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. 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. Glands on the areola called Montgomery glands become raised, bumpy and more obvious.
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.
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.
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 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.