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

Abstract

Background: 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. Methods: 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. Results: 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 (p ≤ 0.001). HM concentrations of lactose, DHA, linolenic acid, calcium, and phosphorous (p < 0.05 for all) was lower, while total protein, alpha-lactalbumin, lactoferrin, albumin, arachidonic acid to DHA ratio, n-6 to n-3 ratio and minerals (iron, selenium, manganese, zinc, and copper) were higher (p < 0.001 for all) in mothers with SCM. There were no differences in infant growth and HM intake between non-SCM and SCM groups. Conclusion: 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.

Infant Anthropometry and Growth Velocity Before 6 Months are Associated with Breastfeeding Practices and the Presence of Subclinical Mastitis and Maternal Intestinal Protozoa in Indigenous Communities in Guatemala

“…On the one hand, a higher milk Na:K ratio was negatively associated with HCAZ attainment in early lactation. This finding is similar to previous research in Guatemala ( 29 ) and globally, which has shown a negative trend between SCM and head circumference ( 12 , 13 ). On the other hand, higher milk IL-8 was positively associated with HCAZ attainment in established lactation.…”

“…Our study also found that a higher milk Na:K ratio, consistent with SCM, increased the odds of being underweight in early lactation. This finding confirms previous work in Bangledesh ( 8 ), Zimbabwe ( 9 ), Zambia ( 10 , 11 ), and most recently Europe ( 13 ), where SCM has been associated with reduced infant weight. On the one hand, SCM might lower milk volume, although previous research found that milk intake among infants did not differ for mothers with SCM ( 12 ).…”

“…On the one hand, SCM might lower milk volume, although previous research found that milk intake among infants did not differ for mothers with SCM ( 12 ). On the other hand, SCM has been shown to alter milk nutrient ( 13 , 15 ) composition and younger infants might thus be more susceptible to these compositional changes.…”

“…The concentrations of 4 proinflammatory cytokines, IL-1β, IL-6, IL-8, and TNF-α, were measured using the MILLIPLEX MAP Human high-sensitivity T-cell magnetic bead panel (HSTCMAG-28SK; EMD Millipore) as previously described ( 30 ). SCM is a common, asymptomatic inflammatory condition, where cytokines are transiently released by mammary gland epithelial and immune cells into milk, enhancing permeability and altering milk composition ( 13 , 14 ). Milk proinflammatory cytokines (continuous variables) were used as indicators of breast inflammation.…”

“…In Ghana, a study of 60 lactating mother-infant dyads between 3 and 6 mo postpartum found that mothers with SCM had infants with lower length, and a nonstatistical trend was also observed for lower infant weight and lower infant head circumference ( 12 ). A European study reported that infants born to mothers with SCM had smaller head circumferences, lower weight, lower weight-for-length z -score (WLZ), and lower BMI, but that differences disappeared as lactation progressed from 2 to 120 d postpartum ( 13 ).…”