What Causes Lumps In Baby Breast And Should You Be Worried?

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Baby breast lump or enlargement is a common occurrence among newborns and usually nothing to worry about. The condition is visible as lumps under the nipple. A baby breast lump could be present in one or both the breasts and affect boys and girls alike.

Most cases of breast lumps in babies subside without any treatment. However, you may still consult a pediatrician to rule out any underlying issues.

Read on to learn about the causes of baby breast lumps, when they disappear, and when to consult a doctor.

Causes Of Breast Lumps And Enlargement In Babies

The following factors may lead to the formation of breast lumps in babies.

1. Maternal hormonal changes

During pregnancy, there is an increase in the levels of estrogen hormone, which could pass into the baby inside the womb (1). The hormone’s effects could persist after birth, and some babies may develop breast lumps a few days after birth. A mother will also produce high levels of prolactin hormone, which enables milk production in her. Prolactin may also pass into the baby inside the womb, causing breast lumps after birth. Some babies may even secrete a bit of breast milk, also called Witch’s milk, due to the effects of the hormone (2).

Maternal hormones are the most common cause of baby breast lumps. Studies suggest that maternal estrogen usually causes some degree of breast enlargement in nearly 70% of newborns (3).

2. Isolated premature thelarche

Premature thelarche is the condition where a girl shows breast development before the age of eight years (4). Infants and toddlers usually experience isolated premature thelarche, which is breast enlargement without precocious puberty (early puberty) (5).

Isolated premature thelarche usually occurs due to maternal hormones. Some rare causes include ovarian cysts and precocious puberty.

3. Medications

If the mother is exposed to certain medications during pregnancy, it may cause a surge in hormones. These hormones could pass into the baby and lead to the formation of breast lumps in newborns. In rare cases, a baby might develop breast lumps as a side effect of a medicine.

4. Infections and disorders

In rare cases, infections and disorders may lead to the formation of breast lumps in babies. Babies who experience endocrine disorders, such as thyroid disorders, may experience premature thelarche with precocious puberty (6). Some less common causes of baby breast lumps include problems with the central nervous system, genetic disorders, and breast tumors (7).

Neonatal mastitis (infection of the breasts) may cause swelling beneath the nipples (8). The causative agents of the infection are similar to those seen in mastitis in adults. Staphylococcus and Streptococcus bacteria are some of the leading causes. A baby with breast lumps due to a bacterial infection will generally display other signs, such as fever, fussiness, and lethargy.

5. Congenital deformities

Some babies may experience congenital deformities in the nipple or the tissues of the chest (9). It may cause the appearance of enlarged breasts. In rare cases, the baby might be born with a benign breast tumor or vascular (blood vessel-related) deformations, which may render the breast a swollen appearance.

When Do Breast Lumps In A Baby Go Away?

Breast lumps due to maternal hormones usually subside within two weeks (1). The reduction of breast lumps due to other causes may depend on several factors, such as the type of cause, the severity of the cause, and if the condition requires treatment. In most cases, the appropriate treatment or management causes the breast lumps to go away within days to weeks.

Certain causes, such as congenital deformities and severe endocrine disorders, may require extensive long-term treatment. You may speak to a pediatrician to determine the treatment and the prognosis of the condition.

When To Consult The Doctor?

A pediatrician is likely to assess the presence of any breast anomalies at birth and during a routine check-up.

You may consult a pediatrician in the following cases.

  • The lumps do not subside after two weeks.
  • The lumps constantly enlarge.
  • You notice redness on the swollen breast.
  • You notice nodules on the enlarged breasts.
  • The nipples ooze pus.
  • The baby itches the breast lump often.
  • The baby has signs of infection, such as fever, fussiness, and loss of appetite.

The doctor may advise tests, such as blood tests, mammography, and magnetic resonance imaging (MRI), depending on the severity of signs and symptoms. Breast lumps due to maternal hormones do not require any treatment. Other causes of breast enlargement may require appropriate treatment.

Dos And Don’ts With Breast Lumps In Babies

Keep in mind the following points if your baby has enlarged breasts.

  • Never pinch the lumps as it may cause irritation and infection.
  • Do not squeeze the milky liquid or the Witch’s milk. Let the secretion subside naturally.
  • Clean any secretion from breasts with a moist, soft cloth.
  • Keep the nipple and the surrounding skin clean.
  • Maintain the usual feeding pattern for the baby.

Breast lumps in babies could concern parents, but it is seldom harmful and subsides on its own in a few weeks. Stay observant of any changes in the size of the breast lumps. If you suspect any changes or notice any abnormal signs, consult a pediatrician for prompt diagnosis and treatment.


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1. Hormonal effects in newborns; U.S. National Library of Medicine
2. T. Forbes, Witch’s Milk and Witches’ Marks; Semantic Scholar
3. V Raveenthiran, Neonatal Mastauxe (Breast Enlargement of the Newborn); Journal of Neonatal Surgery; NCBI
4. Prithi R Inamdar et al., Isolated premature thelarche: A normal growth variant; Journal of the Scientific Society
5. Dr Yuranga Weerakkody et al., Premature thelarche; Radiopaedia
6. Precocious Puberty; Stanford’s Children Health
7. Ayman Al-Jazaeri et al., Unilateral breast mass in an infant: a rare presentation of spontaneously regressing myofibromatosis; NCBI
8. Nahar AL Ruwaili and Dennis Scolnik, Neonatal Mastitis: Controversies in Management; Journal of Clinical Neonatology; NCBI
9. Breast and Chest Wall Disorders; Children’s Hospital of Philadelphia