Developmental milestones norms are widely used worldwide and are fundamental for early childhood developmental surveillance. We compared a new Israeli evidence-based national developmental scale with the recently updated Centers for Disease Control and Prevention (CDC) checklists.
We used a cohort of nearly 4.5 million developmental assessments of 758 300 full-term born children aged 0 to 6 years (ALL-FT cohort), who visited maternal child health clinics in Israel for routine developmental surveillance. Among the assessed milestones of 4 developmental domains (gross motor, fine motor, language, and personal–social) we identified milestones that had equivalents on the CDC checklists and assessed the attainment rates of the Israeli children at the ages recommended by the CDC, at which ≥75% of the children would be expected to achieve the milestone. The analysis was repeated on a subgroup of 658 958 children who were considered healthy, typically developing by their birth and growth characteristics (NORMAL-FT cohort).
There were 29 milestones, across all developmental domains and assessment ages, whose definitions by both tools were compatible, and could be compared. The attainment rate at the CDC-recommended age was >90% for 22 (76%) and 23 (79%) milestones, and the median attainment rates were 95.2% and 96.3% in the ALL-FT and NORMAL-FT cohorts, respectively.
For almost all comparable milestones of all domains and all ages, children of the Israeli cohorts achieved the milestones earlier than expected by the CDC-defined threshold age. Evidence-based analysis of milestone norms among different populations may enable adjustments of developmental scales and facilitate more personalized developmental surveillance.
New evidence-informed milestones for developmental surveillance have been recently published, updating the Centers for Disease Control and Prevention checklists on the basis of a broad literature search, parent resources, professional teaching resources, and commonly used screening and diagnostic evaluation tools.
Analysis of the normative attainment age suggested by the updated Centers for Disease Control and Prevention checklists using the actual attainment rate of compatible milestones from a large cohort of nearly 4.5 million assessments of >750 000 Israeli children aged 0 to 6 years.
Routine early childhood developmental surveillance using norms of milestones attainment is fundamental for the early identification of children at risk for developmental delay, allowing timely intervention.1–11 However, unlike screening and diagnostic tools, milestone norms lack strong evidence-based validation and are often inconsistent across studies.12,13 The Centers for Disease Control and Prevention (CDC) partnered with the American Academy of Pediatrics to convene a panel of subject matter experts to identify a set of evidence-informed milestones for revision of the Learn the Signs and Act Early materials, commonly used for the practice of developmental surveillance. On the basis of a broad literature search, parent resources, professional teaching resources, and commonly used screening and diagnostic evaluation tools, new evidence-informed millstones for developmental surveillance have been recently published, updating the milestones in the CDC checklists.14 In this developmental surveillance tool, ?80% of the final milestones had normative data from 1 or more sources.
In a newly published study, we have established an evidence-based national developmental scale, the Tipat Halav Israeli Screening (THIS) scale, on the basis of >3.5 million developmental assessments of >640 000 children aged 0 to 6 years from a diverse multicultural population.15 These developmental assessments, conducted by trained public health nurses in a nationwide program, were used to determine normal attainment ages of 59 developmental milestones in 4 domains: gross motor, fine motor, language, and personal–social. THIS developmental scale is currently adapted by the Israeli Ministry of Health as the national developmental surveillance protocol.
The authors of the current report aim to compare THIS and the newly updated CDC checklists. Specifically, we assessed the suggested normative attainment age of the updated CDC checklists using the achievement rate of compatible milestones included in the THIS scale. Because of the large size of our cohort and the diversity of the Israeli population, this analysis, which provides new data-driven evidence about milestone attainment, may contribute to optimizing developmental surveillance in multicultural populations.
Methods
The developmental norms of THIS scale were derived from a cross-sectional population-based study conducted between January 2014 and September 2020, as previously described.15 Briefly, developmental surveillance (ages birth to 6 years) in Israel is performed routinely according to national standards by trained public health nurses in ∼1000 maternal child health clinics (MCHC). The services provided at these clinics also include routine immunization, growth monitoring, and health education. Parents are instructed to visit the MCHC after hospital discharge and then at ages 1, 2, 4, 6, 9, 12, 18, 24, 36, 48, and 60 months.16
Developmental Assessments Used for THIS Scale
The standardized screening protocol of MCHC uses developmental milestones in 4 domains: gross motor, fine motor, language, and personal–social. The milestones included in the scale were chosen by a Ministry of Health task force consisting of pediatricians, nurses, physical therapists, speech pathologists, occupational therapists, and child psychologists. At each visit, a predefined group of age-related milestones is evaluated, according to the expected development at that age. There are 9 such groups of milestones, for ages 1 to 3 months, 3 to 6 months, 6 to 9 months, 9 to 12 months, 12 to 18 months, 18 to 24 months, 24 to 36 months, 36 to 48 months, and 48 to 72 months. The child’s performance in each milestone is reported as observed in the clinic. In cases of objective difficulty in appropriate evaluation, milestone achievements are documented according to the parents’ report. All results are documented within an electronic medical record.
