RESUMEN
OBJECTIVE: To evaluate the association between orexin-A level and idiopathic polyhydramnios. DESIGN: Case-control study. SETTING: Tertiary-level university hospital. POPULATION: Ten term pregnant women with idiopathic polyhydramnios and, as the control group, 20 pregnant women with normal amniotic fluid levels. METHODS: Amniotic fluid level was measured at admission for delivery using enzyme-linked immunosorbent assay. Maternal blood was obtained from a cannulated vein immediately before delivery, and umbilical blood was collected at the time of delivery, before the separation of the placenta. MAIN OUTCOME MEASURES: Maternal and umbilical levels of orexin-A. RESULTS: Mean umbilical serum orexin-A level was significantly lower than maternal serum orexin-A level. Umbilical serum orexin-A level was positively correlated with maternal serum orexin-A level, but negatively correlated with amniotic fluid index and birthweight. Umbilical serum orexin-A level was lower in the idiopathic polyhydramnios group than in the control group. However, no difference in maternal serum orexin-A level was observed between the two groups. CONCLUSIONS: Idiopathic polyhydramnios was associated with decreased umbilical serum orexin-A levels. Our results provide evidence that orexin-A expression may be involved in amniotic fluid regulation, causing polyhydramnios by downregulation.