Prognostic value of the nutmeg lung pattern/lymphangiectasia on fetal magnetic resonance imaging

Background: A nutmeg lung pattern on magnetic resonance imaging (MRI) is an imaging finding associated with pulmonary lymphangiectasia. However, the prognostic value of the nutmeg lung pattern is unknown.

Objective: To evaluate the clinical associations of nutmeg lung indicating lymphangiectasia on fetal lung MRI and its relationship with early mortality in fetuses with primary and secondary lymphangiectasia.

Materials and methods: We retrospectively identified all pregnant patients with a fetal MRI performed for indication of evaluating for pulmonary lymphangiectasia from 2006 to 2019. Two readers evaluated the fetal MRIs and interobserver agreement was calculated. Multivariable logistic regression models were performed to estimate the association of the echocardiographic findings and the presence of nutmeg lung. Kaplan-Meier and Cox regression analyses were performed to evaluate association with mortality in the first 30 days of life. Survival analysis was defined as mortality or orthotopic heart transplant at 30 days of age. P<0.05 was considered significant.

Results: Our sample included 53 fetuses. Forty-seven (89%) had congenital heart disease (CHD) and 6 (11%) were diagnosed postnatally with primary lymphangiectasia. Interobserver agreement was 0.83. Pulmonary vein congestion on echocardiography was the strongest predictor of nutmeg lung (odds ratio [OR]=12.0, P=0.002). Ten fetuses reached the outcome of heart transplantation (n=1) or death (n=9) within the first 30 days of life. In fetuses with CHD, survival of those with nutmeg lung was significantly lower than in those without (P<0.001). Nutmeg lung was an independent risk factor for 30-day mortality (hazard ratio [HR]: 6.1, P=0.01).

Conclusion: Nutmeg lung pattern on fetal MRI is an independent risk factor associated with 30-day mortality in fetuses with CHD.