Incidence of and Risk Factors for Lactational Mastitis: A Systematic Review.
Emily Wilson, Susannah L Woodd, Lenka Benova
PMID 32286139WHAT IT FOUND
Lactational mastitis is common, affecting roughly one in four women breastfeeding up to 25 weeks postpartum in high-income settings.
Cracked nipples, blocked ducts, and prior mastitis are consistently linked to higher risk, but no intervention is proven to prevent it.
Key findings
01The pooled incidence rate of lactational mastitis was 11.1 episodes per 1,000 breastfeeding weeks between birth and 25 weeks postpartum, though heterogeneity between studies was very high.
02Cracked nipples were significantly associated with lactational mastitis in all eight studies that investigated this specific link.
03Women who had mastitis during previous lactations were significantly more likely to experience it again, with risk estimates ranging from 74% more likely to four times more likely.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
No systematic quality assessment of included studies was conducted. High heterogeneity in the meta-analysis (I² = 98%) means the pooled incidence estimate should be interpreted with caution. Most studies relied on self-reported data, which is susceptible to recall bias, particularly for the timing of risk factors like blocked ducts. There is no globally accepted clinical definition of mastitis, so studies used varying criteria. The review is heavily skewed towards high-income countries; only three studies were from low-income settings, limiting generalizability to those contexts. Many risk factor associations are based on poorly designed or unadjusted analyses, making causal inference difficult.
Declared interests
The authors declared no potential conflicts of interest and received no financial support for the research.
The easy way to misread this
Do not interpret the association between nipple shields, creams, or pumps and mastitis as evidence that these products cause the condition. The review notes that reverse causality is likely, as women often use these products to manage existing nipple damage or pain, which are themselves risk factors.