INTRODUCTION — Lactational mastitis is a condition in which a woman's breast becomes painful, swollen, and red; it is most common in the first three months of breastfeeding. Initially, engorgement occurs because of poor milk drainage, probably related to nipple trauma with resultant swelling and compression of one or more milk ducts. If problems with drainage persist beyond 12 to 24 hours, the stagnant milk becomes infected and lactational mastitis develops (since breast milk contains bacteria); this is characterized by pain, redness, fever, and malaise [1].
Issues related to lactational mastitis will be reviewed here. Issues related to other breast infections are discussed separately. (See "Nonlactational mastitis in adults" and "Primary breast abscess" and "Breast cellulitis and other skin disorders of the breast".)
In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transgender and gender-expansive individuals.
EPIDEMIOLOGY — Lactational mastitis has been estimated to occur in 2 to 10 percent of breastfeeding women [2]. The incidence of mastitis requiring hospitalization is low; in one cohort including 136,459 new mothers, 127 women were hospitalized for mastitis, an incidence of 9 per 10,000 deliveries [3].
The risk of recurrence of mastitis in women with prior history of lactational mastitis is higher than in women with no prior history.
ETIOLOGY — Lactational mastitis often occurs in the setting of breastfeeding problems that typically result in prolonged engorgement or obstructed milk drainage [4]:
●Nipple excoriation or cracking
●Partial or total blockage of milk duct; reduced drainage results in stagnant milk distal to the obstruction
●Oversupply of milk
●Infrequent feedings
●Rapid weaning
●Illness in mother or baby
●Maternal stress or excessive fatigue
●Maternal malnutrition
Organisms grow in the stagnant milk, resulting in infectious mastitis [1]. Infection can progress to local abscess formation if not treated promptly. Effective management and prevention of recurrence depends on resolution of the above factors.
Risk factors for lactational mastitis include prior history of mastitis, poor milk drainage, cracked nipples, use of cream on nipples (particularly antifungal cream), and using a breast pump [4,5].
The pathogenesis of lactational mastitis is complex and may include poorly understood interactions between the mammary-associated microbiota and host-specific genetic factors [6].
The risk of developing lactational mastitis can be reduced by frequent, complete emptying of the breast and by optimizing breastfeeding technique [7].
MICROBIOLOGY — Most episodes of lactational mastitis are caused by Staphylococcus aureus. Methicillin-resistant S. aureus (MRSA) has become an important pathogen in cases of lactational mastitis [2,8]; in one study including 127 women hospitalized for mastitis, MRSA was the most common pathogen isolated from women with mastitis alone (24 of 54 specimens) or mastitis and abscess (18 of 27 specimens).
Less frequent pathogens include Streptococcus pyogenes (group A or B), Escherichia coli, Bacteroides species, Corynebacterium species, and coagulase-negative staphylococci (eg, Staphylococcus lugdunensis).
In one study, milk was cultured from 192 women with mastitis and 466 breast milk donors (controls); two organisms, S. aureus and group B streptococci, were recovered significantly more frequently from women with mastitis than controls [1]. S. aureus has been widely reported as a causative organism in mastitis [9-11].
CLINICAL MANIFESTATIONS — Lactational mastitis is a condition in which a woman's breast becomes painful, swollen, and red (picture 1); it is most common in the first three months of breastfeeding. Initially, engorgement occurs because of poor milk drainage, probably related to nipple trauma with resultant swelling and compression of one or more milk ducts.
If symptoms persist beyond 12 to 24 hours, the condition of infectious lactational mastitis develops (since breast milk contains bacteria) [1]. Infectious lactational mastitis typically presents as a firm, red, painful, swollen area of one breast associated with fever >38.3ºC in a nursing mother; milk secretion may be diminished. Systemic complaints may include myalgia, chills, malaise, and flu-like symptoms.
In the early stages, the presentation can be subtle with few clinical signs; patients with advanced infection may present with a large area of breast swelling with overlying skin erythema. Reactive axillary lymphadenopathy may be associated with axillary pain and swelling.
DIAGNOSIS — The diagnosis of mastitis is based on clinical manifestations; laboratory tests are not needed.
Culture of the breast milk can be useful to guide selection of antibiotics; it is particularly important in the setting of infection that is severe, hospital acquired, or unresponsive to initial empiric antibiotics [7,12]. Blood cultures are warranted in the setting of severe infection (eg, hemodynamic instability, progressive erythema) but are otherwise not routinely necessary.
