This is the main hormone involved in the formation and production of milk. It is secreted by the anterior pituitary (the part of the brain that regulates hormones) and the release is prompted by delivery of the placenta. Prolactin levels rise during pregnancy and drop for a short period just before birth, then they rise once again a few hours after delivery, or immediately when the baby is put to the breast. The levels should be approximately 150 to 200 ng/ml at term; they double during a breastfeeding session. Prolactin levels during lactation slowly drop over time after birth until the baby is weaned. (The standard range for a non-pregnant woman is 2.8 to 29.2 ng/ml. It is recommended that, for optimal health, women maintain prolactin levels no higher than 7.3 ng/ml).
If a mother does not breastfeed, prolactin levels typically return to non-pregnant levels by seven days postpartum. For this reason, it is always recommended to breastfeed more than eight times in a 24-hour period in order to avoid the decline of the concentration of prolactin before the next feeding. In addition, stimulating both breasts at the same time increases prolactin levels by about 30%.
Prolactin levels are not dependent upon the rate of milk formation or milk yield after lactation is established. They are also not related to the degree of postpartum engorgement. However, prolactin levels may be affected by smoking and beer -- moms who smoke cigarettes have a lower level and those who drink beer may have higher levels.
Source:
Riordan J, Auerbach KG. Breastfeeding and Human Lactation. Jones and Bartlett. 2nd Edition.
