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Rapid Infant Weight Gain: What Should Practitioners Know?

April 5, 2023

In a recently released study in Pediatrics, “Maternal BMI, Rapid Weight Gain, and Child Size,” Dr. Stephanie Gilley and collaborators from the University of Colorado School of Medicine asked whether maternal pre-pregnancy BMI (body mass index) and infant rapid weight gain interact to additively increase risk for childhood obesity (10.1542/peds.2022-059244). The authors note that maternal obesity and infant rapid weight gain are each well known to be associated with risk for offspring obesity and overweight; their research question was whether infant rapid weight gain (RWG) and maternal pre-pregnancy BMI (ppBMI) work jointly to augment risk of childhood obesity. The question is highly relevant to preventive health care in the first year of life – how important is it for practitioners to identify interventions to mitigate RWG? Infant feeding advice is a core part of well care visits, yet influencing this highly personal aspect of parenting is not simple; if we are to intervene it needs to be for a really good reason.

Study participants were recruited from a longitudinal observational study, The Healthy Start Study, in which 1,410 pregnant women were enrolled before the 24th week of gestation. In-person visits occurred during pregnancy, at birth, during infancy (median 5 months of age), and in early childhood (median 5 years of age). Of these, 414 participants with complete data as relevant for this analysis, could be included. In this cohort, 77 (18.6%) of infants experienced RWG, defined as an increase in weight-for-age Z score of >0.67 from the birth visit to the infancy visit (a cut-off previously correlated with childhood obesity risk). Pre-pregnancy BMI was classified as overweight or obese in similar proportions (50.7% and 49.6%, respectively) in both the RWG and the normal weight gain infant cohorts. 

I will cut to the chase for the sake of brevity here, but there is so much more to learn from this article! Both ppBMI and RWG individually were, expectedly, associated with childhood obesity in both boys and girls, determined using the Centers for Disease Control and Prevention 2000 growth charts, at the mean childhood visit age of 4.7 years. But for girls, RWG significantly modified the association between ppBMI and early childhood BMI Z-scores, while among boys, RWG did not significantly modify this association. These sex differences remain unexplained, though the authors note that hormonal differences in infancy may play a role. Interestingly neither breastfeeding status at the time of the infancy visit nor childhood daily calorie intake changed these associations. There is much more to read, and I hope you will dive into this well-done study.

But where does this leave practitioners? Certainly, additional research is needed, and indeed the authors emphasize this point. But my own clinical take home message is that RWG is very important and deserves my attention and thoughtful discussion with parents. We may not yet have an evidence-based intervention to prevent RWG, but until then, I am hopeful that parental awareness can lead to small changes that make a big difference for a child’s future health.

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