Imaging is useful if lactational mastitis does not respond within 48 to 72 hours to supportive care and antibiotics. Ultrasound is the most effective method of differentiating mastitis from breast abscess [13-17]. (See "Primary breast abscess".)
DIFFERENTIAL DIAGNOSIS
●Severe engorgement – Engorgement occurs due to interstitial edema with onset of lactation or at other times with accumulation of excess milk. Mastitis may be distinguished from severe engorgement in that engorgement is bilateral, with generalized involvement [2]. Engorgement is not typically associated with systemic symptoms of fever and myalgia. (See "Common problems of breastfeeding and weaning", section on 'Engorgement'.)
●Breast abscess – Mastitis can progress to local abscess formation if not treated promptly. A tender fluctuant area is suggestive of an abscess [18]. Ultrasonography is the most effective method of differentiating mastitis from a breast abscess and also facilitates guided drainage (image 1) [13-17]. (See "Primary breast abscess".)
●Plugged duct – A plugged duct is a localized area of milk stasis within the milk duct that causes distention of mammary tissue. Symptoms include a palpable lump with tenderness. A plugged duct may be distinguished from mastitis and breast abscess by the absence of systemic findings. (See "Common problems of breastfeeding and weaning", section on 'Plugged ducts'.)
●Galactocele – A galactocele (also known as a milk retention cyst) is a cystic collection of fluid that is usually caused by an obstructed milk duct. Galactoceles present as soft cystic masses; they are not tender and are not associated with systemic manifestations. Ultrasonography may demonstrate a simple milk cyst or a complex mass. The diagnosis can be made on the basis of the clinical history and needle aspiration, which yields a milky substance. (See "Common problems of breastfeeding and weaning", section on 'Galactoceles'.)
●Inflammatory breast cancer – Inflammatory breast cancer (IBC) should be considered if mastitis does not resolve with appropriate treatment. Erythema may improve to some degree with antibiotics in patients with IBC, but there are usually other manifestations of IBC present; IBC may be differentiated from mastitis by clinical manifestations of skin thickening due to edema, erythema, and peau d'orange appearance (picture 2 and picture 3 and picture 4). It is often associated with palpable axillary lymphadenopathy due to metastatic nodal involvement. The diagnosis is established via core biopsy. (See "Inflammatory breast cancer: Clinical features and treatment".)
The differential diagnosis of nonlactational mastitis is discussed separately. (See "Nonlactational mastitis in adults".)
TREATMENT
Clinical approach — Initial management of nonsevere lactational mastitis consists of several interventions aimed at relieving pain and maintaining milk flow through the milk ducts of the breast [19]:
●We provide the following guidance to patients [7,10-12,14,18,20]:
•For pain relief, use cold compresses or soak a cloth in warm water and place it on your breast. A warm shower or bath may also help. Acetaminophen or ibuprofen can also be used for relief of pain and fever (aspirin should be avoided).
•Rest and drink plenty of fluids.
•If you are breastfeeding, continue to breastfeed. Start feeds with the sore breast first.
•Express or pump milk from your breast between feeds.
•Massage your breast to clear any blockages – stroke from the lumpy or sore area towards your nipple to help the milk flow.
•Avoid tight-fitting clothes or bras.
When there are concerns for infection (ie, symptoms persist beyond 12 to 24 hours and are accompanied by fever or systemic symptoms), treatment additionally includes antibiotic therapy with activity against S. aureus [9,10,12,13,20-29]. In one observational study, when infectious lactational mastitis was treated with antibiotics in addition to breast emptying, the rate of symptom resolution within two weeks increased from 50 to 96 percent [10]. (See 'Antibiotic therapy' below.)
If there is no clinical improvement within 48 to 72 hours, evaluation with ultrasound imaging to determine if there is an underlying abscess should be pursued. (See "Primary breast abscess".)
Antibiotic therapy — Culture of the breast milk can be useful to guide selection of antibiotics and is particularly important in the setting of severe, healthcare-acquired, or refractory infection [7,12]. Blood cultures are warranted in the setting of severe infection (eg, hemodynamic instability, progressive erythema) but are otherwise not necessary.
Empiric therapy for lactational mastitis should include activity against S. aureus [10,20]:
●In the setting of nonsevere infection in the absence of risk factors for methicillin-resistant S. aureus (MRSA) (table 1), outpatient therapy may be initiated with dicloxacillin (500 mg orally four times daily) or cephalexin (500 mg orally four times daily) [20]. In the setting of beta-lactam hypersensitivity, erythromycin 500 mg twice daily is preferred. Clindamycin 450 mg orally three times per day may also be used although caution is warranted because of the risk of Clostridioides difficile colitis.
