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.