Lactation, breastfeeding and mastitis

• Lactation is a supply-and-demand system: the breast makes milk in response to regular, effective removal by a baby or a pump, and oxytocin drives the let-down that moves it out. ^[10]
• WHO and UNICEF recommend that babies start breastfeeding within the first hour after birth, are exclusively breastfed for the first 6 months, and continue breastfeeding with complementary foods for 2 years or beyond. ^[1]
• Benefits are broad, so contraindications are few; the commonest true contraindications are infant galactosaemia, untreated maternal HIV in settings where safe replacement feeding is available, and a small group of medicines such as anticancer drugs and lithium. ^[5][3][9]
• Most medicines are compatible with breastfeeding, because the dose the baby receives in milk is usually small, but every drug should be checked in a current lactation reference before it is prescribed. ^[9]
• Mastitis starts with milk stasis and inflammation, with or without infection; supportive care and, if needed, anti-staphylococcal antibiotics for 10 to 14 days are standard, and breastfeeding should continue. ^[8][10][11]
• A breast abscess complicates 3 to 11% of lactational mastitis and needs drainage; red flags for sepsis or skin necrosis mean hospital admission. ^[8][11]

By the end of this page you should be able to:

1. Explain how prolactin and oxytocin control milk production, let-down and the feedback that matches supply to demand.
2. State the WHO/UNICEF recommendations on initiation, exclusivity and duration, and describe the health benefits for the baby and for the woman.
3. Recognise the few genuine contraindications to breastfeeding and how feeding is handled in maternal HIV.
4. Assess a woman's medicine list safely during breastfeeding, using lactation-specific resources.
5. Describe the mastitis spectrum, tell mastitis from blocked duct, engorgement, abscess and inflammatory breast cancer, and order the right investigations with their thresholds.
6. Treat lactational mastitis and breast abscess along current guidelines, including antibiotic choice and duration, and say when to refer or admit.
7. Plan practical breastfeeding support in hospital and community, and outline low-resource care.

Lactation is best understood as a cycle. The breast prepares in pregnancy (mammogenesis), switches on milk secretion after delivery (lactogenesis), keeps producing once feeding is established (galactopoiesis), and gradually closes down after weaning (involution). ^[10] Engorgement, a blocked duct, inflammatory mastitis, bacterial mastitis, phlegmon, abscess and galactocele are points along one spectrum of duct inflammation, stasis and, sometimes, infection. ^[8]

Possible difficulties are best classified by the dominant mechanism:

Fewer than half of infants under 6 months old are exclusively breastfed worldwide, against the WHO/UNICEF aim of at least 50% by 2025. ^[1] WHO and UNICEF recommend that children initiate breastfeeding within the first hour of birth, are exclusively breastfed for the first 6 months, and continue breastfeeding with complementary foods to 2 years or beyond. ^[1]

Breastfeeding is much commoner than is realised: the main change world-wide is that a minority of families achieve exclusivity for 6 months. ^[1] Interruption of lactation at population level is associated with higher maternal risks of breast cancer, ovarian cancer, diabetes, hypertension and heart disease, and higher infant risks of infectious disease, sudden infant death syndrome and metabolic disease. ^[5]

Mastitis is a frequent complication: reported incidence ranges widely, from up to 3% of breastfeeding women in older series to 1% to as high as 33% globally in recent reviews (about 7% and 10% in older US series). ^[10][8] A breast abscess complicates 3 to 11% of lactational mastitis. ^[8] These conditions are usually manageable, but they remain a common reason for premature cessation of breastfeeding. ^[10]

For breastfeeding success, the main risk is not biology but lack of support: poor latch, infrequent or ineffective drainage, hyperlactation, nipple fissure, engorgement, maternal fatigue, stress and poor continuity of carer are the common precipitants of difficulty and mastitis. ^[4][10] A shallow latch and infrequent feeds cause milk stasis, so the first intervention is almost always to improve drainage and attachment rather than to add medicines. ^[10]

Specific named risk factors supported by the sources include:

• Excessive or prolonged nursing, which can produce nipple fissures and mastitis. ^[10]
• Inefficient milk removal from poor technique, which the WHO mastitis review identifies as an important underlying cause. ^[2]
• Milk stasis itself, which is the usual trigger for lactational mastitis. ^[8]
• Formula supplementation or separation of mother and baby, which interrupt supply and demand. ^[1][5]

Low mood, pain and exhaustion operate through the same final pathway: high catecholamine levels suppress oxytocin and vasoconstrict the mammary circulation, so a distressed mother can have a normal mechanism that is temporarily blocked. ^[10]

