AQP9 and oligohydramnios: Our results showed that the expression of AQP1 and AQP9 was dramatically decreased in both placental trophoblasts and amnion epithelial cells in oligohydramnios, which suggested that downregulation of AQP1 and AQP9 is an adaptive response to isolated oligohydramnios, which leads to a reduction in intramembranous absorption, maintaining AF homeostasis.