What is one of the primary actions of oxytocin in childbirth?

Oxytocin plays a crucial role in childbirth, primarily by facilitating milk let-down. This hormone is released in response to various stimuli, such as the baby suckling at the breast. Oxytocin causes the myoepithelial cells around the alveoli in the breast to contract, which helps to eject milk into the ducts and towards the nipple, thereby allowing the baby to feed effectively.

In the context of childbirth, while oxytocin is known to be involved in stimulating uterine contractions during labor, its immediate action post-delivery is vital for initiating breastfeeding and promoting maternal bonding. This physiological response underscores the importance of oxytocin not only in labor but also in postpartum care by supporting successful breastfeeding.

The other choices do not encompass the primary actions of oxytocin during childbirth, as oxytocin's primary role in this context is more directly related to milk let-down and facilitating the breastfeeding process, rather than influencing fetal movement, decreasing uterine contractions, or increasing heart rate.