Subclinical Mastitis in a European Multicenter Cohort: Prevalence, Impact on Human Milk (HM) Composition, and Association with Infant HM Intake and Growth

Abstract

<b>Background:</b> Subclinical mastitis (SCM) is an inflammatory condition of the mammary gland. We examined the effects of SCM on human milk (HM) composition, infant growth, and HM intake in a mother-infant cohort from seven European countries. <b>Methods:</b> HM samples were obtained from 305 mothers at 2, 17, 30, 60, 90, and 120 days postpartum. SCM status was assessed using HM Sodium (Na): Potassium (K) ratio >0.6. Levels of different macro- and micronutrients were analyzed in HM. <b>Results:</b> SCM prevalence in the first month of lactation was 35.4%. Mean gestational age at delivery was lower and birth by C-section higher in SCM mothers (<i>p</i> ≤ 0.001). HM concentrations of lactose, DHA, linolenic acid, calcium, and phosphorous (<i>p</i> < 0.05 for all) was lower, while total protein, alpha-lactalbumin, lactoferrin, albumin, arachidonic acid to DHA ratio, <i>n</i>-6 to <i>n</i>-3 ratio and minerals (iron, selenium, manganese, zinc, and copper) were higher (<i>p</i> < 0.001 for all) in mothers with SCM. There were no differences in infant growth and HM intake between non-SCM and SCM groups. <b>Conclusion:</b> We document, for the first time, in a large European standardized and longitudinal study, a high prevalence of SCM in early lactation and demonstrate that SCM is associated with significant changes in the macro- and micronutrient composition of HM. Future studies exploring the relation of SCM with breastfeeding behaviors and developmental outcomes are warranted.