Long-term outcome of cases of fetal pleural effusion: A study at a single perinatal center in Japan

Purpose: To analyze the long-term prognosis of primary and secondary fetal pleural effusion (FPE). Methods: We investigated all cases of FPE in a single University hospital (2005–2020). Cases were classified as primary (cases with only pleural effusion) and secondary (cases with other abnormalities such as chromosomal abnormalities or fetal cardiac failure). We retrospectively reviewed the medical records from the time of diagnosis, to assess medical procedures performed, chromosomal test results, and clinical outcomes. Results: Among 18 027 deliveries, 17 FPEs were identified (primary FPE: 8, secondary FPE: 9). Most primary FPEs were diagnosed in the second trimester of pregnancy, while all secondary FPEs were diagnosed in the third trimester. Secondary FPE was often associated with chromosomal abnormalities, including trisomy 21. The prognosis of pleural effusion caused by trisomy 21 was relatively good, except for cases with TAM. Cases of secondary FPE without trisomy 21 were of cardiac origin, and the neonatal prognosis was poor. The short-term prognosis was better in the primary FPE group, but long-term follow-up identified conditions such as acute encephalitis with refractory, repetitive partial seizures, developmental delay and attention deficit hyperactivity disorder. Conclusion: Fetal pleural effusion without the presence of chromosomal abnormalities or morphologies has a good short-term prognosis, but the long-term prognosis is poor. Thus, long-term follow-up is necessary for all cases of fetal pleural effusion.