In placenta accreta, the placenta invades the myometrium so it doesn't easily separate from the uterus.

当发生胎盘植入时，胎盘组织将侵袭到子宫肌层组织，因此不易从子宫壁上脱离。

Placenta accreta or simply too much traction on the umbilical cord can both cause the placenta to be retained.

胎盘植入或过度的脐带牵引都能造成胎盘组织的残留。

Placenta previa is also associated with placenta accreta, which is where the placenta invades the myometrium and becomes inseparable from the uterine wall.

前置胎盘有时伴有胎盘增生，即胎盘侵入性生长进子宫肌层，无法与子宫壁分离。