Study Cohorts
The updated CDC milestones for developmental surveillance were based on multiple studies, without uniform standardized inclusion and exclusion criteria. Some of these studies included healthy, typically developing children,17 whereas other studies included all full-term children.18 The assessment of the normative attainment ages recommended by the CDC checklists was therefore performed on 2 cohorts. The first cohort (NORMAL-FT) was the original THIS cohort, which included all children born between January 2014 and September 2020 who visited MCHCs for developmental evaluation (n = 839 574), excluding children at high risk for developmental delay, such as those with preterm birth (gestational age of <37 weeks), low birth weight (<2.5 kg), underweight children (<3% according to standardized child growth charts), abnormal head circumference measurement (microcephaly [<3%] or macrocephaly [>97%] according to standardized child growth charts), missing gestational age at delivery, and visits without developmental data or without the child’s age. The NORMAL-FT cohort included 643 958 children. The second cohort (ALL-FT) consisted of the same initial population but excluded only preterm children and missing data, including 758 300 children.
Comparison of Developmental Norms
To derive the Israeli developmental norms, for each milestone, children were grouped by their age during milestone evaluation and the achievement rate at each age was calculated. The obtained curve of achievement rate by age was then smoothed and interpolated, and the threshold ages at which the achievement rate surpassed 75%, 90%, and 95% were derived.
The norms derived from NORMAL-FT and ALL-FT cohorts were then compared with the updated CDC milestones. Because the exact definition of the evaluated milestones varies between these scales, we restricted the analysis to those milestones that bear enough resemblance to enable comparison, as determined by a thorough review of both protocols by 2 researchers. The reviewers considered not only the resemblance of the milestone titles but also the elaborated guidance for assessing the milestone by each protocol. Milestones that were not fully identical, but their definition by THIS was more difficult to attain than by CDC, were also included. The CDC milestone threshold age was defined as the age at which ≥75% of the children would be expected to achieve the milestone. For each of the comparable milestones, the attainment rate of the Israeli children at the CDC threshold age was extracted from the NORMAL-FT and ALL-FT developmental norms. For most of the milestones, the attainment rates of the Israeli children at the earliest evaluation age were >80%, and, therefore, the ages of attainment by 75% of the children could not be thoroughly compared. However, we used a subset of milestones, for which the attainment ages of 75% to 80% of the children were available, and compared these ages with the CDC recommended ages. The study protocol was approved by the Soroka Medical Center Institutional Review Board.
Results
The flowchart of study participants is shown in Fig 1, and the main characteristics of the 2 cohorts are specified in Table 1. The demographic variables elaborated in Table 1 emphasize the diverse multicultural population of children living in Israel. This population consists of multiple ethnic groups, such as Jews, Arabs, and Druse, with possible differences in culture and spoken language at home. Many Israeli Jews are second- or third-generation descendants of immigrants from Europe, Asia, and North Africa. Accordingly, in our cohorts, almost one-fifth of the children’s mothers immigrated to Israel, mostly from Europe and the former Soviet Union.
Study participant flowchart for the cohort of all full-term born children (ALL-FT) and for the cohort of healthy, typically developing children (NORMAL-FT).
Study participant flowchart for the cohort of all full-term born children (ALL-FT) and for the cohort of healthy, typically developing children (NORMAL-FT).
