A retained placenta can also happen when a womb stops contracting, or doesn't contract enough, to separate the placenta from the wall of the womb (a condition called uterine atony).
It is frequently associated with the conditions atonic seizure, atonic colon, uterine atony, gastrointestinal atony (occurs postoperatively) and choreatic atonia.
Resistance to urine flow requires the bladder to work harder during voiding, possibly leading to progressive hypertrophy, instability, or weakness (atony) of the bladder muscle.
