Puerperal Mastitis

Mastitis is an inflammatory condition of the breast that may occur in breastfeeding women during the puerperium and is reported in women who continue to breastfeed up to 1-year after delivery. Puerperal mastitis may present as either an epidemic or sporadic (endemic) form. Epidemic mastitis occurs several days after delivery and is a hospital-acquired infection typically caused by virulent strains of Staphylococcus aureus. Infants are inoculated by personnel carrying S. aureus and transmit the bacteria to the breastfeeding mother through the nasopharynx. Improved nursery practices, including hand washing, have made epidemic mastitis a rare occurrence in developed countries. Sporadic mastitis, however, remains a relatively frequent complication of breastfeeding. Sporadic mastitis affects the periglandular connective tissue of the breast and is caused by inoculation of bacteria, either from the infant's nasopharynx or mother's skin, through cracked or fissured nipples during breastfeeding.¹

Whereas mastitis is a recognized cause of fever during the postpartum period, the precise incidence in the breastfeeding population is not well defined. Excluding the rare case of epidemic mastitis, puerperal mastitis does not present until several weeks or months after delivery and may go unrecognized by health care providers if women do not seek medical treatment. Puerperal mastitis is reported to occur in 2% to 24% of breastfeeding women from several weeks to up to 1 year after delivery in women who continue to breastfeed.^2,3,4,5,6,7 In a prospective study of 350 breastfeeding women, 83 (23.7%) developed mastitis symptoms within 1 year of delivery. Of women with mastitis symptoms, 41% presented within the first month.⁸

Risk factors for mastitis include maternal age older than 30 years,^2,4 maternal fatigue and stress,⁷ sore and cracked nipples,^2,7,8 and a history of mastitis after a previous pregnancy.^2,7 Primiparous women and women who have not breastfed in a previous pregnancy are not at an increased risk for developing mastitis.⁴ Breast engorgement, blocked lactiferous ducts, and milk stasis also contribute to the development of mastitis.

Although the exact etiology is not known, puerperal mastitis is hypothesized to occur when the offending organism gains access to breast tissue through a disruption in the skin of the nipple or areola. Bacteria then multiply within the connective tissue or duct. If the breast is not emptied properly by the nursing infant or breast pump, mastitis may develop. Mastitis also occurs in women with no evidence of nipple trauma, cracking, or fissures, so hematogenous or lymphatic spread of bacteria may contribute in some cases.

Most cases of mastitis result from infection with S. aureus.^5,9 In a series of 55 women with mastitis in whom cultures of breast milk were performed, S. aureus was isolated in 42%, coagulase-negative staphylococci in 25%, β-hemolytic streptococci in 7%, Streptococcus faecalis in 5%, Escherichia coli in 7%, and 13% of the specimens isolated other bacteria, including Enterobacter cloacae, Pseudomonas picetti, and Haemophilus influenzae.¹⁰

Puerperal mastitis classically presents with the acute onset of maternal fever (100.4°F or higher), chills, myalgia, malaise, and breast tenderness with associated erythema. Mastitis is most commonly unilateral.¹¹ On examination of the breast, the erythema is segmental, usually in the upper, outer quadrant,¹² with variable degrees of induration.⁹ A palpable, fluctuant mass should raise clinical suspicion of a breast abscess (see later), and when an abscess is suspected, a breast ultrasound should be performed immediately.

In addition, milk may be expressed from the affected breast for determination of leukocyte (normal, below 10⁶/mL) and bacterial (normal, below 10³/mL) counts.^13,14 In women with noninfectious mastitis, leukocyte counts are elevated but the bacterial counts are normal. In contrast, women with infectious mastitis have both elevated leukocyte and bacterial counts. Culture of the breast milk also may be performed to guide antibiotic therapy¹⁰; however, contamination by skin flora is difficult to avoid and may make interpretation of culture results difficult.⁹ Although susceptibility testing and guided antibiotic therapy have been reported to decrease the risk of recurrent mastitis,¹⁰ culturing the breast milk is not recommended for the diagnosis of uncomplicated mastitis.

Treatment of breastfeeding women with mastitis includes early antibiotic therapy, regular emptying of the breasts, and local comfort measures. Hospitalization for mastitis is rare.⁸

Because a high percentage of S. aureus isolates are penicillin resistant, appropriate antimicrobial agents include penicillinase-resistant penicillins¹⁰ such as dicloxacillin, amoxicillin, or nafcillin or a first-generation cephalosporin. Erythromycin or vancomycin are appropriate choices in women with a penicillin allergy. Antibiotic therapy should be continued for 10 to 14 days to avoid the development of resistant organisms.

Women with mastitis should be instructed to continue breastfeeding and consideration should be given either to increasing the frequency of feeds or manually emptying the breast between feeds.^10,12 Women should be encouraged to initiate feeds on the unaffected breast and change the infant's position at different feeds.¹³ Continued breastfeeding is not harmful to the infant,^5,9 and women who wean or decrease feeding during an episode of mastitis have an increased risk of developing a breast abscess.

Analgesics, such as ibuprofen or acetaminophen, may be taken for symptomatic relief. Increased fluid intake and adequate nutrition should be encouraged. Either cold or warm compresses may be used for comfort; however, warm compresses may aid in breast drainage.¹³ Women should continue to wear some type of nonconstricting breast support.¹⁵

Recurrent Mastitis

Of the 2% to 24% of women who have an episode of mastitis while breastfeeding, 8.5% of women have recurrent episodes.⁸ Factors increasing the risk of recurrence include resistance to the prescribed antibiotic and an inadequate course of antibiotics. Consideration may be given to culture and sensitivities of the breast milk in cases of recurrent mastitis. In addition, incorrect diagnosis should be considered along with the possibility of a carcinoma.

Breast Abscess

Breast abscess occur in up to 11%^10,16 of women with infectious mastitis. Women with noninfectious mastitis are not at an increased risk for developing an abscess. Factors contributing to the development of breast abscess include a delay in the initiation of antibiotic treatment, failure to adequately empty the breast, and cessation of breastfeeding during an episode of mastitis. Breast ultrasound is accurate in the diagnosis of an abscess.¹⁷ Surgical incision and drainage is required for treatment. During surgery, all loculations should be disrupted and biopsy of the abscess wall should be considered to rule out a rare case of carcinoma.^11,18 Antibiotic therapy should be continued. An acute breast abscess associated with pregnancy usually resolves rapidly with appropriate treatment.