Breast Changes During Pregnancy: Week By Week

By Sharon Thomas

Remarkable changes can be seen in the body during the phase of pregnancy in a woman. These changes can happen throughout - at the onset, during carrying, and even after delivery. Mothers embrace this stage in their lives to the core. It is natural that the body gets ready to welcome the infant right from the time of conception and adjusts itself accordingly. The major transformation that happens is to the breasts. Mammary gland is another name for the breast in females. It is derived from the Latin word 'mamma'.

breast changes during pregnancy: week by week

Breasts ready themselves to feed the newborn. The only one most common thing that everyone knows is that the breast becomes bigger in size. There are hundreds of other things that cater to the massive change and it happens over a period of time, not all of a sudden. These changes can be tracked week by week and a glimpse of it is described below.


Week 1 To 4

Week 1 is the follicular and ovulatory phase of the egg in the womb. The first change that happens to the breast is the growth of milk ducts and alveolar buds. These changes hit the peak during the second week when the egg gets fertilised. Tenderness in the breasts can be experienced around the third week and this is considered as one of the earliest signs of pregnancy. Blood supply to the breasts increases by the time of the fourth week, creating sensitivity around the nipples. So, a tingling and pricking sensation is most common at this time. Rapid reproduction of milk-producing cells takes place.


Week 5 To 8

The cell structure of the breasts undergoes a massive change to support the supply of milk. Hormones called placental lactogens interact with the breasts. The growth of glandular tissue make the breasts feel fuller and the lady might feel uncomfortable. It also happens because the milk ducts begin to swell. The pigment around the nipples starts getting darker to help the baby locate it while feeding. The nipples start to stick out unusually. All these happen around the fifth and sixth weeks. During the seventh week, breast grows in weight to even 650 g on each side due to oestrogen and progesterone. An effect called ‘marbling' takes place in the eighth week under the skin of the breasts. This is nothing but the growth of veins to help in better blood supply. Small bumps called Montgomery tubercles, between 4 and 28, develop around the nipples to keep the skin soft and discourage bacteria.


Week 9 To 12

The areola keeps darkening and increases in diameter in the ninth week. In addition, a secondary areola develops. It is nothing but a light-coloured tissue around the dark areola. It might not be visible in women with light complexion. Week 10 is the time to go for a bigger bra as major breast growth is over by this time. Nipple inversion is likely to happen in the 12th week, especially for first-time moms but this gets corrected as the pregnancy progresses.


Week 13 To 16

The blood circulation drastically increases in the 13th and 14th week. The areola may even look speckled. Breast tenderness mostly goes away by the 16th week. A straw-coloured sticky fluid can be expressed from the breasts now. This is the fluid that the baby takes in for a few days until the milk comes in after delivery. It is called colostrum and it contains all the essential nutrients for the baby. It also gives the necessary resistance power. Drops of blood might be visible due to increased blood vessels. This is common but it is safe to consult your doctor in this case.


Week 17 To 20

Fat gets accumulated in the breasts in the 18th week. Lumps may begin to appear on the breasts for some women. The types of lumps that may appear are cysts, galactoceles, and fibroadenomas. In most cases, the lumps are noncancerous. 20th week is the time for the stretch marks to appear, especially on the underside of the breasts. This is due to the stretching of the skin. Some lucky ones may not even get them.


Week 21 To 24

The breasts have now grown to a bigger size than before. It is a good idea to shop for a new bra. Prefer cotton to other materials, as the breasts tend to sweat a lot because of the fat that has accumulated. It is also advised not to choose under-wired bras to allow the free flow of blood in the veins.


Week 25 to 28

In the 26th week, the breasts become fuller and pendulous for some. Frequent leakage of colostrum can be seen. This need not happen to every pregnant woman. The breasts actually are ready to produce milk by the 27th week for your baby. It is the progesterone that prevents the secretion of mature milk until the baby is delivered. By the 28th week, blood vessels below the surface of the skin start getting visible and alongside, the pigmentation around the nipples and blood circulation increases. Milk ducts start to dilate.


Week 29 To 32

Sweat rash on the breasts is one problem that happens around the 30th week. This is because the mucus membranes and blood vessels get dilated due to high blood flow. Sweat rash must be treated to avoid further infection. Week 32 is the time to avoid using soap on the breasts, as the small bumps around the nipples produce a creamy sebum to keep the skin moist. Stretch marks become more visible.


Week 33 To 36

Along with the sebum secretion, some colostrum also finds its way out of the nipples. Increased progesterone makes the nipple more prominent and mobile than before. A nursing bra can be purchased during the 36th week, as most part of the growing is done by now. One must also take into account that the breasts will get bigger a little more when the milk production starts and get back to normal again. So, choose the size wisely.


Week 37 To 40

The colour of the colostrum changes from thick and yellow to pale and colourless. Breasts are fully mature by the 38th week. Oxytocin, the hormone which induces contraction, gets released when the breasts are manipulated by hand.

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