In patients with oligohydramnios, AQP9 expression was positively associated with AQP1 expression in both placental trophoblasts (Table 8, P < 0.05, r = 0.640) and foetal membranes (amnion epithelial cells and chorion cytotrophoblasts) (Table 9, P < 0.05, r = 0.634). The gene discussed is AQP9; the disease is oligohydramnios.