The GLOWM chapter traces lactation through four linked stages. ^[10] In pregnancy the breast grows (mammogenesis) under rising oestrogen, progesterone and prolactin, and colostrum, the first milk, appears by the second trimester. ^[10] At delivery the placenta is lost, progesterone falls abruptly and the inhibition it exerts on milk secretion is lifted; secretory activation (lactogenesis II) then begins within 24 to 72 hours, although complete secretory maturation takes 2 to 5 days. ^[12][10] Once feeding is established, galactopoiesis is driven by autocrine control: regular suckling raises prolactin and oxytocin; the breast's capacity to store milk ranges from 80 to 600 ml and varies between women, with more rapid synthesis when capacity is smaller, and the alveolar feedback inhibitor of lactation (FIL) accumulates if removal stalls. ^[10][12] Involution after weaning takes roughly 3 months. ^[10]

Two hormones do the work. Prolactin binds alveolar epithelial cells, drives milk protein synthesis through messenger RNA, and suppresses GnRH, producing lactational amenorrhoea. ^[10] If a woman is fully breastfeeding and remains amenorrhoeic, up to 98% have protection from pregnancy for 6 months after delivery. ^[10] Oxytocin causes myoepithelial contraction and release of milk into the ducts (the let-down), and it becomes a conditioned response to seeing or hearing the baby. ^[10] Oxytocin, not prolactin, is the hormone that stress blocks, which is why anxiety delays let-down while supply continues for a while. ^[10]

Milk composition changes with time. Colostrum, the first milk, is small in volume and rich in immunoglobulin A, lactoferrin and cells, and is the infant's first feed after birth. ^[10] By the end of the second week output rises from 100 to about 500 ml per day. ^[10] A normal mature milk supply is supported by adequate maternal nutrition, with extra protein, calcium, iron and vitamin A. ^[10]

Mastitis classically follows milk stasis. Duct narrowing from oedema and engorgement raises intraductal pressure, flushes the breast poorly, and allows a secondary bacterial infection, most often by penicillin-resistant Staphylococcus aureus entering through a nipple fissure. ^[8][10] Hyperlactation can worsen duct narrowing. ^[8] HIV is a special case: mastitis increases HIV shedding in breast milk, which is why adherence to antiretroviral therapy matters so much in a breastfeeding woman with HIV. ^[2][3]

Mastitis usually presents with a red, hot, painful area in one breast, often wedge-shaped, sometimes with localised swelling and systemic symptoms. ^[8] Fever of 38 C or higher, tachycardia, chills, myalgias and malaise define the systemic end of the spectrum. ^[8] A blocked duct is the milder cousin: a tender, palpable lump or wedge of fullness without fever. ^[10] Engorgement is diffuse and bilateral, usually at days 3 to 4, and improves with drainage. ^[10]

On examination, look for a wedge of erythema, tenderness and oedema, check the nipple for fissure or bleb, assess attachment if the baby is present, and feel for a focal fluctuant collection that would indicate an abscess. ^[8][10] NICE reminds clinicians that nipple and breast discomfort and symptoms of inflammation are routine checks at every postnatal midwife contact, and that worsening redness and swelling persisting more than 24 hours despite self-care may indicate mastitis. ^[4]

A galactocele feels like a smooth, non-tender, milk-filled cyst without erythema. ^[10] Inflammatory breast cancer is the condition most often confused with mastitis in the non-lactating woman; it is suggested by peau d'orange, non-resolution, and absence of improvement with lactation-specific care, and it requires imaging and biopsy.

Use the table above for the main comparisons. The crucial distinction is not mastitis versus abscess, which ultrasound settles, but mastitis versus inflammatory carcinoma, which history and failure to resolve settle. Any redness that does not settle within the expected course, any non-lactating breast, or any woman over 35 with a new inflammatory change needs imaging and biopsy rather than another antibiotic course.

Most mastitis is a clinical diagnosis. The investigations that matter, with their working thresholds, are:

There is no formal scoring system for mastitis. Severity is best described clinically as local inflammation, systemic illness or abscess, and that description drives management. Red flags that change the level of care are:

• signs of sepsis, threatened or actual skin necrosis, spreading cellulitis, diabetes, immunosuppression or known or suspected MRSA, which require admission and surgical assessment. ^[11]
• a fluctuant focal collection, indicating abscess, which needs drainage. ^[11]
• RCOG's reminder that mastitis is easily overlooked and may lead to breast abscess, necrotising fasciitis or toxic shock syndrome; two women died of mastitis-related sepsis in the 2005 to 2008 period reported. ^[7]

The following flowchart sets out the standard approach used by recent mastitis pathways, including the NHS Highland guideline, with WHO, NICE, ACOG and RCOG principles applied. ^{[1][4][5][7][11]}

