Prevalence of polyhydramnios at a Danish hospital - a population-based study

Background. The purpose of this study was to determine the incidence of polyhydramnios, the related maternal and perinatal morbidity, and to estimate the association between perinatal outcome and the degree of polyhydramnios in a Danish population. Methods. The study population consisted of 168 women with singleton pregnancies and polyhydramnios diagnosed by ultrasound as a largest two-diameter pocket of > 50 cm(2). Mild polyhydramnios defined as > 50 and 100 cm(2), and severe polyhydramnios defined as >= 100 cm(2). The background population consisted of 8,347 pregnant women from the same hospital. Outcome measures were compared using x 2 test or Fisher's exact test. Results. The incidence of polyhydramnios was 2%, with 66.7% of cases mild, and 33.3% were severe polyhydramnios. The study population had an increased risk of emergency (19 versus 10.5%, p < 0.001) and elective (11.3 versus 5.0%, p < 0.001) caesarean section, as well as perinatal death (1.2 versus 0.3%, p < 0.05) compared to the background population. In cases of severe polyhydramnios, there was an increased risk of caesarean section (44.6 versus 23.1%, pp < 0.005), birth weight p > 4,000 g (28.6 versus 14.3%, pp < 0.05), and need for neonatal care (8.9 versus 0.9%, p < 0.01) compared to mild cases. Apgar score < 7, perinatal death and structural malformations only occurred in women with severe polyhydramnios. Conclusion. It is reasonable to distinguish between mild and severe polyhydramnios regarding special attention and follow-up, as caesarean section and perinatal morbidity and mortality are related to the degree of polyhydramnios. A two-diameter pocket >= 100 cm(2) could be used to separate mild from severe cases.