Risk of Genetic Abnormality in Fetuses With Unilateral Versus Bilateral Pleural Effusions.

Objective: Fetal pleural effusions are often associated with underlying genetic etiologies; however, data describing the incidence of genetic abnormalities are limited. We evaluated the rate of genetic abnormalities in pregnancies affected by primary unilateral and bilateral fetal pleural effusion.

Methods: This study is a retrospective cohort study of all patients evaluated at our center with a prenatal diagnosis of primary fetal pleural effusion from 2010 to 2022. All patients with a singleton pregnancy and diagnostic genetic testing were included. Patients were separated into two groups: those with unilateral or bilateral effusions at initial diagnosis. Genetic diagnoses, fetal interventions, and pregnancy outcomes were evaluated.

Results: Among 229 cases of fetal pleural effusion, 30 met the inclusion criteria. Unilateral effusion was seen in 14/30 cases (47%) and bilateral effusion in 16/30 cases (53%). Genetic abnormalities were present in 7/14 (50%) unilateral and 2/14 (14%) bilateral effusions (p = 0.046). Cases of bilateral effusion had higher rates of fetal intervention with thoracoamniotic shunt (69% vs. 14%; p = 0.004) and earlier delivery (33 vs. 36 weeks, p = 0.002). Bilateral effusions were found to have higher rates of respiratory distress syndrome and neonatal death (p = 0.03 and 0.04), respectively.

Conclusion: Pregnancies affected by primary fetal pleural effusion have a high rate of genetic abnormalities. Although bilateral fetal pleural effusions have worse perinatal outcomes, unilateral fetal pleural effusions have a high rate of genetic diagnosis and both unilateral and bilateral fetal pleural effusions warrant comprehensive prenatal genetic testing.