• Continue breastfeeding or express regularly. WHO and GLOWM both stress that the woman should keep feeding, because stopping increases the risk of abscess. ^[2][10]
• Advise rest, adequate fluids and simple analgesia. ^[4][10]
• Use a warm or cool compress for comfort and to support flow; the NHS Highland guideline allows either, but warns against excessive heat. ^[11] Older teaching favoured heat before feeds for a blocked duct. ^[10]
• Avoid deep, vigorous massage. Firm, painful pressure can worsen inflammation; gentle pressure or light massage over a plugged duct is preferred. ^[8]
• Optimise attachment and feeding position, since correcting drainage is the core treatment. ^[4][10]
• If the baby cannot attach, express at least 8 times in 24 hours. ^[11]
• Review early. The NHS Highland pathway uses 12 to 24 hour reassessment to decide on antibiotics. ^[11]

Antibiotics are reserved for systemic illness, or for cases that do not improve after 12 to 24 hours of good supportive care. ^[11]

Durations differ by source: NHS Highland recommends 10 to 14 days for mastitis and 7 to 10 days for abscess with drainage, whereas the GLOWM chapter recommends 7 to 10 days for systemic mastitis. ^[11][10]

RCOG's sepsis guideline reminds us that mastitis may lead to abscess, necrotising fasciitis and toxic shock syndrome, and that maternal deaths have occurred from mastitis-related sepsis. ^[7] Suspected sepsis means admission and IV therapy, not another oral prescription.

• First-line treatment is percutaneous aspiration, usually ultrasound-guided, with a needle of 21 gauge or larger, sending aspirate for culture and sensitivity, plus antibiotics. ^[11]
• Incision and drainage under general anaesthesia is reserved for skin necrosis, a large or deep collection, or failed aspiration. ^[11]
• Even with an abscess, many women can continue breastfeeding from both breasts. ^[10]

• Reassess within 24 to 48 hours during acute treatment. ^[11]
• If there is no improvement, request a breast ultrasound for a deeper collection and discuss with breast surgery or breast radiology. ^[11]
• Refer the same day for sepsis, skin necrosis, spreading cellulitis, immunosuppression or diabetes. ^[11]
• Refer any atypical feature, non-lactation-related change or non-resolving erythema for triple assessment to exclude malignancy.

• Breast abscess in 3 to 11% of lactational mastitis. ^[8]
• Recurrent mastitis and abscess, which raise the possibility of resistant organisms such as PVL-producing or MRSA strains, particularly after a caesarean or recent nursery exposure. ^[7]
• Necrotising fasciitis and toxic shock syndrome, rare but life-threatening. ^[7]
• Early weaning and maternal distress, because pain and fear stop feeding.
• Milk fistula after drainage, usually closing spontaneously with continued breastfeeding.
• Increased HIV shedding in breast milk when mastitis occurs in an HIV-positive woman. ^[2]

Most cases settle within 24 to 48 hours of good supportive care, with or without antibiotics, and the woman returns to full feeding. ^[8][10][11] An abscess needs drainage but usually heals completely, and breastfeeding can continue throughout. ^[10] Recurrence is a signal to review technique, hyperlactation, smoking and local resistance.

• Antenatal education about the benefits of feeding, positioning and attachment. ^[4][5]
• Baby-friendly hospital measures such as a written breastfeeding policy, staff training, skin-to-skin contact, rooming-in, exclusive breastfeeding unless medically indicated, feeding on demand, avoiding pacifiers and bottles, and referral to support groups on discharge. ^[5]
• Early postnatal face-to-face breastfeeding support that continues until feeding is established and problems are resolved. ^[4]
• First feed within the first hour after birth, or as soon as mother and baby are ready. ^[1][5]
• Basic hygiene: a well-fitting but not restrictive bra, clean hands for expressing milk, and prompt attention to nipple pain or cracks. ^[10]
• Vitamin D supplementation for the breastfeeding woman is recommended by NICE; follow national dose guidance. ^[4]
• Smoking cessation, because heavy smoking reduces and contaminates milk. ^[10]

WHO's 2016-updated guidance is that mothers living with HIV who are on ART and adherent should breastfeed exclusively for the first 6 months and continue with complementary feeding until 12 months, and may continue to 24 months or beyond, because ART is effective at preventing postnatal transmission. ^[3] Countries choose whether to promote breastfeeding with ART, or to provide replacement feeding where it is acceptable, feasible, affordable, sustainable and safe. ^[3] Mothers can be reassured that shorter breastfeeding, even mixed feeding, is better than none if circumstances make exclusive feeding impossible. ^[3] Because mastitis raises HIV shedding, any redness must be treated promptly and ART adherence reinforced. ^[2][3]