Study Population Characteristics
Cohort Characteristics . | NORMAL-FT . | ALL-FT . | |
---|---|---|---|
n | 643 958 | 758 300 | |
Average number of visits per child (SD) | 5.86 (2.4) | 5.89 (2.4) | |
Ethnic group, n (%) | Arab | 140 525 (21.8) | 163 378 (21.5) |
Druse | 11 796 (1.8) | 13 483 (1.8) | |
Jewish | 392 634 (61.0) | 464 682 (61.3) | |
Missing | 76 333 (11.9) | 90 555 (11.9) | |
Other | 22 670 (3.5) | 26 202 (3.5) | |
Mother’s birth country, n (%) | Israel | 528 861 (82.1) | 622 030 (82.0) |
Other | 58 983 (9.2) | 70 109 (9.2) | |
Europe | 25 180 (3.9) | 29 323 (3.9) | |
Former Soviet Union | 22 240 (3.5) | 25 807 (3.4) | |
Ethiopia | 8644 (1.3) | 10 969 (1.4) | |
Missing | 50 (0.0) | 62 (0.0) | |
Employment status, n (%) | Missing | 199 544 (31.0) | 235 675 (31.1) |
Not working | 131 703 (20.5) | 156 256 (20.6) | |
Student | 28 514 (4.4) | 33 145 (4.4) | |
Working | 284 197 (44.1) | 333 224 (43.9) | |
Mother’s education level, n (%) | Academic | 195 799 (30.4) | 228 520 (30.1) |
Elementary | 13 442 (2.1) | 16 230 (2.1) | |
High School | 171 411 (26.6) | 201 011 (26.5) | |
Missing | 199 021 (30.9) | 236 799 (31.2) | |
Tertiary Education | 64 285 (10.0) | 75 740 (10.0) | |
Mother’s family status, n (%) | Divorced | 6343 (1.0) | 7598 (1.0) |
Married | 566 747 (88.0) | 666 352 (87.9) | |
Missing | 43 380 (6.7) | 51 467 (6.8) | |
Other | 27 165 (4.2) | 32 496 (4.3) | |
Widower | 323 (0.1) | 387 (0.1) | |
Consanguinity, n (%) | No | 606 227 (94.1) | 713 362 (94.1) |
Yes | 37 731 (5.9) | 44 938 (5.9) | |
Pregnancy wk, median [Q1, Q3] | 39.5 [38.6, 40.3] | 39.5 [38.5, 40.3] | |
Birth wt, mean (SD) | 3.3 (0.4) | 3.3 (0.4) | |
Apgar score 1 minute, n (%) | <8 | 18 862 (2.9) | 23 621 (3.1) |
≥8 | 613 747 (95.3) | 719 106 (94.8) | |
Missing | 11 349 (1.8) | 15 573 (2.1) | |
Apgar score 5 minutes, n (%) | <8 | 4112 (0.6) | 5257 (0.7) |
≥8 | 624 688 (97.0) | 733 009 (96.7) | |
Missing | 15 158 (2.4) | 20 034 (2.6) | |
Head circumference, mean (SD) | 34.5 (1.3) | 34.4 (1.4) | |
Type of birth, n (%) | Cesarean section | 92 540 (14.4) | 115 273 (15.2) |
Instrumental | 34 008 (5.3) | 39 920 (5.3) | |
Missing | 31 946 (5.0) | 38 623 (5.1) | |
Spontaneous | 485 464 (75.4) | 564 484 (74.4) | |
Newborn position, n (%) | Breech | 14 532 (2.3) | 19 267 (2.5) |
Head | 540 304 (83.9) | 631 402 (83.3) | |
Missing | 82 832 (12.9) | 99 778 (13.2) | |
Other | 6290 (1.0) | 7853 (1.0) | |
Mother’s age, n (%) | ≤20 | 7101 (1.1) | 8456 (1.1) |
≤40 | 584 833 (90.8) | 687 590 (90.7) | |
>40 | 45 095 (7.0) | 54 140 (7.1) | |
Missing | 6929 (1.1) | 8114 (1.1) |
Cohort Characteristics . | NORMAL-FT . | ALL-FT . | |
---|---|---|---|
n | 643 958 | 758 300 | |
Average number of visits per child (SD) | 5.86 (2.4) | 5.89 (2.4) | |
Ethnic group, n (%) | Arab | 140 525 (21.8) | 163 378 (21.5) |
Druse | 11 796 (1.8) | 13 483 (1.8) | |
Jewish | 392 634 (61.0) | 464 682 (61.3) | |
Missing | 76 333 (11.9) | 90 555 (11.9) | |
Other | 22 670 (3.5) | 26 202 (3.5) | |
Mother’s birth country, n (%) | Israel | 528 861 (82.1) | 622 030 (82.0) |
Other | 58 983 (9.2) | 70 109 (9.2) | |
Europe | 25 180 (3.9) | 29 323 (3.9) | |
Former Soviet Union | 22 240 (3.5) | 25 807 (3.4) | |
Ethiopia | 8644 (1.3) | 10 969 (1.4) | |
Missing | 50 (0.0) | 62 (0.0) | |
