Does weaning influence growth and health up to 18 months?

Background: National and international recommendations for the age of introducing solid foods (weaning) are founded on insufficient evidence and little is known about the short and medium term consequences associated with early or late weaning. Aims and Methods: Data from over 1600 infants from five prospective randomised trials conducted in the UK between 1993 and 1997 were used to determine the influence of weaning less than or equal to 12 weeks or > 12 weeks on growth and health outcomes (diarrhoea and vomiting, lower respiratory chest infections, atopy, sleep patterns) up to 18 months post-term, in term appropriate for gestational age (AGA), term small for gestational age (SGA), and preterm infants. Results: Term infants weaned less than or equal to 12 weeks were heavier at 12 weeks of age than those weaned after 12 weeks, but showed slower gain in weight, length, and head circumference between 12 weeks and 18 months than those weaned after 12 weeks; by 18 months, there were no significant differences in size between the two groups. A similar pattern was seen in preterm infants. Breast fed term infants were more likely to be sleeping though the night at 9 months if they were weaned before 12 weeks. No weaning effects or interactions were observed for health outcomes. Conclusions: We found little evidence that weaning before or after 12 weeks influences health outcomes up to 18 months. Early weaned infants were larger at 12 weeks than later weaned infants but the growth trajectories of the two groups "converged'' by 18 months. These findings do not exclude the later emergence of programmed effects of weaning practices.