Of 2081 high-risk pregnancy patients who underwent antepartum fetal surveillance tests, 72 (3.5%) patients demonstrated evidence of polyhydramnios using the amniotic fluid index to assess the amniotic fluid volume. In these patients, an increased incidence of fetal macrosomia, premature births, non-reactive nonstress tests, perinatal morbidity, and fetal anomalies was observed. These data suggest that if polyhydramnios is encountered during an ultrasound evaluation, consideration should be given to the possibility of latent or uncontrolled diabetes mellitus or fetal macrosomia or anomaly; fetal surveillance and genetic evaluation also should be considered.