8 Reasons Why Your Breast Size May Increase Suddenly

Have you recently noticed that your lingerie is getting a tad bit tighter? Breast tissue is primarily made up of layers of fat, so minor changes in breast size are common. However, if you notice that the difference is sudden, significant, or increasing over time, it is good to evaluate some of these causes.

1. Puberty

Puberty would inevitably cause your breasts to increase in size


Puberty is the most common reason for an increase in breast size in girls. In fact, breast enlargement often precedes the first period by 2 years or more. So, if you are concerned that the young woman in your life is suddenly developing breasts, it could simply be that she is approaching puberty. The real problem arises when the child is younger than 12 and seems to be racing toward puberty at a rapid pace. A serious issue like hyperthyroidism can be at play here.1 2

2. Cancer

Cancerous cells in the breasts could make it bigger


Breast cancer is one of the leading causes of death around the world. Triggers for breast cancer include smoking, obesity, as well as hereditary conditions that make cancer more likely for some people. If you notice that one of your breasts is larger than the other or if you have a lump in your breast that seems to be growing, it could be early signs of breast cancer.

Sometimes, you may experience a lump in the breast that disappears after your period. Do not be alarmed by this. Such lumps are usually caused by hormones and not due to breast cancer.3


3. Weight Gain

You could get large breast simply because you put on more weight

It is quite natural to pack on some pounds as you grow, either due to a changed lifestyle or different food and exercise habits. In such cases, it is common for your breasts to grow proportionately. However, weight gain and obesity can put you at greater risk for breast cancer, so it advisable to shed some weight. In some cases, if you cannot spot a definite reason for weight gain, you might be facing a hormonal imbalance that needs to be looked at.4


4. Breast Lumps

Breast lumps that may not be cancer could increase the breast size

As discussed earlier, lumps can appear and disappear in breast tissue over time. These lumps are often harmless, although some can be painful. A breast lump can cause one or both breasts to look larger and feel heavier.5 6


To be on the safer side, conduct a breast self-examination every month to understand what your breasts usually look and feel like. This will allow you to evaluate easily if the lumps are something new and harmless or not. If lumps are a common occurrence during menstrual cycles, it may not always be a cause for concern.7

5. Periods

Your menstrual cycle would result in increased breast size


Many women report that their breasts feel tender and slightly swollen during a menstrual period. This kind of enlargement disappears around the 5th day of the cycle. If you visit a doctor about this issue during your period, you may be asked to come back at a different time in the cycle for an accurate diagnosis.8

During menstruation, the milk glands in the breasts become larger as they are preparing for a possible pregnancy. This is why the breasts are larger during a period. However, once the hormone levels settle through the cycle, the breasts go back to their usual size.


6. Pregnancy

Pregnancy results in change in hormone levels resulting in large breasts

Lactation follows pregnancy quite closely. From the time you are pregnant, your breasts begin to grow in size in preparation for the baby and the demand for milk. In the last trimester, many women even report seeing some small amount of white discharge from the breasts, which are precursors for breast milk. For many, the change in breast size at pregnancy is often permanent. It may be wise to shop for new lingerie!9

7. Childbirth

Childbirth could cause your breast size to increase

If you thought your breasts are big during pregnancy, wait until lactation comes along! Once the baby stimulates milk production with the suckling, milk begins to flow rapidly and occupies the breast tissue, leading to unusually enlarged breasts. As long as a feeding schedule is established, both the baby and you should be fine.

When are lactation and breast size a concern? Sometimes, the milk in the breasts can cause inflammation, damaging the surrounding tissue, which will require medical care. Known as mastitis, swollen breasts accompanied by unease and a high body temperature must be reported immediately to a doctor.10

8. Other Causes

Other minor causes could be intercourse or tight innerwear

Some sources report that increased sexual activity can also cause an increase in breast size. However, there are no studies to back this claim. In most cases, merely wearing the wrong bra leaves you breathless. This can make you feel as though your breast size has gone up. In such cases, it is best to try out a different inner garment for a few days before jumping to the worst possible conclusion.

If the lumps in your breast or a difference in breast size persist for a long time, consult a doctor to rule out any severe health issues. Most times, the breasts get back to their original size before you even notice.