Repetitive MR measurements of lung volume in fetuses with congenital diaphragmatic hernia: individual development of pulmonary hypoplasia during pregnancy and calculation of weekly lung growth rates.

Objective: To investigate individual changes in fetal lung volume (FLV) in fetuses with isolated congenital diaphragmatic hernia (CDH) and to calculate weekly growth rates of the FLV using serial MR examinations during pregnancy.

Methods: MR-FLV was measured in 89 fetuses with CDH. All fetuses received two MRIs. A mean weekly growth rate of the FLV was determined for each fetus and compared with the growth rate of healthy fetuses.

Results: Mean observed-to-expected MR-FLV (o/e MR-FLV) measured at the first MRI was 33.3 ± 12.2% and 29.5 ± 10.9% at the second MRI. In 61% of all fetuses (54/89) the o/e MR-FLV decreased during pregnancy, 26% (23/89) showed an increase in the o/e MR-FLV and 13 % (12/89) had stable values. First and last o/e MR-FLV values were significantly associated with mortality and neonatal extracorporeal membrane oxygenation (ECMO) requirement with a higher prognostic accuracy of MR-FLV measurements near delivery. Patients with CDH had lower weekly lung growth rates than healthy fetuses. There was a significant difference in the mean weekly growth rate between survivors and non-survivors and patients with and without ECMO requirement.

Conclusion: Individual development of FLV in patients with CDH during pregnancy is extremely variable. Follow-up MR-FLV measurements are advisable before deciding upon pre- and postnatal therapeutic options.

Key Points: • Lung development in congenital diaphragmatic hernia (CDH) during pregnancy is extremely variable. • MRI demonstrates that lung growth rate is reduced in fetuses with CDH. • The final observed-to-expected fetal lung volume provides the best prognostic information. • Follow-up measurements are advisable before deciding upon therapeutic options.