What is the likely cause of a sore left nipple in a woman who is 35 weeks pregnant, and how should it be evaluated and managed?

Sore Left Nipple at 35 Weeks Pregnant

A sore nipple at 35 weeks pregnancy is most likely due to normal physiological changes as your breasts prepare for lactation, but you must perform a focused clinical examination to exclude infection, pregnancy-associated hyperkeratosis, or the rare possibility of pregnancy-associated breast cancer.

Most Likely Causes

Physiological Changes (Most Common)

At 35 weeks gestation (third trimester), your breasts are undergoing significant physiological changes. Prolactin levels increase during the third trimester, causing milk-producing cells to differentiate with colostrum filling the alveoli and milk ducts 1. This process commonly causes breast tenderness and nipple soreness that is typically short-lived and resolves spontaneously 2.

Pregnancy-Associated Hyperkeratosis

If the nipple appears thickened or has a rough texture, consider pregnancy-associated hyperkeratosis of the nipple. This condition:

• Affects predominantly the top of the nipple
• Is symptomatic in 68% of patients, causing tenderness, discomfort, pruritus, or sensitivity to touch
• Persists postpartum in 88% of cases 3
• Can be diagnosed clinically and confirmed histologically if needed

Infection (Less Common but Important)

Breast infection is rare during pregnancy 1. However, if present alongside redness, warmth, or fever, initiate antibiotics immediately. Any infection that does not respond to antibiotics within 48-72 hours should raise suspicion for inflammatory breast cancer 1.

Critical Red Flags Requiring Immediate Evaluation

You must actively exclude pregnancy-associated breast cancer (PABC), which can present with focal pain, nipple discharge, or skin thickening 1. While uncommon (1 per 3,000-10,000 pregnancies), PABC is increasing as women delay childbearing and represents biologically aggressive tumors 1.

Perform This Focused Examination:

• Palpate for any discrete mass (most common PABC presentation)
• Check for unilateral skin thickening, redness, or warmth
• Assess for nipple discharge - particularly single-duct bloody discharge
• Examine for axillary lymphadenopathy

Management Algorithm

If Examination is Normal (No Mass, No Discharge, No Skin Changes):

1. Reassure that physiological breast changes causing nipple soreness are common in the third trimester
2. Recommend supportive measures: well-fitting supportive bra, avoid irritating fabrics
3. Advise that symptoms typically resolve spontaneously
4. No imaging is needed for isolated nipple soreness without other findings

If Hyperkeratosis is Present (Thickened, Rough Nipple):

1. Diagnose as pregnancy-associated hyperkeratosis
2. Counsel that this persists postpartum in most cases (88%)
3. Consider topical emollients for symptomatic relief
4. Dermatology referral if severe or uncertain diagnosis 4

If Any Red Flags are Present:

1. Proceed immediately to diagnostic ultrasound (safe in pregnancy)
2. Add diagnostic mammography if ultrasound is abnormal or clinical suspicion remains high (mammography is safe during pregnancy with abdominal shielding) 1
3. Do NOT use MRI - gadolinium is contraindicated in pregnancy 1
4. Biopsy any suspicious findings - can be safely performed during pregnancy (discuss risks of milk fistula and bleeding) 1

If Signs of Infection:

1. Start oral antibiotics immediately (systemic antibiotics are superior to topical treatment) 5
2. If no response within 48-72 hours, evaluate for inflammatory breast cancer 1

Common Pitfalls to Avoid

• Do not dismiss focal unilateral nipple pain without examination - PABC can present with focal pain 1
• Do not delay imaging if clinically indicated - pregnancy is not a contraindication to mammography or ultrasound 1
• Do not assume all nipple soreness is "normal pregnancy changes" - perform a focused examination to exclude pathology
• Do not use topical antibiotics alone for infected nipples - they have poor efficacy compared to systemic antibiotics 5