Type of Paper: Meta-analysis (statistical analysis and review of data from existing studies)
Purpose: To review existing studies on physical growth in international adoptees and determine the delays at adoption, the degree of catch-up after adoption, and whether physical growth is similar for height, weight, and head circumference.
- Physical growth: standard anthropometry [height, weight, head circumference (OFC)]. Z scores were taken from existing studies.
Participants: A total of 33 studies were reviewed and analyzed. The number of children included in the physical growth outcomes ranged from 527 to 3753. Average age at adoption was 30 months for studies on height, 23 months for studies on weight, and 17 months for studies on head circumference.
Methods: Meta-analysis of studies that included physical growth measures of internationally adopted children.
- There is strong evidence for serious growth delays in height, weight, and head circumference at adoption.
- Height: The average effect size in height at adoption was a delay of more than 8 cm (-2. 43 z scores) at 30 months of age.
- Children adopted under the age of 12 months had less height delay than children who were adopted at older ages.
- Longer duration of institutionalization was strongly correlated with greater delays in height at adoption.
- Weight: The average effect size in weight at adoption was a delay of 3 kg (-2. 60 z scores) at 23 months of age.
- Head Circumference: The average effect size in head circumference at adoption was a delay of -2. 39 z scores (effect size in centimeters was not reported).
- There is also strong evidence for substantial catch-up growth following adoption. The average time of follow-up in the studies was 8 years after adoption.
- There was a similar degree of catch-up for both height and weight. Although there was a large amount of catch-up for height and weight, internationally adopted children remained smaller than non-adopted peers.
- Children who were adopted after 12 months of age had greater height delays after catch-up compared to children who were adopted at younger ages.
- There was less catch-up in head circumference compared to height and weight.
- There were some regional differences in growth.
- Children adopted from South America had fewer growth delays at adoption.
- Several years after adoption, children adopted from Asia had smaller heights and weights compared to children adopted from other regions.
Conclusions & Clinical Implications: At adoption, there were large delays in all areas of physical growth (height, weight, and head circumference). Longer time spent in institutional care was associated with greater delays in height. There was significant catch-up following adoption; however, there were differences in plasticity. Catch-up in height and weight were nearly complete (i.e., similar height and weight to non-adopted peers); however, catch-up in head circumference was incomplete. Children who were adopted prior to 12 months of age had less severe height delays and better long-term outcomes in height. This finding emphasizes the importance of early intervention in these children.
Limitations of the Nutritional Results: No significant limitations.
Reference: van Ijzendoorn MH, Bakermans-Kranenburg MJ, Juffer F. Plasticity of growth in height, weight, and head circumference: meta-analytic evidence of massive catch-up after international adoption. J Dev Behav Pediatr. 2007; 28 (4): 334-343. http://www.ncbi.nlm.nih.gov/pubmed/17700087