If you're pregnant now or have been in the past you've probably noticed the change in your bra cup size. These physical changes along with tender swollen breasts may have been one of the earliest clues that you have successfully conceived. Some experts believe that the colour change in your areola may also be helpful when it comes to breastfeeding.



What's even more remarkable than the visible changes or ones that you can feel are the extensive changes that are happening inside your breasts underneath the skin. A complex biological process is taking place that makes lactation possible and this is stimulated into action by a developing placenta causing the release of estrogen and progesterone into your body.

Prior to pregnancy, the larger portion of your breasts are made up of supportive tissue, milk glands and fat. Your swollen breasts have been preparing for reproduction for the entire time that you have existed!

By the time you were born your main milk dusts had already been formed. When you reached puberty a flood of the female hormone estrogen was responsible for causing your mammary glands to grow and swell. During your pregnancy these glands go into overdrive with the increased amounts of estrogen.

Prior to your baby's arrival glandular tissue replaces the majority of your fat cells and this is what makes your breasts larger than before. Each breast may increase by up to one and a half extra pounds.

Among this mass of your fatty cells and glandular tissue is an intricate network of canals or channels which are your milk ducts. The hormones released during your pregnancy cause these ducts to increase both in number and size and these ducts branch off into smaller canals near your chest wall known as ductules.

A cluster of smaller sacs are located at the end of each duct which are known as alveoli. Each cluster of alveoli is called a lobule and each cluster of lobules is called a lobe. Each one of your breasts will contain around 15-20 lobes with one milk duct for each lobe.

Your milk is produced inside your alveoli which is surrounded by tiny muscles which squeeze the glands and help to push your milk out into the ductules. Leading on from the ductules are larger ducts which then widen into a milk pool directly beneath the areola.

These milk pools then act as reservoirs that hold your milk until your baby sucks it through the tiny openings in your nipples.

Amazingly, nature ensures that your complete milk producing system is fully developed around the time of your second trimester thereby ensuring that you are able to breastfeed your baby even if there's an unexpected early arrival.