Most medicines are compatible with breastfeeding; the dose in milk is usually small and well below the doses given directly to neonates. ^[9] ACOG states that contraindications to breastfeeding are few and most medications and vaccinations are safe, with exceptions. ^[5] Drugs contraindicated during breastfeeding include anticancer drugs, lithium, oral retinoids, iodine, amiodarone and gold salts. ^[9] Breastfeeding is not recommended for a woman receiving radioactive isotopes or chemotherapy. ^[10] Alcohol passes into milk in the same concentration as maternal blood and can sedate or impair the infant's motor function. ^[10] Lithium can produce infant toxicity. ^[9][10] Heavy smoking is contraindicated because nicotine reduces prolactin and appears in milk. ^[10] Contraception should usually be progesterone-only once lactation is established; low-dose combined oral contraceptives have a limited effect on milk volume once lactation is established, but progesterone-only options are preferred. ^[10] When medication is essential, use the lowest effective dose, time doses after feeds where pharmacokinetics allow, and check a current lactation reference such as LactMed, BNF-style guidance or a national medicines information service rather than an old summary. ^[9][4] Medications used to induce lactation, such as metoclopramide and chlorpromazine, have occasionally been used for surrogacy or relactation when breast growth and stimulation have prepared the breast; in practice this is specialist care. ^[10] Anticoagulants merit a note: heparin and warfarin are unlikely to cause bleeding in a breastfed infant because of high molecular weight and protein binding, but any decision must be checked against current guidance. ^[10]

Inflammatory mastitis occurring outside lactation, or a new breast change in an older woman that does not resolve within the expected timeframe, must be assessed for underlying malignancy with imaging and biopsy rather than treated as infection.

Relactation is possible when feeding has stopped, and induced lactation for an adopted baby may succeed with weeks of breast stimulation, a galactagogue in selected cases, and supplementing to meet the baby's needs. ^[10]

• The most valuable diagnostic tool is the mother's history and a trained clinical examination; a wedge of erythema after a recent change in feeding is usually mastitis.
• Supportive care, continued feeding and oral antibiotics are sufficient for most cases.
• If no ultrasound is available, attempt free-hand needle aspiration only if clinical skill and sterile equipment are available; otherwise refer.
• Support early referral for any sepsis or skin necrosis.
• If milk cannot be preserved or stored, prioritise direct breastfeeding and maternal nutrition, because human milk is safer than formula prepared without clean water. ^[1]

• Lactation is supply-and-demand driven by prolactin synthesis and oxytocin let-down; regular, effective removal is the single most important determinant of supply. ^[10]
• WHO and UNICEF recommend breastfeeding within the first hour, exclusivity for 6 months, and continued breastfeeding with complementary foods to 2 years or beyond. ^[1]
• Interrupting lactation adversely affects maternal risks of breast, ovarian, metabolic and cardiovascular disease and infant risks of infection, sudden infant death syndrome and metabolic disease. ^[5]
• Contraindications to breastfeeding are few; most medications are compatible because the dose in milk is small. ^[5][9]
• Drugs that are contraindicated include anticancer drugs, lithium, oral retinoids, iodine, amiodarone, gold salts, radioactive isotopes and chemotherapy. ^[9][10]
• Reported mastitis incidence varies widely (from up to 3% in older series to 1% to 33% globally in recent reviews, about 7% and 10% in older US series); treatment is by improving drainage and, when systemic or persistent, by anti-staphylococcal antibiotics for 10 to 14 days (some older texts use 7 to 10 days for systemic mastitis). ^[8][10][11]
• Flucloxacillin 500 mg four times daily for 10 to 14 days is a typical oral regimen, with clindamycin for penicillin allergy. ^[11]
• A breast abscess complicates 3 to 11% of lactational mastitis and requires drainage, usually by ultrasound-guided aspiration. ^[8][11]
• Do not stop breastfeeding abruptly unless there is a true contraindication; stopping worsens mastitis and increases the risk of abscess. ^[2][10]
• Red flags are sepsis, skin necrosis, spreading cellulitis, immunosuppression, diabetes and suspected MRSA, which need admission and IV therapy. ^[7][11]
• Breastfeeding women should receive consistent face-to-face support, including observation of a feed within the first 24 hours and again in the first week, and safe medicines advice. ^[4]
• In HIV, mothers on adherent ART can breastfeed exclusively for 6 months and continue to 12 months or beyond, because ART markedly reduces transmission; mastitis worsens shedding. ^[3]

No existing MedGrasp links are added, because none is verified as a dependency here; the closely related material is infant feeding and colic, breast disease including breast cancer, contraceptive methods in the postpartum period, and HIV infection.