How your breasts will change during pregnancy and nursing

When most women think of their breasts during pregnancy, the following comes to mind: they grow (and grow and grow!). There's a lot going on with your breasts during these months while they're getting ready for breastfeeding.

Learning about your breast anatomy and physiology will help you understand the changes that will take place during and after pregnancy. It'll help you better understand breastfeeding and how your breasts prepare, adapt and aid your baby feed efficiently.

How your breasts will change during pregnancy

Breast Growth
Your breasts will start to grow as early as weeks after you become pregnant and might continue to get larger throughout your pregnancy, typically going up one or two cup sizes. Some women aren't aware of a change in size, while others can go up several few cup sizes; each experience is unique. The growth is caused by the milk-producing cells in the breast that are multiplying to prepare the breast for its upcoming job. (For more information on how your breasts will change in size, check out our Simple Guide to Nursing Bra Sizing)

Sore Breasts
Breast and nipple tenderness is often the first sign of pregnancy. Sometimes compared to the swollen, sensitive breasts you might have right before your period starts, the tenderness is caused by hormonal changes that increase blood flow and affect breast tissue. Usually the tenderness disappears after the first trimester.

Areolas
Your areolas become darker and might become bigger to help provide a sharper visual contrast for your newborn's eye.

Veining in the breast, bigger nipples, sensitive nipples
All of these changes are in preparation for nursing your baby.

Colostrum
During your last trimester, your breasts might begin to leak a small amount of colostrum, which is a thick, yellow substance. Colostrum is an "early" milk that your breasts begin to produce during the last few months of pregnancy. It's denser and lower in volume than regular breast milk but loaded with protein and antibodies. A little colostrum goes a long way in a newborn's tiny stomach. It's what your baby drinks from your breasts during her first few days of life, before your "mature" milk comes in at around Day 3 post-birth.

How your breasts will change after giving birth and while nursing

Estrogen and progesterone
During pregnancy, these hormones kept lactation at bay. They decrease immediately when the placenta comes out during childbirth.

Prolactin
When estrogen and progesterone levels drop after birth, prolactin kicks in. Called "the mothering hormone," it allows your breasts to begin making milk on an ongoing basis.

Oxytocin
This hormone is the workhorse and has a starring role in both the birth process and breastfeeding. It makes muscles contract and is responsible for creating contractions during labour. But oxytocin's job doesn't stop after birth. Nipple stimulation (such as your baby latching on) creates an oxytocin rush as well, which not only causes continued uterine contractions for a few days after birth (that's a good thing because it helps shrink your uterus back to size) but also causes the muscles surrounding the milk-producing cells in the breast to contract, squeezing milk into the ducts. This process is called "let down."

Let-down
Breasts have the ability to help feed your baby so she doesn't have to work so hard throughout the whole feeding to get the milk from your breast. When you're having a let-down, the milk is being squeezed into the ducts by contracting muscles and results in an increased flow of milk, making it easier for your baby to access it. You can have several let-downs during a single feeding, some you'll feel (a tingling, prickling sensation) and others you won't notice. Many women don't feel the let-down in the early months with their first baby but might be more aware of it later in lactation or with their second baby. And yes, let-downs can happen when you're not breastfeeding too. Sometimes just the sight or thought of your baby can trigger milk flow. Thank goodness for breast pads!

Milk ducts
Each breast has ductal structures, which are the holding tanks for your milk. When you have let-down, the milk goes through these ducts and comes together into anywhere from 9 to 15 nipple pores per breast. This is important to visualize because it results in the milk flowing from your breast like water from a showerhead, and not like a bottle nipple with only one hole. That's why a good, deep latch is essential for your baby to access as much milk as possible.

Engorgement
Your sore, swollen breasts have come back, but take heart—this phase only lasts for a few days. About 2 or 3 days after you give birth, your mature milk comes in. This process increases the blood flow to your breasts, and the surrounding tissue starts to swell. While not every new mom experiences this the same way, many women's breasts become quite large and hard and sore. The solution? Breastfeed! Your breasts will soon adapt to your baby's needs and produce the right amount of milk, plus they'll become softer and less painful. And if after breastfeeding your baby has taken some of the milk but doesn't drain your breasts completely, you might want to remove some of the additional milk with a breast pump to get some relief. See our section on engorged breasts for more detailed solutions.

As you can see, your breasts will go through a lot of changes in addition to growth during pregnancy and nursing. Their ability to adapt and feed your baby is really quite wonderful.

If you're experiencing ongoing pain in your breasts, there are several possible causes, including plugged ducts, engorgement and mastitis. Each one can be solved in different ways. However, painful nipples and breasts can often be helped by adjusting your baby's latch. If you ever have any concerns about the changes you're experiencing, talk to your health care professional.

Tips for success

  • Not all women have the same changes or sensations in their breasts. Each experience is unique.
  • Always call your health care professional if you have concerns about these changes, or if you have ongoing or extreme pain in your nipples or breasts.

Source: Heather Kelly is an International Board Certified Lactation Consultant (IBCLC) who also sits on the Bravado Breastfeeding Information Council Heather has been practicing in New York City since 2001.

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Heather Kelly
Heather is an International Board Certified Lactation Consultant.
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