Weight reference charts for British long-term breastfed infants

Aim: To produce a modification of the British 1990 weight reference reflecting the growth of long-term breastfed infants. Methods: 120 infants from the Cambridge Infant Growth Study fed breast milk (with no formula) for at least 24 wk, with solids introduced at a mean age of 15 wk, were weighed every 4 wk from birth to 52 wk. Weights were converted to standard deviation scores (SDS) for gender and age post-term based on the revised British 1990 reference, averaged and smoothed across age, and then converted back to weights to provide modified median weight curves by gender. Other centile curves were constructed assuming the same variability and skewness by age as for the British reference. Results: Long-term breastfed infants were slightly heavier than the reference at birth and crossed centiles upwards to reach +0.3 SDS at 2 mo, but subsequently crossed centiles downwards to −0.2 SDS by 12 mo. Conclusion: The British 1990 reference, although better than previous growth standards, reflects the growth of long-term breastfed infants only imperfectly, with mean weight falling by 0.5 SDS from 2 to 12 mo. The provision of breastfeeding-specific centiles, either as a transparent overlay or as an alternative chart, should be useful for professionals and parents to monitor the weight of long-term breastfed infants.