Your Guide to Prolactin and Breastfeeding

Prolactin is one of several hormones (including oxytocin, estrogen, and progesterone) that play a significant role in pregnancy and breastfeeding. Prolactin is made in the pituitary gland of the brain. Although it performs many functions in the human body, it is known as a breastfeeding hormone because of its key function in the production of breast milk.

While prolactin is always present in the body, its levels rise significantly during pregnancy, at the time of birth, and while breastfeeding, affecting breast milk production as well as menstruation and fertility.

What Is Prolactin?

While it's named for its primary role in lactation, prolactin also plays important roles in the reproduction system, including impacting the production of sex hormones (including testosterone), behavior, and the immune system in both females and males. If you produce too much or too little prolactin, these systems can be adversely affected, which can impact, among other things, menstruation and fertility (in people of any gender).

Prolactin and Lactation

Prolactin acts on the body in a variety of crucial ways from pregnancy through breastfeeding.

Pregnancy

During pregnancy, prolactin prepares your breasts to begin breast milk production. However, the high levels of estrogen and progesterone produced by the placenta, prevent the prolactin from making a large amount of mature breast milk.

Childbirth

When you deliver your baby, and the placenta leaves your body, estrogen and progesterone levels go down and prolactin levels go way go up, signaling the milk-making glands in your breasts to make breast milk.

The First Days Postpartum

The postnatal rise in prolactin is what gets milk production started, but it's not enough to maintain the production of breast milk. To keep making breast milk, you need to breastfeed your baby or pump your breast milk often.

When your baby breastfeeds, or you pump your breast milk, the nerves in your breasts send a signal to your brain to release the hormones oxytocin and prolactin. The prolactin tells the milk glands in your breasts to make more breast milk, and the oxytocin is responsible for getting the breast milk from your breasts to your baby. As long as you continue to breastfeed (or pump) very often, your body will continue to release prolactin, and you will continue to make milk.

If You Don't Breastfeed

The levels of prolactin in your body are high during pregnancy and right after the birth of your baby. But since your body releases prolactin in response to stimulation at your breasts, if you do not breastfeed or pump your breast milk, your levels of prolactin will begin to go down.

In the first few weeks postpartum, you will still produce breast milk and may experience breast engorgement even if you decide that you don't want to breastfeed or pump. But, in the absence of breastfeeding or pumping, the production of breast milk will slow down and eventually stop.

Prolactin and Breast Milk Supply

As noted above, a healthy level of prolactin is important in order to maintain your breast milk supply. By the same token, dips in prolactin levels can result in reduced milk supply.

Causes of Decreased Prolactin

Many things can affect the level of prolactin in your body. Causes of lower than optimal prolactin levels for nursing mothers include:

• Birth control that contains estrogen: When there's a change in the balance of estrogen and prolactin, it can affect the breast milk supply. Birth control that contains estrogen is known to cause a decrease in milk production.
• Breast surgery: Breast surgery performed near the areola or the nipple can cause damage to the nerves that signal the brain to release prolactin.
• Depression: Prolactin levels are lower in mothers who suffer from depression. 
• Early pacifier use: The use of a pacifier in the early weeks of breastfeeding reduces some of the breast stimulation that you would be getting if you put your baby to the breast instead. The more you breastfeed, the more prolactin you will produce. When your child uses a pacifier, it's a lost opportunity to increase prolactin and support a healthy supply of breast milk.
• Numbing creams: A numbing cream should never be used to treat sore nipples. Not only can it numb the baby's mouth, but it can numb the nerves in the breast, as well. If the nerves cannot send a signal to the brain, prolactin will not be released.
• Obesity: Being overweight (or significantly underweight) can reduce your prolactin levels.
• Smoking: Smoking could lead to a decrease in the levels of prolactin.
• Supplementing: If you supplement your baby with formula or give the baby water between feedings, you aren't signaling your body to release as much prolactin.

Ways to Increase Prolactin Levels

The best way to raise your prolactin levels is to breastfeed or pump very frequently. When your baby is born, you should be breastfeeding or pumping at least every two to three hours around the clock. The more often you stimulate your breasts, the more your brain will release prolactin. There are also certain herbs, foods, and medications that you can try to help boost your prolactin levels.

However, it's important to point out that raising prolactin levels alone are not enough to create a healthy supply of breast milk. The stimulation of the breasts and the removal of breast milk from the breasts are just as important.

Prolactin and Menstruation

When you're breastfeeding, prolactin levels are high, and estrogen levels are low. The relationship between these hormones keeps your breast milk supply up and your period away. If you breastfeed exclusively, it can delay the return of your period for many months.

If you do not breastfeed, or if you combine breastfeeding and formula feeding, these hormone levels will change, with prolactin decreasing and estrogen increasing. So, in the absence of exclusive breastfeeding, you could see the return of your period as early as six weeks after the birth of your baby.

When your period does return, more estrogen and less prolactin can affect the production of breast milk. Sometimes, it's just a dip in your supply during your period. But, it's possible that once your period returns, your breast milk supply will remain low. However, you can take measures to boost your supply, such as nursing or pumping more often.

Prolactin and Fertility

Exclusive breastfeeding is associated with high levels of prolactin. These high levels of prolactin prevent your ovaries from ovulating or releasing eggs. So, if you breastfeed exclusively without giving your baby any supplements for the first six months after the birth of your baby, it is very unlikely that you will ovulate or become pregnant. The lactational amenorrhea method of birth control (LAM) is based on high prolactin.

However, as noted above, once you are no longer breastfeeding exclusively, your prolactin levels will start to go down. Then, your fertility will begin to return, and you will be more likely to become pregnant again if you're sexually active.

Likewise, prolactin can interfere with your ability to become pregnant again if you're still breastfeeding or you've weaned your baby but you're still producing breast milk, especially if you have not yet seen the return of your period. So, if you're ready to get pregnant again, but you're having trouble conceiving, talk to your doctor. Your doctor may order a blood test to check your prolactin level.