Weight gain velocity in infants with achondroplasia

There are virtually no data regarding appropriate oral intake in infants with dwarfing disorders such as achondroplasia, nor is there clear information regarding appropriate weight gain velocity in this population. Yet, these individuals are at increased risk for both early failure to thrive and, later in life, for obesity. Having appropriate expectations regarding weight gain and reasonable goals in management is imperative. We sought to clarify the rate of weight gain in infants with achondroplasia during the first year of life through analysis of data from 60 infants with achondroplasia seen at least twice during the first year of life in the Midwest Regional Bone Dysplasia Clinic, University of Wisconsin-Madison between 1998 and 2018. The mean weight gain velocity during the first 3 months was 23 g/day which contrasts with 30 g/day in average statured infants. Mean weight gain from 0 to 12 months of age was 13 g/day. The 3% of weight gain velocity during the first year of life was 8 g/day, and this rate did not differ between 0-3 months and 0-12 months of age. Infants with achondroplasia slightly more than doubled their birth weights by 1 year of age in contrast to averaged statured infants who typically triple birth weights by 1 year. Infants with achondroplasia can be thriving but erroneously assessed as failing to thrive if the incorrect reference values are used. This article describes infant weight gain velocity reference data for this population.