Why You’re Leaking Breast Milk: Myths & Common Causes

Have you ever woken up in the middle of the night to wet spots on your shirt or sheets from leaking breast milk?

You may be frustrated, confused or embarrassed about why your body is leaking milk – especially if you haven’t given birth yet or are not even pregnant. But you're not alone! 

Leaking breast milk can be caused by a number of changes to your body during pregnancy and nursing and even by a number of other things like your hormone levels or emotional triggers

Is the old wives' tale that hearing a crying baby can make breast milk leak actually true? 

Read on to learn common causes of leaking breast milk and how you can manage it. 

What causes breast milk to leak? 

During pregnancy, your body is constantly changing to support your growing baby both before and after their born! From the start of pregnancy, your body sends signals to start growing your breast’s secretory tissue, so you will have enough milk-producing breast tissue by the time your baby is born. 

Changes in your breast tissue during pregnancy 

Bud-like glands in the breast begin to grow and expand to create milk ducts and sacs called alveoli that will hold your breast milk. During this part of pregnancy, you may feel a soreness or tingling sensation in your breasts. 

These changes can trigger your nipples to leak milk in your nipples both before and after your baby is born. During the second and third trimester of pregnancy, it is common for breasts to begin producing colostrum. Colostrum is the first type of milk your body produces for early breastfeeding. 

Colostrum is commonly a yellow or gold color and can be thicker than typical breastmilk. Colostrum is packed with nutrients and antibodies, which are helpful in stabilizing your baby’s blood sugar levels and boosting baby’s immune system after birth and in the first few days of life.

Your breasts are engorged 

In the first few days after the baby is born, as colostrum transitions to normal breastmilk production, many people experience breast engorgement. Engorgement occurs when the breasts fill with more milk than the baby is removing. 

Engorgement is most common in the early days after the baby is born but can occur at other times as well. Having an oversupply of breast milk (a higher amount of milk than your baby needs) can also lead to more engorgement. 

Engorgement results in enlarged, firm and tender breasts that can feel warm to the touch and sometimes may appear reddened. During periods of engorgement, it is common for the breasts to leak milk.

Engorgement may also be more common when you are weaning the baby. Your body will adapt to how much milk the baby needs over time. 

If you suddenly cut feedings that your body has anticipated the baby will need, the milk will accumulate in your breasts and result in engorgement. In addition to being uncomfortable, engorgement may increase the risk of mastitis. 

Mastitis is an infection in the breast that can cause breast pain and redness, fevers, pain and body aches. Many cases of mastitis need to be treated with antibiotics. Ideally, it is best to wean gradually over time to help prevent this painful condition.

Do your baby's cries cause your breast milk to leak?

Some people who are lactating notice that they leak milk when they hear a baby cry. This may happen in response to their own baby’s cry, or it can happen randomly, such as hearing a baby cry in a busy store. 

This occurs due to a normal response called the letdown reflex, also known as the milk ejection reflex. Because babies have limited methods of communication, it is common for the baby to begin to cry when they are hungry. 

When your body becomes familiar with this signal of hunger from the baby happening before a breastfeeding session, you can begin to associate the two - a crying baby must mean that milk is needed!

How breastfeeding hormones produce milk 

There are two hormones that are most important for breastfeeding – prolactin and oxytocin. The milk ejection reflex is triggered by the hormone oxytocin. Oxytocin causes the milk that is already in the milk ducts of the breast to begin to flow toward the nipple. 

This helps the baby remove milk from the breast more easily. If the letdown reflex is triggered when the baby is not at the breast, it can cause the nipples to leak milk.

Many other things can stimulate the letdown reflex as well like touching or smelling your baby, or even just thinking about your baby! 

Effects of anxiety and stress on breastfeeding 

On the flip side, being in a lot of pain or experiencing stress or anxiety can interfere with the letdown reflex and make it harder to breastfeed the baby. 

It is important to foster an environment of relaxation and comfort when bonding with the baby and breastfeeding, as this can help establish the right hormones for breastfeeding. 

Tips to boost your milk supply when breastfeeding 

Doing skin-to-skin with the baby after the birth and working with a lactation consultant in the hospital and after discharge home are two things you can do to try to help establish and promote your supply in the early weeks of breastfeeding. 

When you are at home, having a comfortable routine to breastfeed the baby and relying on your partner or other support people to help get you snacks and water can decrease stress and promote breastmilk production and successful breastfeeding.

Can your breasts leak milk if you’re not pregnant?

Surprisingly, it is possible to produce breast milk even when you’re not pregnant and have never been pregnant!

If your breasts are leaking milk and you are not pregnant and have not breastfed within the past year or so, it’s time to call your healthcare provider. Producing milk to feed a baby is known as lactation while leaking milk unrelated to pregnancy or breastfeeding is called galactorrhea. 

Many different conditions can cause galactorrhea or discharge to leak from one or both nipples. Disorders of the breast, the thyroid or the brain can contribute to milk leakage or nipple discharge unrelated to birth. 

This could be something benign or something serious, but there is no good way to know without getting evaluated by a trusted healthcare provider. Your healthcare provider may recommend lab work, imaging or a combination of tests to determine the cause of your galactorrhea.

What to do about leaking breast milk?

While leaking breast milk may be annoying and result in some extra laundry, it can be a good sign that breastfeeding is working well and that you have a good supply of milk to feed your baby. 

If your breasts leak during pregnancy, it is a sign that your body is getting the processes in place to make milk for the baby after the birth. There are many different ways to deal with leaking breast milk. 

Breast pads 

Many people choose to use breast pads, which are either disposable or washable absorbent pads that can be placed inside a bra to absorb small amounts of leaking milk. If you use breast pads or nursing pads, it is important to change them frequently to keep the nipples as dry as possible. When the moisture of the milk is kept in constant contact with the nipple, it can increase the risk of thrush.

Breast shells 

Another option to deal with leaking breasts is to use breast shells. Breast shells are typically made of plastic or silicone and slide inside a bra to collect the extra milk so that it can be saved and fed to the baby at a later time.

It can be strange and messy when your breasts are leaking, especially if you feel like it's happening more often than "normal." But leaks are totally common side effects of pregnancy and breastfeeding. 

Learning how to pump and feed your baby on the best schedule for the two of you will help prevent any accidents and make sure you’re both happy and well-rested! 

For more information on pumping and storing your milk check out: Breastmilk Storage: How Long is Breast Milk Good For?