The maternal layer, the decidua basalis, is literally a flattened out bag of blood with uterine arteries delivering blood in and uterine veins pulling blood out.
所谓“母体层”,即基蜕膜,就是一个平整的血袋,将子宫动脉的血输送进去。
英语百科
Uterine veins
The uterine veins are tributaries of the internal iliac veins. They are found in the cardinal ligaments.