Uterine atony can also occur when the uterine muscles fatigue during the delivery process because of prolonged labor.
宫缩乏力还可以发生于由分娩过程中产程延长引起的子宫肌肉疲劳时。
英语百科
Prolonged labour
Prolonged labour is when the total duration of childbirth is greater than 24 hours. There are two main types, one when the latent phase of labour is greater than 8 hours and the other when the active phase of labour is greater than 12 hours.
The cause can be due to: poor uterine contractions, the baby's position or size being abnormal, or issues with the pelvis or birth canal. The last two may result in obstructed labour.