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Puerperal Mastitis

Mastitis means inflammation of the breast, and may be non-infectious or infectious in origin. In lactating women, it is essentially caused by an accumulation of milk.


Between 10% and 33% of breast-feeding women develop lactation mastitis. The incidence is highest in the first few weeks postpartum, decreasing gradually after that. However, cases may occur as long as the woman is breast-feeding.

Predisposing factors

Puerperal mastitis may or may not be associated with infection.

Non-infectious mastitis is due to an accumulation of milk causing an inflammatory response in the breast.

Infectious mastitis occurs when accumulated milk allows bacteria to grow. The usual infecting organism is Staphylococcus aureus, although it may also be Staphylococcus albus and streptococci. Meticillin-resistant Staphylococcus aureus (MRSA) infection is increasing, and may be more common in women who have had a caesarean section.

Infectious mastitis may lead to a breast abscess, which occurs when a localised collection of pus develops.

Risk factors

Problems with attachment of infant to breast during feeding, due to problems with technique or anatomical anomalies such as tongue-tie or cleft lip.

Reduced number of feeds, or duration of feeds, leading to milk accumulation. This may be due to:

Partial bottle feeding.

Changes in regime (due to infant starting to sleep through the whole night for example).

Rapid weaning.

Painful breasts.

Preferred breast, leading to milk accumulation in the other.

Pressure on the breast – due to tight clothing, seat belt, sleeping in the prone position.

Nipple fissures, cracks and sores.

Trauma to breasts.

Blocked milk ducts.


Mastitis is diagnosed based on clinical symptoms and signs indicating inflammation – breast pain along with systemic features.


This normally presents ≥1 week postpartum usually in only one breast. The area affected is painful, tender, red and hot.

Systemic symptoms include fever, rigors, muscle pain, lethargy, depression, nausea and headache. It should be distinguished from congestive mastitis (breast engorgement), which usually presents on the second or third day of breast-feeding. The complaint in this case is of swollen and tender breasts bilaterally, without fever or erythema.


Breast examination reveals unilateral oedema, erythema in a wedge-shaped area, and tenderness. The affected area feels firm and hot.

There may be fever.

It is not possible to distinguish clinically between infectious and non-infectious mastitis.

If a breast abscess has developed, there will be a fluctuant tender lump, with overlying erythema. Axillary lymphadenopathy may be palpable.


Diagnosis is usually clinical. Detection of pathogens in breast milk is not always possible, and the results of milk culture may not be a useful guide for therapy. The agents most frequently identified in milk culture are S. aureus and coagulase-negative Staphylococcus spp. However, these may be contaminants or skin flora. MRSA is increasing in incidence. Milk should be cultured if infection is severe or recurrent, or is not starting to resolve after two days of antibiotics, or if infection has been acquired in hospital.

If an abscess is suspected, early referral is required. Ultrasound will show whether there is a collection of pus and should also be considered when infection does not settle after one course of antibiotic.


First-line management

Reassurance. Mastitis is painful, but should not interfere with ability to breast-feed, or affect the long-term appearance of the breast.

Encourage the woman to continue breast-feeding. Explain that to do so will not cause any harm to the baby. If it is too painful, consider feeding via expressing until symptoms improve.

Improve milk removal. This may involve:

Assessment of breast-feeding technique by an appropriately trained, skilled person who can assess feeding pattern, positioning, attachment, sucking behaviour and breast fullness.

Manual expression of milk to empty the breast after feeding.

Self-massage of the breast before feeding or expression, or application of heat by warm compresses, shower or heat packs.

Increasing feeding frequency.

Feeding on the affected side first while symptoms persist so this breast is emptied most effectively.

Analgesia. Paracetamol or ibuprofen may be used for pain and inflammation where appropriate.

Advise not wearing a bra at night.

Be aware that many women may require emotional support.


Guidelines such as those by the World Health Organisation (WHO) and the Academy of Breastfeeding Medicine suggest first-line measures for 24 hours before starting antibiotics unless the woman is acutely unwell or has an infected nipple injury.

Antibiotics, usually flucloxacillin or erythromycin, should be prescribed. Treatment should be in accordance with local prescribing guidelines.

Surgical management

Surgical management is indicated for breast abscesses. Incision and drainage of abscess with cavity packed open with gauze is recommended if the overlying skin is thin or necrotic.

Parenteral antibiotics should be administered at the same time, with added coverage for anaerobic bacteria. Fluid from the abscess should be cultured, and results used to determine ongoing antibiotic treatment.

Needle aspiration of the abscess, repeated every other day until the pus no longer accumulates, has been suggested as an alternative to open drainage.

In some cases breast-feeding may have to cease until the abscess is successfully treated, but can usually resume later.

Any persisting mass will need further investigation to exclude sinister causes.


Cessation of breast-feeding is the most common complication of mastitis. This may lead to emotional distress in women who had planned to continue breast-feeding.

Serious complications occur in cases where treatment is delayed, incorrect or ineffective. These include breast abscess and sepsis. Breast abscesses occur in around 3-7% of women with puerperal mastitis. Stopping breast-feeding suddenly in mastitis increases the risk of developing an abscess. Other risk factors include obesity and smoking.​