Breast Enlargement in Infants
Premature start is a condition in which the breasts of baby girls begin to enlarge. It is usually a temporary, harmless condition. Breast enlargement in infants and young girls is sometimes the first sign of early (precocious) puberty, but this is uncommon.

What is premature start?

Premature start is enlargement of the breasts in infant girls. Most often, breast enlargement is the only abnormality. It is occasionally the first sign of early (precocious) puberty. This is more likely if the breasts become enlarged after ages 2 to 3.

Usually there is no apparent cause of early breast enlargement, although it can result from exposure to medications or to sources of the hormone estrogen. The breasts may remain enlarged for as long as a few years but eventually go down in size before your daughter starts puberty.

What does it look like?
  • Your daughter’s breasts start getting bigger.  
  • One or both breasts may be enlarged. They may go up and down in size.
  • Breast enlargement usually occurs before age 2. Occasionally, a baby girl is born with enlarged breasts.
  • There are no other signs of puberty, for example, growth of pubic hair (hair around the genitals) or rapid body growth.
  • Medical tests, if performed, show no other signs of approaching puberty.
  • Breasts eventually stop growing and may become reduced in size. It may take a few years before the breasts completely return to normal. Girls go on to have a normal puberty.
What causes premature start?
  • Usually, no specific cause is identified.
  • Premature breast enlargement can be caused by exposure to the hormone estrogen, for example, a child eating the mother’s birth control pills.
What are some possible complications of premature start?
  • Usually none. The condition often goes away on its own, although this may take a few years.
  • Infrequently, premature start is the first sign of early (precocious) puberty. This is most likely when the breasts start to enlarge after ages 2 to 3, accompanied by other signs of puberty such as an enlarged clitoris or development of pubic hair. Treatment may be needed to halt the process of early maturation.
What puts your child at risk of premature start?

There are no known risk factors.

Can premature start be prevented?

There is no way to prevent this condition.

How is premature start treated?
  • Usually, no treatment is needed. Your daughter’s breasts will eventually go down in size or stop enlarging.
  • Your doctor will examine your child for any other signs of puberty. Medical tests are usually not needed. If the doctor has any reason to suspect an abnormality, various tests may be performed as well, such as measuring hormone levels, x-rays to assess bone growth, or ultrasound scans of the uterus and ovaries.
  • The doctor will continue to monitor your daughter to make sure there are no other signs of early puberty.
  • If there is any reason to suspect a medical cause of early puberty, we will probably recommend a visit to an endocrinologist (a doctor specializing in the treatment of gland and hormone diseases). This specialist can perform tests and recommend treatments designed to interrupt the process of puberty, if necessary.
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