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.