Breastfeeding during infancy appears to result in enhanced cognitive development during childhood, but it is not known whether breastfeeding should be encouraged for infants born small for gestational age (SGA) whose growth might otherwise benefit from nutritional supplementation. To address this issue, duration of exclusive breastfeeding and cognitive development were evaluated prospectively for 220 term children born SGA and 299 term children born appropriate for gestational age (AGA). Cognitive development was assessed using the Bayley Scale of Infant Development at 13 mo and Wechsler Preschool and Primary Scales of Intelligence at 5 y of age. Infants born SGA were given supplemental foods significantly earlier than those born AGA. Growth of infants born SGA was not related to early nutritional supplementation. The salutary effect of exclusive breastfeeding on cognitive development was greater for children born SGA than for those born AGA. Based on a linear association between duration of exclusive breastfeeding and intelligence quotient (IQ), children born SGA and exclusively breastfed for 24 wk were predicted to have an 11-point IQ advantage over those breastfed for 12 wk, as opposed to a 3-point advantage for children born AGA with similar durations of breastfeeding. The IQ distribution of children born SGA and exclusively breastfed for more than 12 wk was not different from that of all children born AGA.
Conclusion: Duration of exclusive breastfeeding has a significant impact on cognitive development without compromising growth among children born SGA. These data suggest that mothers should breastfeed exclusively for 24 wk to enhance cognitive development.