lung volumetric findings as predictors of outcome in fetuses with congenital diaphragmatic hernia., Materials and Methods: Prenatal MR imaging was performed in 26 fetuses with unilateral congenital diaphragmatic hernia. Two independent observers performed planimetric measurement of lung volume. Relative lung volume was calculated as the observed total lung volume expressed as a percentage of the total lung volume predicted from fetal size. Relative lung volume was correlated with the ultrasonographic lung-head ratio in left-sided congenital diaphragmatic hernias evaluated before 27 weeks gestation (n = 21) and with pregnancy outcome in all cases of isolated left-sided congenital diaphragmatic hernia without prenatal intervention (n = 11)., Results: Observers demonstrated excellent agreement in total lung volume measurements at MR imaging, with an intraclass correlation coefficient of 0.95. Relative lung volume was positively correlated with lung-head ratio (r = 0.78, P <.001). By using rank order analysis in the pregnancy outcome group, relative lung volume was predictive of prognosis (P <.05) when adjusted for gestational age at delivery and birth weight. Three of four fetuses with a relative lung volume of less than 40% died., Conclusion: Interobserver agreement is high at MR lung volumetry, and its findings are predictive of outcome in fetuses with isolated left-sided congenital diaphragmatic hernia.

Purpose: To determine which parameters are most closely correlated with normal fetal total lung volume and to investigate the use of these parameters in the evaluation of fetal pulmonary hypoplasia., Materials and Methods: Single-shot rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging was used to perform planimetric measurement of total lung volume in 46 fetuses at 18-32 weeks gestation. Total lung volume was correlated with gestational age, and biometric parameters in fetuses were correlated with normal chest findings at ultrasonography (US) (n = 24). This analysis was used to evaluate relative lung volume in fetuses suspected of having pulmonary hypoplasia (n = 22)., Results: Normal fetal total lung volume was strongly correlated with liver volume measured at MR imaging (r = 0.94), fetal weight estimated at US (r = 0.93), head circumference measured at US (r = 0.90), and gestational age (r = 0.87). In fetuses suspected of having pulmonary hypoplasia, the relative lung volume varied from 4.6% to 81.6% when the observed total lung volume was expressed as a percentage of the predicted total lung volume., Conclusion: Normal fetal total lung volume is strongly correlated with biometric measurements. Relative fetal lung volume can be calculated by expressing the observed volume as a percentage of the predicted volume calculated from biometric measurements; knowledge of the relative fetal lung volume assists in the confirmation and quantification of fetal pulmonary hypoplasia.