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Developmental Milestones – What Does Normal Mean? :

November 14, 2019

In a recently released article in Pediatrics (10.1542/peds.2019-0374), Dr. Christopher Sheldrick and colleagues present a study that gathered and examined normative data for developmental milestones in early childhood.

In a recently released article in Pediatrics (10.1542/peds.2019-0374), Dr. Christopher Sheldrick and colleagues present a study that gathered and examined normative data for developmental milestones in early childhood. Given the central role of developmental screening in pediatric preventive health care, it is surprising that data on milestone attainment is so limited. The authors created a developmental screener, the “Survey of Wellbeing of Young Children (SWYC),” which includes questions about behavior as well as social determinants of health in addition to developmental steps. Data from over 23,000 patients who completed 41,465 screens across the 3 states of Rhode Island, Massachusetts and Minnesota were analyzed, and responses were compared to those Centers for Disease Control and Prevention (CDC) milestones with similar constructs.

The wealth of information contained in this article is a treasure trove for pediatricians. Analyses are well explained, and with the use of tests of “differential item functioning” (DIF), the authors were able to combine all of the screenings from the 3 studied states, leading to a sample that mirrors the demographics of the United States. You will also learn about “item response theory,” which enabled inclusion of results from participants with incomplete screenings. The authors conducted regression analyses to understand the relationship of milestone attainment to behavior, prematurity, race, sex, insurance type and social determinants of health. For me, the most compelling association was that of positive behavioral screening scores (i.e. behavioral difficulties) with lower developmental quotient (DQ), but other interesting associations await you. Comparison between the SWYC milestone data and the CDC milestone tracker (see the CDC app and tracker) was reassuring, in that a high proportion of children do in fact pass milestones by the age at which the CDC affirms “most children pass,” and an even higher proportion pass by the time CDC asks parents to “act early” and seek help for their child. The supplemental materials available on line for the SWYC milestones permit readers to inspect normative data by individual milestone to better understand individual item characteristics.

A fascinating aspect of this study relates to the way developmental milestone questions are asked and answered, a topic considered by the authors in the Discussion section. Tables 2 and 3 compare the CDC with the SWYC milestones’ wording, for example, “speaks unclearly” (CDC) versus “talks so other people can understand him or her most of the time” (SWYC). Would these be similarly understood by parents? Does wording makes a difference, and how differently do each of us ask about milestones? More important though, is the “grading” of milestone achievement – the SWYC response categories were “not yet,” “somewhat” and “very much.” The proportion of parents reporting milestone achievement was strikingly different when “very much” alone was compared to a category that combined “very much” and “somewhat.” What do we accept as a “pass” when we talk with parents in the office, and how does this impact our developmental assessments? This study is a “bread and butter” article for all of us who are in practice – enjoy the read!

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