Decreased umbilical orexin-A level is associated with idiopathic polyhydramnios.

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.