Lactational mastitis



Lactational mastitis is a relatively common condition affecting post-partum women.

Also termed puerperal mastitis, it can affect up 1/3 of women in the post-partum setting (although many studies put this figure closer to 10%). It can be complicated by the development of a breast abscess. These terms may be defined as:

  • Mastitis: refers to inflammation of the breast tissue. Mastitis may be lactational (occurring in lactating women) or non-lactational. It can also be categorised as infectious or non-infectious.
  • Breast abscess: refers to a localised collection of pus within the breast. Again these may be lactational (occurring in lactating women) or non-lactational.

Prompt recognition and treatment tend to result in good outcomes though recurrence is common. Smoking, a major risk factor, should be discouraged when present.


Lactational mastitis affects around 10-33% of lactating women.

Incidence of lactational mastitis is highest in the 6 weeks following birth and gradually reduces with time. It is approximated that anywhere from 0.1% to 3% of lactating women will suffer with a breast abscess. This is increased in those with lactational mastitis to around 3% to 11%.


Lactational mastitis is normally caused by the blockage or reduced drainage of milk ducts.

In lactating women, milk stasis may occur due to blocked or reduced drainage of milk ducts. An inflammatory response occurs though this may not initially be infectious. However, static fluid eventually leads to bacterial proliferation.

There are a number of factors that predispose patients to mastitis. These include difficulty breastfeeding (e.g. due to poor attachment of the baby's mouth to the nipple) or reduced breastfeeding (e.g. weaning of breast milk):

  • Poor attachment to breast:
    • Cleft palate
    • Short frenulum
  • Reduced feeding (number or duration):
    • Rapid weaning
    • Unilateral feeding
    • Breast tenderness
  • Pressure on the breast:
    • Seat belts
    • Sleeping position
    • Tight bra

When infection occurs staphylococcus aureus (including MRSA, particularly in the inpatient setting) is most frequently implicated. Typically breast abscesses follow the development of mastitis, however, in some cases, mastitis may be absent or not clinically evident.


Efforts can be made to reduce the risk of lactational mastitis by addressing predisposing factors.

At booking (the first appointment with a midwife, scheduled early in pregnancy), women who are at increased risk of lactational mastitis can be identified. An example taken from Epsom and St Helier guidance advises identifying the following women:

  • Breast surgery (i.e. Augmentation/Reduction)
  • Problems relating to feeding her last baby
  • History of mastitis/breast abscess
  • History of Raynaud’s disease of the nipple, skin conditions on the breast or near the nipple area (e.g. psoriasis, eczema, nipple piercings)
  • Current un-investigated breast lump
  • Nipple piercing
  • Previous history of breast cancer/Paget's disease

These patients can be referred to an Infant Feeding Team (or a similar local group) for advice on techniques that may prevent or reduce the incidence of mastitis. Some risk factors (e.g. cleft palate) may be identified following birth but should be addressed.

Factors that may reduce the risk of mastitis include:

  • Ensure skin to skin contact following birth and during inpatient stay
  • Effective positioning and attachment during breast-feeding
  • Frequent and baby-led feeding
  • Avoiding nipple trauma through effective technique
  • Promoting mother/baby bond
  • Avoid the use of dummies
  • Hand expression of breastmilk when needed
  • Avoiding pressure on the breast

In those who are smoking, cessation should be strongly encouraged. General advice on good hygiene around breastfeeding and assist devices should be given.

Clinical features

Lactational mastitis often presents with pain, localised swelling and erythema.

Lactational mastitis tends to present unilaterally with a painful, often swollen and erythematous breast. The swelling may be in a wedge-shaped pattern. Close examination for any localised abscess is required.

  • Local signs of mastitis (typically unilateral):
    • Pain
    • Redness
    • Swelling
    • Hot
    • Lymphadenopathy (typically axillary)
  • Signs of systemic upset:
    • Malaise
    • Myalgia
    • Pyrexia
    • Tachycardia

Infective vs non-infective

It can be difficult to clinically distinguish between infective and non-infective mastitis. Consider the timing of the presentation and whether there is clinical improvement. After around 12 hours (if symptoms and blockage are not resolving), infection is likely due to ongoing milk stasis. Fissuring or evidence of nipple infection is also indicative of infective lactational mastitis.

Consider the patient's systemic status and observations. Investigations like breast milk cultures can be used to confirm infection.

Breast abscess

Some patients develop or present with a breast abscess. These are discrete collections of pus. Typically this will be apparent clinically with a tender fluctuant swelling. You should have a higher index of suspicion in those with recurrent mastitis or a previous abscess.

