The Developmental Milestones questions include indicators of fine and gross motor, language, social, and cognitive development. Items were chosen based on a review of a large number of instruments as well as consultations with experts in the field. Based on clinical experience, we observed that parents often describe behaviors that approximate a given milestone before their child manifests the full behavior. To reflect this, we adopted a prototypical scoring systems with three response options where 0 = not yet; 1 = somewhat, and 2 = very much.

The validity of the Developmental Milestones was assessed via comparison with: (a) the Ages & Stages Questionnaire, 3rd Edition (ASQ-3), a 30-item developmental screening instrument, and (b) previous diagnoses of developmental delay as indicated by parent report. While the finalized set of Developmental Milestones is still in development, initial data are encouraging. Overall, the Developmental Milestones predicts clinical ASQ-3 scores with sensitivity of .81 and specificity of .76 and parent report of diagnoses with sensitivity of .78 and specificity of .73. A study designed to replicate these results is ongoing.

Our research found that the 2- and 60-month forms have less robust validation data to support their use for scoring as compared to the other age forms. Hence, we urge caution in interpreting total scores for the 2-month and 60-month forms. They are useful for surveillance, but the scores should be considered imprecise. For this reason, we excluded these forms from our primary scoring table (see Milestones Scoring Guide).