Breastfeeding in the 21st century.

Could infants born small benefit differently from supportive feeding conditions?

This letter asks whether the effects of breastfeeding should be studied specifically in babies born small for their gestational age. Its starting point is that children with restricted early growth may differ in their later feeding behavior and metabolic vulnerability, so average effects across all children may conceal differences between groups.

The authors refer to preliminary, unpublished observations from their birth cohort suggesting that longer breastfeeding was associated with fewer obesity-related behaviors in this group. The letter does not provide a full analysis of those data, and the observation should therefore be read as a reason for further study rather than as a confirmed subgroup benefit.

The broader idea is differential susceptibility. A developmental characteristic associated with greater vulnerability under difficult conditions might also be associated with greater benefit under supportive conditions. The authors propose testing whether being born small could represent this kind of environmental responsiveness, drawing an analogy with findings on genetic differences in susceptibility.

The contribution is a focused research question: which children benefit, under which circumstances, and how can support be directed accordingly? This is correspondence within a broader discussion of breastfeeding, not the main Lancet review with the same general title, and not a clinical trial establishing a different feeding recommendation for infants born small.