Opium-derived analgesic that is used through several ways of administration (epidural, intravenous, mouth, skin). It is excreted into breast milk in non-significant amount without observed problems among infants from treated mothers. Plasma levels of those infants were undetectable. It has been authorized for treatment of small infants and neonates. After a mother has underwent anesthesia by the use of Fentanyl, she may breastfeed her baby as soon as her recovery and general conditions may permit it. Fentanyl stimulates secretion of Prolactin, however, after Lactation has been established, Prolactin level has a poor relationship with production of mother's milk. There is controversy about the effect of analgesic medication used for labor management (Epidural anesthesia with Fentanyl added or not ) on the initiation of breastfeeding, both on starting of phase II of Lactogenesis or the infant ability for suckling. Some studies have pointed out to a higher risk for a delay in the initiation of Lactogenesis II (milk coming in) for longer than 3 days after birth, even though it would not affect the weight loss of the newborn. Other studies have found a higher risk for a delay in the first latch-on at the breast, higher body temperature and irritability or somnolence. Some others however, failed to show the same findings. It appears to be of more paramount importance the women's support for the establishment and continuation of breastfeeding, than the negative effect that would be exerted by administration of analgesia or anesthesia during labor. Fentany has lesser effect than Pethidine (Demerol) on initiation of breastfeeding. It occurs a higher milk production and weight increase of the infant if there is an adequate pharmacological control of the pain that appears after vaginal birth or C-section. The American Academy of Pediatrics - says that is usually compatible with breastfeeding.