Employment status, n (%) | Missing | 199 544 (31.0) | 235 675 (31.1) |
Not working | 131 703 (20.5) | 156 256 (20.6) | |
Student | 28 514 (4.4) | 33 145 (4.4) | |
Working | 284 197 (44.1) | 333 224 (43.9) | |
Mother’s education level, n (%) | Academic | 195 799 (30.4) | 228 520 (30.1) |
Elementary | 13 442 (2.1) | 16 230 (2.1) | |
High School | 171 411 (26.6) | 201 011 (26.5) | |
Missing | 199 021 (30.9) | 236 799 (31.2) | |
Tertiary Education | 64 285 (10.0) | 75 740 (10.0) | |
Mother’s family status, n (%) | Divorced | 6343 (1.0) | 7598 (1.0) |
Married | 566 747 (88.0) | 666 352 (87.9) | |
Missing | 43 380 (6.7) | 51 467 (6.8) | |
Other | 27 165 (4.2) | 32 496 (4.3) | |
Widower | 323 (0.1) | 387 (0.1) | |
Consanguinity, n (%) | No | 606 227 (94.1) | 713 362 (94.1) |
Yes | 37 731 (5.9) | 44 938 (5.9) | |
Pregnancy wk, median [Q1, Q3] | 39.5 [38.6, 40.3] | 39.5 [38.5, 40.3] | |
Birth wt, mean (SD) | 3.3 (0.4) | 3.3 (0.4) | |
Apgar score 1 minute, n (%) | <8 | 18 862 (2.9) | 23 621 (3.1) |
≥8 | 613 747 (95.3) | 719 106 (94.8) | |
Missing | 11 349 (1.8) | 15 573 (2.1) | |
Apgar score 5 minutes, n (%) | <8 | 4112 (0.6) | 5257 (0.7) |
≥8 | 624 688 (97.0) | 733 009 (96.7) | |
Missing | 15 158 (2.4) | 20 034 (2.6) | |
Head circumference, mean (SD) | 34.5 (1.3) | 34.4 (1.4) | |
Type of birth, n (%) | Cesarean section | 92 540 (14.4) | 115 273 (15.2) |
Instrumental | 34 008 (5.3) | 39 920 (5.3) | |
Missing | 31 946 (5.0) | 38 623 (5.1) | |
Spontaneous | 485 464 (75.4) | 564 484 (74.4) | |
Newborn position, n (%) | Breech | 14 532 (2.3) | 19 267 (2.5) |
Head | 540 304 (83.9) | 631 402 (83.3) | |
Missing | 82 832 (12.9) | 99 778 (13.2) | |
Other | 6290 (1.0) | 7853 (1.0) | |
Mother’s age, n (%) | ≤20 | 7101 (1.1) | 8456 (1.1) |
≤40 | 584 833 (90.8) | 687 590 (90.7) | |
>40 | 45 095 (7.0) | 54 140 (7.1) | |
Missing | 6929 (1.1) | 8114 (1.1) |
SD, standard deviation.
There were 35 milestones across all developmental domains whose definitions by both tools were compatible (Table 2). Six milestones were not comparable because their evaluation in the Israeli cohort started later than their CDC-defined age (range of age difference 6–12 months). Of the remaining 29 milestones, there were 10 gross motor, 6 fine motor, 8 language, and 5 personal–social milestones that represent all 9 age-related groups of milestones. At the age recommended by the CDC checklist, the attainment rates of the children in the NORMAL-FT cohort were >95% in 16 milestones (55%), 90% to 95% in 7 milestones (24%), 85% to 90% in 3 milestones (10%), and 80% to 85% in 2 milestones (7%). There was only 1 milestone in which the attainment rate of the Israeli children at the CDC-defined age was 65% to 70%, lower than the expected rate of 75% (“gets to a sitting position by herself”). Overall, the median attainment rate was 96.3% (interquartile range: 91.1%–98.6%). The results obtained from the ALL-FT cohort were similar, with a minor decrease in the attainment rates and a median attainment rate of 95.2% (interquartile range: 90.4%–98.3%). Thus, for almost all comparable milestones, of all domains and in all age groups, healthy children in Israel performed significantly earlier than expected by the CDC-defined threshold age (Fig 2).