●In the setting of nonsevere infection with risk for MRSA (table 1), effective antibiotics include trimethoprim-sulfamethoxazole (TMP-SMX; 1 double-strength tablet orally twice daily) or clindamycin (450 mg orally three times daily).
TMP-SMX may be used in women who are breastfeeding healthy full-term infants who are at least one month old. TMP-SMX should be avoided in women who are breastfeeding newborn infants (<1 month old) or infants with glucose-6-phosphate dehydrogenase deficiency, and it should be used cautiously in women who are breastfeeding infants who are jaundiced, premature, or ill [30]. (See "Trimethoprim-sulfamethoxazole: An overview", section on 'Pregnancy and breastfeeding'.)
●In the setting of severe infection (eg, hemodynamic instability, progressive erythema on antibiotics), empiric inpatient therapy with vancomycin (table 2) should be initiated; therapy should be tailored to culture and sensitivity results. Gram stain results demonstrating gram-negative rods should prompt empiric antibiotic therapy with a third-generation cephalosporin or a combination beta-lactam-beta-lactamase agent.
The optimal length of therapy is not certain; 10 to 14 days may reduce the risk of relapse, but shorter courses (5 to 7 days) can be used if the response to therapy is rapid and complete. In patients with severe mastitis or abscess, once there are signs of clinical improvement with no evidence of systemic toxicity, antibiotics may be transitioned from parenteral to oral therapy.
PREVENTION — For pregnant women with a history of lactational mastitis, administration of a Lactobacillus probiotic during late pregnancy may reduce the likelihood of lactational mastitis. In one randomized trial that included 108 pregnant women with history of infectious mastitis after previous pregnancies, women who received oral Lactobacillus salivarius PS2 had a lower incidence of mastitis than those who received placebo (25 versus 57 percent) [6].
There is insufficient evidence to support administration of prophylactic probiotic therapy for pregnant women with no history of lactational mastitis [31].
RECURRENCE — Recurrent mastitis is uncommon but can result from inappropriate or incomplete antibiotic therapy and/or failure to correct problems with breastfeeding technique associated with incomplete milk drainage. Inflammatory breast carcinoma should be considered in the setting of mastitis that recurs repeatedly in the same location and/or does not respond to antibiotic therapy. (See 'Differential diagnosis' above.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Breastfeeding and infant nutrition".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Common breastfeeding problems (The Basics)")
●Beyond the Basics topic (see "Patient education: Common breastfeeding problems (Beyond the Basics)")
SUMMARY
●Definitions – Lactational mastitis is a condition in which a nursing person's breast is painful, swollen, and red. It can be noninfectious or infectious. (See 'Introduction' above.)
●Etiology – Breastfeeding problems that cause prolonged engorgement or obstruct drainage can result in lactational mastitis. Breast milk can contain bacteria, and incomplete breast emptying causes the organisms to grow and proliferate. (See 'Etiology' above.)
●Microbiology – Most episodes of infectious lactational mastitis are caused by Staphylococcus aureus. Methicillin-resistant S. aureus (MRSA) has become an important pathogen. (See 'Microbiology' above.)
●Clinical manifestations – Infectious lactational mastitis typically presents as a firm, red, tender, swollen area of one breast associated with fever >38.3ºC in a nursing patient. Systemic complaints may include myalgia, chills, malaise, and flu-like symptoms. It is most common during the first three months of breastfeeding. (See 'Clinical manifestations' above.)
●Diagnosis – Infectious lactational mastitis is diagnosed whenever lactational mastitis persists beyond 12 to 24 hours and is characterized by breast pain, swelling, and erythema accompanied by fever and malaise.
●Evaluation – Culture of the breast milk can be useful to guide selection of antibiotics; it is particularly important in the setting of infection that is severe, hospital-acquired, or unresponsive to initial antibiotics. Imaging is useful if lactational mastitis does not respond within 48 to 72 hours to supportive care and antibiotics. (See 'Diagnosis' above.)
●Differential diagnosis – The differential diagnosis includes severe engorgement, plugged duct, galactocele, breast abscess, and inflammatory breast cancer. (See 'Differential diagnosis' above.)
●Management
•Noninfectious – Management of noninfectious lactational mastitis consists of symptomatic treatment to reduce pain and swelling (eg, nonsteroidal inflammatory agents, cold compresses) and complete emptying of the breast via ongoing breastfeeding, pumping, and/or hand expression.
•Infectious – Management of infectious lactational mastitis includes the above measures plus administration of antibiotic therapy with activity against S. aureus. (See 'Treatment' above.)
