Abstract
Dear Editor:
B
Thirty-nine adolescent (16±1 years old) and 26 adult (20±4 years old) healthy primiparous volunteers were invited to participate during a period of 4 months. All mothers were recruited within the first 5 days postpartum. Inclusion criteria for volunteers were as follows: nonsmokers, residence in the Quito metropolitan area, normal singleton pregnancy and vaginal delivery of the child, at-term parturition, and maternal willingness to exclusively breastfeed the child for the duration of the study.
Colostrum, transition milk, and mature milk were obtained in the morning after an overnight fasting period of 8–10 hours. Concentrations of IL-6 and TNF were measured by chemiluminescence, and IgA2 levels were assessed by immunoturbidimetry. To establish differences within and between groups, paired Wilcoxon signed ranks test and the Mann–Whitney U test were used.
Three important immune components were chosen to compare breastmilk from adolescent and adult mothers: IgA, the most important mucosal antibody protecting against infection, and two immune-modulatory cytokines, IL-6 and TNF. IgA levels were found to be highest in colostrum in both adolescent and adult mothers, with similar levels recorded in both groups (Table 1). Levels of the cytokines IL-6 and TNF were also highest in colostrum and decreased sequentially in transition and mature milk (Table 1). Although the overall trend of production of these immune components was similar between the two groups of mothers, adolescent mothers showed a significantly higher TNF levels in transition milk and mature milk compared with adult mothers (Table 1). Taken together, these data indicate that breastmilk undergoes notable changes in immune component levels as lactation progresses and that adolescent mothers secrete more TNF in their milk during the majority of the lactation period.
Colostrum (C), transition milk (TM), and mature milk (MM) were sampled in the morning after an overnight fasting period. Concentrations of interleukin-6 (IL-6) and tumor necrosis factor (TNF) were measured by chemiluminescence, and immunoglobulin A2 (IgA2) levels were assessed by immunoturbidimetry; samples were measured in duplicates. Data are median±interquartile range values.
p<0.05 within groups; bp<0.008, cp<0.014 between groups.
BDL, below detection limit; NA, not applicable.
To our knowledge, this is the first study to specifically address levels of IgA2, IL-6, and TNF in the milk of adolescent mothers and to compare them with adult mothers in the same population. In order to maximize the power to discern differences in our small study population, we applied strict inclusion and exclusion criteria to carefully control for possible demographic and health factors that could influence results and applied a consistent milk collection protocol for all mothers. By comparing a homogeneous population of women differing only in their age, this study suggests that healthy mothers who undergo a normal pregnancy and vaginal birth for their first child show an important difference in the TNF levels in their breastmilk when they are under 19 years of age. Potential limitations of the present work include the limited number of subjects included in the study as well as the use of one sample from colostrum, transition, and mature milk. The difficulty in obtaining milk samples and the cost of the analysis precluded us from carrying out a more ample analysis. However, the reproducibility of the data and similar trends in the studied groups show representative differences within and between groups.
In conclusion, there are important differences in breastmilk composition between adolescent and adult breastfeeding mothers. Our work supports the idea that the young age of teen mothers affects the immune composition of breastmilk. We propose that the state of development of epithelial cells in the mammary gland may affect the concentrations of IgA2, IL-6, and TNF, which consequently may influence further mammary tissue development and infant immune system development. This study suggests that large-scale clinical studies and investigation of the molecular mechanisms of mammary development are important for understanding and promoting the maximal health of infants born to adolescent mothers.