In this recently released article from Pediatrics, Sadaka et al have compared milestone achievement on a new Israeli evidence-based national developmental scale to the recently updated CDC milestones (10.1542/peds.2022-057499).1 The Israeli national developmental scale, the Tipat Halav Israeli Screening (“THIS”) scale, was based on over 3.5 million developmental assessments performed on more than 640,000 children and conducted during 2014-2020 by trained public health nurses; it includes 59 developmental milestones in 4 domains (gross motor, fine motor, language, and personal-social). The Israeli population is ethnically diverse, with children of Jewish (61%), Arab (21.8%), Druse (1.8%) and other ancestries, and with almost 1 in 5 mothers of children born outside Israel. THIS is used by the Israeli Ministry of Health as the official developmental surveillance protocol. In this study, the authors asked whether normative attainment ages for the updated CDC milestones were comparable to that of similar milestones on the THIS scale.
This fascinating study was made possible by the routine care, including developmental and growth assessment, vaccination and health education, provided by public health nurses in approximately 1,000 maternal child health clinics across Israel. Parents visit these clinics at 12 scheduled times between birth and age 60 months. Nurses either observed milestones in the clinic or documented per parental report. In total, 29 milestones could be compared between the CDC checklist and the THIS scale for 2 cohorts defined in the study: the NORMAL-FT cohort of 643,958 children (which excluded premature and low birth weight infants and children with abnormal growth) and the ALL-FT cohort of 758,300 children (all children excluding only those who were premature infants and those with missing data). The authors explain the process of comparison clearly, and as readers know, the CDC milestones are now calibrated to the age at which 75% of children would be expected to reach each.
I certainly expected developmental attainment on these large and recent Israeli THIS cohorts to align fully with the updated CDC milestones, and I was surprised to find that the median attainment at the CDC recommended age by the Israeli children was 96.3% for the NORMAL-FT cohort and very similar (95.2%) for the ALL-FT cohort. What does this mean? The simplest interpretation, that children living in Israel are advanced in comparison to US children, seems unlikely to explain this large a difference. The authors discuss potential reasons, including the challenges of milestone comparability, and likely more importantly, the CDC study’s use of milestone datasets from older (past 40 years), smaller, and less ethnically and culturally diverse cohorts than the comparison Israeli cohort. Does the “Flynn Effect” (a secular increase in population intelligence quotient observed throughout the 20th century)2 explain the differences given the difference in cohorts? I agree with the authors; the discrepancies they have observed and documented should not be ignored and are a potential window into research that impacts our daily practice. Topics for study include how milestones are documented, how and why these are achieved differently in different children, and whether ages of milestone attainment change over time. Practicing pediatricians will find good food for thought in this article which questions core standards we use every day in our care of children.
What is the take-home message from this study? Clearly practitioners cannot pause all developmental surveillance until new research is published that reconciles these apparently conflicting developmental rubrics! I think results from “THIS” Israeli cohort study can serve to remind us that the updated CDC milestones were not intended as a pass/fail test for children, but rather to aid in increased surveillance where needed and timely referral. We can continue to closely watch not just milestone attainment but the trajectories of our patients’ developmental progress, to listen and act on parental concerns about development, and to humbly appreciate that not all differences in development between children are fully understood. I will use “THIS” data to temper full embrace of the updated CDC milestones and as a reminder that it is these dilemmas that keep joy and mystery in the clinical practice of pediatrics.
- Zubler JM, Wiggins LD, Macias MM, Whitaker TM, Shaw JS, Squires JK, Pajek JA, Wolf RB, Slaughter KS, Broughton AS, Gerndt KL, Mlodoch BJ, Lipkin PH. Evidence-Informed Milestones for Developmental Surveillance Tools. Pediatrics. 2022 Mar 1;149(3):e2021052138. doi: 10.1542/peds.2021-052138. PMID: 35132439.
- Bratsberg B, Rogeberg O. Flynn effect and its reversal are both environmentally caused. Proc Natl Acad Sci U S A. 2018 Jun 26;115(26):6674-6678. doi: 10.1073/pnas.1718793115. Epub 2018 Jun 11. PMID: 29891660; PMCID: PMC6042097.