PM1068: A Fetal Care Center Perspective on Polyhydramnios: Potential Causes, Pregnancy Outcomes, and Diagnostic Accuracy

Background: Polyhydramnios, affecting 1-2% of pregnancies, may result from maternal causes such as diabetes or alloimmunization, or fetal factors, such as decreased fetal swallowing, gastrointestinal obstruction, or increased fetal urine production. Nearly all publications on this topic result from review of ultrasound databases with limited analysis of pediatric outcomes. Furthermore, there are no studies that discuss the role that fetal MRI may play in evaluation of pregnancies complicated by polyhydramnios. The purpose of this study was to examine the causes of polyhydramnios and respective perinatal outcomes in a specialized population referred to a comprehensive fetal therapy program.

Methods: The medical records of all patients referred to Cleveland Clinic’s Fetal Care Center 2015-2021 were reviewed to identify all singleton pregnancies complicated by polyhydramnios. Polyhydramnios was classified by maximum amniotic fluid index (AFI) 25-29.9 cm or maximum vertical pocket >8 cm with normal AFI measurements, moderate (AFI 30-34.9) or severe (AFI ≥35). A REDCap® database was created. Etiologies, prenatal and postnatal imaging findings, and outcomes to 1-year of age were evaluated. Statistical analysis was performed using Fisher’s exact test, Student’s t-test, and ANOVA with p<.05 considered significant.

Results: 153 patients had polyhydramnios; 59 classified as mild, and 94 classified as moderate or severe (Table 1). Polyhydramnios resolved in 26% of cases overall, even in 15% of severe cases. Though there were no significant differences in gestational age at birth between groups, moderate and severe polyhydramnios were associated with higher rates of perinatal mortality, lower Apgar scores, and longer NICU stays. In this series, maternal diabetes alone was the cause of polyhydramnios in 16 cases (10.5%) including 7 (11.9%) cases with severe polyhydramnios. Polyhydramnios was considered idiopathic in 37 cases (24%) in this series as no cause was identified either pre- or postnatally. An anatomic cause was significantly more common in those with moderate or severe polyhydramnios compared to those with mild polyhydramnios (34.3% and 32.2% vs. 5.1%, p<.001). The anatomic cause of polyhydramnios was diagnosed prenatally in 30/34 (88.2%) cases. All 4 cases in which the anatomic cause was not diagnosed prenatally (CHAOS with tracheoesophageal fistula; esophageal atresia; duodenal atresia; anorectal malformation) had moderate or severe polyhydramnios; 2 had fetal MRI.

Conclusion: The severity of polyhydramnios is associated with worse pregnancy outcomes including higher rate of perinatal demise, lower Apgar scores and longer NICU stays. For mothers referred to a comprehensive fetal therapy program, polyhydramnios tends to be more moderate or severe, and is associated with a higher rate of congenital anatomic abnormalities and lower rate of idiopathic cases when compared to average patient populations. Fetal MRI may be considered for pregnancies complicated by polyhydramnios, particularly moderate or severe forms, for which no cause is apparent by prenatal sonography or maternal testing alone.