Breast changes during pregnancy occur very early on in pregnancy. In fact, it can often be the first sign that you are pregnant.

As your body undergoes changes during pregnancy, so do changes occur in your breasts during the successive trimesters of pregnancy. Post-delivery, it is the breasts that help the mother satisfy her most important obligation to her baby, that of feeding it.

For lactation to occur, the breasts undergo certain changes, anatomically and physiologically during and after pregnancy.

Soon after conception, your hormone, estrogen, and progesterone levels change rapidly to facilitate pregnancy and lactation. Your breasts are one of the first areas where you can feel these changes.

You may experience breast changes in early pregnancy – in fact, it’s often the first sign you’re pregnant.

Your breasts and nipples become fuller, sensitive, and tender as early as three to four weeks after conception. These effects are the result of the surging hormones estrogen and progesterone.

Breast changes are often the first that women report upon finding out that they are pregnant. These changes of breast soreness and increased sensitivity may last throughout pregnancy.

However, certain changes may require immediate attention because they could be a signal of some pathology. These include breast pain accompanied by fever, nipple pain, or a persistent lump in the breast with dimpling of the skin over the breast, which could be a sign of breast cancer.

How do hormones influence breast changes and breastfeeding during pregnancy?

Estrogen, prolactin, and progesterone are the hormones that act in tandem to promote lactation.

  • Estrogen levels rise steadily during pregnancy and reach their peak in the third trimester. Estrogen stimulates the growth of glandular tissue and breast duct cells, which cause the breasts to enlarge. It also brings about the secretion of prolactin.
  • Progesterone levels are also very high during pregnancy. Progesterone encourages the growth of the milk-producing cells in the glands of the breasts.
  • Prolactin initiates and increases milk production and causes the breasts to enlarge. After delivery, the levels of estrogen and progesterone fall while the prolactin levels rise. Prolactin promotes the growth of mammary alveoli of the mammary gland, where the actual production of milk occurs. This brings about lactation. The first rise in serum prolactin levels is seen 30–40 days after conception. Prolactin levels continue to rise until delivery. After the baby is born, prolactin levels stay high only if you are breastfeeding. In women who do not breastfeed, prolactin levels return to normal soon after delivery.

Early pregnancy breast changes during the first trimester (weeks 1 to 12)

  • Breasts start to become swollen and tender
  • There may be tingling
  • The nipples may become erect more than usual
  • Changes in the color and size of the nipples
  • There may be tenderness and change in sensation of the nipple and breast
  • The Montgomery glands on the areola become more prominent

Changes during the second trimester (weeks 13 to 27)

  • In the second trimester of pregnancy, the breasts become larger and heavier. You may require a bra of a larger size to support your breasts.
  • The tenderness and tingling feeling will decrease.
  • The veins on the skin of the breasts become more noticeable
  • The nipples and the areolas become darker
  • Small bumps caused by the enlarged Montgomery glands appear.
  • Stretch marks may begin to appear on the skin of the breasts.
  • During the 5th month of pregnancy (16th to 19th week), small drops of clear or yellowish milky fluid leak from your nipples and may stain your bra. You can use a washable breast pad inside your bra. This yellowish fluid is called colostrum and this signals that your breasts are getting ready to produce milk and feed the newborn. Colostrum is, therefore called the “pre-milk”. It is very nutritious and protects the newborn against diseases during the first few days of breastfeeding. From about the 16th week of pregnancy, therefore, the breasts are able to produce milk.

Changes during the third trimester

In the third trimester, your breasts will grow more in size and may feel heavier as the milk-producing cells grow bigger. They may feel uncomfortable and sometimes may cause pain. You may need a larger well-fitting bra to support them to relieve the discomfort.

How big can the breasts grow during pregnancy? It differs from woman to woman but the breasts can increase one to two cups bigger than what they were before pregnancy. The ribcage too expands to make room for the growing fetus inside the abdomen.

If your breasts have not discharged colostrums earlier, they may do now in the third trimester. However, some women do not discharge colostrums at all, which does not affect their breastfeeding.

Changes in breasts after delivery of the baby

Breast changes continue to occur even after childbirth. The milk starts coming about 3 to 5 days after delivery of the baby. Till then, the newborn breastfeeds on colostrum produced by the breasts during the first 3 to 5 days post-delivery. Colostrum is nutritious and boosts the baby’s immunity, which helps fight infections.

After the first few days of making colostrum, the breasts become fuller and feel firmer – a sign that mature milk is increasing and replacing the colostrum.

Breast milk varies from woman to woman but mostly the milk is now whiter and creamier.

Other post-pregnancy changes include:

  • Tingling sensation. The breastfeeding woman may notice a tingling sensation in her breasts when the baby is feeding. This can indicate that the milk is being released into the ducts from the milk glands in order that the baby can drink it. This is called the “let-down” of milk. Over time, these sensations decrease.
  • Increased breast size. The breasts stay enlarged during the first few months of breastfeeding. After the baby has fed, the breasts become softer and less full. After the baby shifts to eating solid foods, the breasts shrink in size. After breastfeeding has been stopped, the breasts may return to their original size, may become smaller, or may stay slightly larger than before. This varies from woman to woman.
  • Sore or cracked nipples. Initially, during breastfeeding, some women may experience nipple pain. At times, the nipples may develop cracks and may bleed or blister. This happens due to incorrect latching of the baby onto the nipple or strong sucking. Nipple creams are available to ease this symptom.