Subclinical mastitis may not reduce breastmilk intake during established lactation

Objective: This study determined the effect of subclinical mastitis (SCM) on infant breastmilk intake. Design: Participants (60 Ghanaian lactating mothers and their infants) were from periurban communities in the Manya Krobo district of Ghana in 2006-2007. Bilateral breastmilk samples were obtained once between months 3 and 6 postpartum and tested for SCM using the California mastitis test (CMT) and the sodium/potassium (Na/K) ratio. Infants' 12-hour breastmilk intake was assessed by test weighing. CMT scoring for SCM diagnosis was scaled as ≥1 = positive (n = 37) and <1 = negative (n = 23). SCM diagnosis was confirmed as a Na/K ratio of >1.0 (n = 14). Results: Breastmilk intake was nonsignificantly lower among infants whose mothers had elevated Na/K ratios of >1.0 (-65.1 g; 95 confidence interval -141.3 g, 11.1 g). Infants whose mothers were positive for SCM with both CMT and Na/K ratio criteria had significantly lower breastmilk intake (-88.9 g; 95 confidence interval -171.1 g, -6.9 g) compared to those whose mothers tested either negative with both tests or positive on only one. Infant weight (p < 0.01) and frequency of feeding (p = 0.01) were independently associated with breastmilk intake. However, the effect of SCM on breastmilk intake disappeared when infant weight and feeding frequency were included in a multiple linear regression model. Conclusions: The results of this study did not show an effect of SCM on breastmilk intake among 3-6-month-old infants. A larger sample size with a longitudinal design will be needed in future studies.