Breast and Nipple Changes During Pregnancy

Changes to the breast are common during pregnancy and such changes are often an early sign that a woman is pregnant. Examples include tenderness of the breast and nipple and an increase in breast size that makes the breasts feel heavy.

Breast tissue is also present in the armpit and some women find the tissue under their arms also increases in size. Tingling and soreness in the breasts is also common, especially in the nipples. This occurs as a result of an increased progesterone level and milk duct development.

Visual Changes in the Breasts

As a pregnancy progresses, the nipples and skin that surrounds them (areola) become darker in color as a result of hormones that affect skin pigmentation.

Veins in the breast may also become more prominent as the blood supply to the breast is increased. This is due to the fact that a woman’s overall blood volume is increased to aid the baby’s development.

Changes to the nipple and areola include the development of glands on the areola called Montgomery tubercles. These glands are sebaceous glands that become raised, bumpy and more obvious to the eye. Their function is lubricate during breastfeeding, thus protecting the nipples from irritation, and also to keep germs away from milk before being ingested by the baby.

In some cases, these glands can become infected. Medical attention should be sought if redness, swelling or pain is experienced around the nipple.

Stretch marks can also develop due to the increasing size of the breasts during pregnancy.


Due to the increase in estrogen production, the hormone prolactin is produced. This hormone encourages enlargement of the breasts and milk production. Milk-producing glands are grown with the help of progesterone, another hormone that is produced in greater amounts during pregnancy.

From around the 16th week of pregnancy, the breasts start to produce milk and the nipples may start to leak small amounts of a fluid called colostrum, which is also referred to as the “first milk.” At first, this fluid is yellowish in color, but after birth, it becomes pale and virtually colorless. Overstimulating the nipple while during these period carries risks of premature labor.

This milk is rich in the nutrients and antibodies that the baby requires to protect it during the first few days after birth. Occasionally, blood may also leak from the nipple, which can happen as a result of blood vessels suddenly growing and increasing in number.

During the last weeks of pregnancy, the nipples continue to increase in size, as does the breast, while the cells that produce milk become larger.

Breast Lumps

Sometimes, lumps develop in the breast during pregnancy. Usually these are cysts that are either filled with fluid or milk. Fibroadeonomas, which form in the breast lobules (a gland that produces milk) are also common. These lumps are not cancerous, and almost all lumps that develop during pregnancy are benign.


An increase in breast size as they grow during pregnancy can cause discomfort and pain, which may be eased by wearing a well-fitting bra. It is possible to tell that a bra fits well if the following apply:

  • The breast fills the cup without leaving any loose material and without the breasts bulging
  • The bra is not too loose or too tight
  • The straps do not dig into the flesh
  • The underband at the front lies close to the flesh and is at the same level as the strap at the back
  • Any underwire lies flat against the flesh and does not dig in or gape.

It has sometimes been suggested that women should not wear bras with an underwire during pregnancy because this can cause milk ducts to become blocked. However, there is no solid evidence to suggest this is the case and so long as the bra fits well and is not digging into the flesh, then wearing an underwire bra is not a problem. However, pregnant women may find a soft cup or maternity bra more comfortable to wear, particularly at night if extra support is needed while trying to sleep. Some bras are also designed not only to be more comfortable to sleep in, but to make nursing at night easier. Nursing bras can help to reduce discomfort and also allow breast pads to be used if women are experiencing leaks and are worried about liquid showing on their clothing.



Further Reading

  • All Pregnancy Content
  • Early Signs of Pregnancy
  • Is it Safe to Exercise During Pregnancy?
  • Pregnancy: 0-8 weeks
  • Pregnancy: 9 – 12 weeks

Last Updated: Jan 21, 2019

Written by

Sally Robertson

Sally has a Bachelor's Degree in Biomedical Sciences (B.Sc.). She is a specialist in reviewing and summarising the latest findings across all areas of medicine covered in major, high-impact, world-leading international medical journals, international press conferences and bulletins from governmental agencies and regulatory bodies. At News-Medical, Sally generates daily news features, life science articles and interview coverage.

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