There may again be signs of systemic upset with malaise, myalgia, pyrexia and rarely haemodynamic instability. At times signs can be more subtle and an USS is be required to exclude it.


Simple lactational mastitis may be managed without additional investigations.

Investigations are not routine. The benefit should be considered in each individual. For example, any patient requiring hospital admission would need blood tests and cultures. However, patients who are well, without co-morbidity or other red flags may not need immediate investigations.


  • FBC
  • Renal function
  • CRP
  • LFTs
  • Lactate

Blood tests will generally be reserved for patients who are unwell, requiring inpatient management.


  • Breast milk culture: not routinely required and practice tends to vary. NICE CKS advises sending a sample if mastitis is severe or recurrent, there is a risk of hospital-acquired infection or a deep burning indicative of ductal infection. It is normally sent in any patient requiring hospital admission.
  • Blood cultures: arranged for inpatients with signs of systemic infection (e.g. pyrexia) and as a routine in any patient with immunosuppression or recent chemotherapy.


Breast USS: not used as standard. Indicated where symptoms are not improving to evaluate for an occult abscess.


Lactational mastitis may respond to conservative measures, require antibiotics and at times hospital admission.

Lactational mastitis often presents via GP and may be managed as an outpatient. In those with systemic signs of infection, immunosuppression or rapidly progressing symptoms arrange urgent (i.e. immediate) hospital admission.

Where a breast abscess is diagnosed or suspected refer urgently to breast / general surgery. In those with mastitis not improving, consider antibiotic resistance or an occult abscess (assess with USS).

NOTE: If there is any suspicion of breast cancer or a mass is felt an urgent referral should be made on the two-week wait breast cancer pathway.

Outpatient care

Patients who are systemically well, without significant co-morbidity and in the absence of rapidly developing symptoms or other cause for concern, management can be in the outpatient setting. A number of measures can give comfort and relieve symptoms:

  • Analgesia (e.g. ibuprofen, paracetamol)
  • Warm compress and warm water bathing

Mothers who are breastfeeding should be encouraged to continue this from both breasts wherever possible. If the breast is not completely empty (on the affected side), the remaining milk should be expressed (manual or with a breast pump).

Where it is not possible to continue breastfeeding (maternal preference, pain etc) mothers should be encouraged to express milk at least 8 times each day.

If symptoms worsen, do not improve after 12-24 hours of effective milk clearance or milk culture is positive, clinically reassess and again consider the need for inpatient care. If not required commence oral antibiotics, antibiotics should also be given where there is evidence of an infected nipple fissure. If there is a positive milk culture use an appropriate antibiotic as per the sensitivity of the organism. Empirical treatment may be in the form of:

  • Flucloxacillin 500 mg QDS for 10–14 days
  • Penicillin allergic:
    • Erythromycin 250–500 mg QDS for 10–14 days or
    • Clarithromycin 500 mg BD for 10–14 days

A history should be taken attempting to identify predisposing factors. Advice regarding breastfeeding technique and avoiding pressure on breasts may be required (see prevention section above). Consider referral to a specialist breastfeeding team.

Finally, appropriate safety netting is required. If antibiotics are commenced, advise returning if symptoms have not improved at 48 hours. Patients should return if they become unwell, feverish, symptoms worsen or they have any concerns.

Inpatient care

Those with systemic signs of infection, immunosuppression or rapidly progressing symptoms require urgent hospital referral and review. Any patient presenting with signs of sepsis should be managed in line with the sepsis 6 principles with an immediate senior review.

Patients may require intravenous fluids and antibiotics and close clinical review. The measures described above (analgesia, milk expression) should be adhered to.

Breast abscess

The development of a breast abscess requires urgent referral to hospital and a surgical review. As described above any patient presenting with signs of sepsis should be managed in line with the sepsis 6 principles with an immediate senior review.

Appropriate investigations including blood and milk cultures should be sent. Intravenous antibiotics should be commenced in line with local microbiology advice. The two main surgical techniques to treat an abscess are:

  • Incision and drainage
  • Needle aspiration

Last updated: March 2021

Further reading

NICE CKS: Mastitis and breast abscess

La Leche: Information for patients on mastitis

Author The Pulsenotes Team A dedicated team of UK doctors who want to make learning medicine beautifully simple.

Pulsenotes uses cookies. By continuing to browse and use this application, you are agreeing to our use of cookies. Find out more here.