What primarily causes after pains in postpartum women?

Afterpains in postpartum women are primarily caused by uterine contractions during the process of involution. After childbirth, the uterus contracts to reduce in size and return to its pre-pregnancy state. These contractions can lead to discomfort or pain, commonly referred to as afterpains.

The process of involution is crucial for several reasons, including the prevention of excessive postpartum bleeding by compressing the blood vessels and promoting the healing of the uterine lining. As the uterus contracts more forcefully, especially during breastfeeding when oxytocin is released, women may experience increased intensity of these afterpains.

While hormonal shifts and physiologic stress from the birth process can contribute to the overall experience of postpartum recovery, they do not directly lead to the specific sensations of pain associated with afterpains as uterine contractions do. Similarly, increased blood volume is a physiological characteristic during pregnancy and does not play a role in causing these painful contractions.