The two main hormones involved in lactation are prolactin and oxytocin. When your baby nurses, signals are sent from your breast to your brain which creates these. If any of these hormonal roles fail, there may not be enough milk. Contraceptives which contain estrogen have been linked to reduced milk supply. Menstruation can affect your milk supply, especially during the end of the cycle due to a decrease in prolactin. Nursing may be uncomfortable, and you might see your baby nursing more freque