Milestone attainment rate of the Israeli children at the CDC recommended age, across 4 developmental domains. ALL-FT is the cohort of all full-term born children. NORMAL-FT is the cohort of healthy, typically developing children.
Milestone attainment rate of the Israeli children at the CDC recommended age, across 4 developmental domains. ALL-FT is the cohort of all full-term born children. NORMAL-FT is the cohort of healthy, typically developing children.
Comparison of THIS and CDC Milestone Attainment Rate at the CDC-Recommended Age
THIS Milestone . | CDC Milestone . | CDC Age Threshold (≥75%) (mo) . | % Attainment in Israel at CDC Age Threshold (NORMAL-FT Cohort) . | % Attainment in Israel at CDC Age Threshold (ALL-FT Cohort) . |
---|---|---|---|---|
Vocalizes in response to human voice | Makes sounds back when you talk to him | 4 | >95% | >95% |
Smiles responsively | Smiles when you talk to or smile at her | 2 | >95% | >95% |
Raises head | Holds head up when on tummy | 2 | 85%–90% | 85%–90% |
Makes various sounds including constants (ie, mm, rr, gg) | Makes sounds like “ooo” and “aahhh” (cooing) | 4 | >95% | >95% |
Hands together, manipulates fingers | Looks at his hands with interest | 4 | >95% | >95% |
Head and chest up in prone position | Pushes up onto elbows/forearms when on tummy | 4 | 90%–95% | 90%–95% |
Transfers an object from one hand to the other | Moves things from 1 hand to her other hand | 9 | >95% | >95% |
Makes repetitive syllables, constant, or vowels | Makes different sounds like “mama” or “baba” | 9 | >95% | >95% |
Rolls over from abdomen to back and back to abdomen | Rolls from tummy to back | 6 | 80%–85% | 75%–80% |
Taps two objects playfully | Bangs 2 things together | 9 | >95% | >95% |
Responds when addressed by name | Looks when you call his name | 9 | >95% | >95% |
Responds differently to familiar and stranger | Knows familiar people | 6 | N/A (evaluated from 9m) | N/A |
Feeds self | Feeds herself with her fingers | 18 | >95% | >95% |
Uses thumb, fingers grasp | Picks things up between thumb and pointer finger, like small bits of food | 12 | >95% | >95% |
Understands simple instructions | Follows directions given with both a gesture and words. For example, he gives you a toy when you hold out your hand and say, “Give me the toy.” | 15 | >95% | >95% |
Gets to sit without support | Gets to a sitting position by herself | 9 | 65%–70% | 65%–70% |
Walks with assistance | Walks, holding onto furniture | 12 | 90%–95% | 90%–95% |
Points at familiar objects to request | Looks at a familiar object when you name it | 15 | 90%–95% | 90%–95% |
Pulls to stand | Pulls up to stand | 12 | 90%–95% | 85%–90% |
Says 2 to 3 words | Tries to say 1 or 2 words besides mama or dada, like “ba” for ball or “da” for dog | 15 | 90%–95% | 90%–95% |
Walks without assistance | Walks without holding onto anyone or anything | 18 | >95% | >95% |
Eats independently with a spoon | Eats with a spoon | 24 | >95% | >95% |
Builds a tower of cubes | Stacks at least 2 small objects, like blocks | 15 | N/A (evaluated from 18m) | N/A |
Squeezes and sticks out lips to give a kiss | Uses more gestures than just waving and pointing, like blowing a kiss or nodding yes | 24 | 90%–95% | 90%–95% |
Composes a sentence of at least two words | Says at least 2 words together, like “more milk” | 24 | 80%–85% | 80%–85% |
Runs well without falling | Runs | 24 | >95% | >95% |
Climbs up and down the stairs without an adult’s assistance | Walks (not climbs) up a few stairs with or without help | 24 | >95% | >95% |
Understands actions and speech without gestures | Follows 1-step directions without any gestures, like giving you the toy when you say, “Give it to me.” | 18 | N/A (evaluated from 24m) | N/A |
Puts on shoes and dresses independently without buttoning | Puts on some clothes by himself, like loose pants or a jacket | 36 | 90%–95% | 90%–95% |
Imitates patterns (+) and copies circles | Draws a circle when you show him how | 36 | 85%–90% | 85%–90% |
Plays with peer group | Notices other children and joins them to play | 36 | N/A (evaluated from 48m) | N/A |
Understandable speech | Talks well enough for others to understand, most of the time | 36 | 85%–90% | 85%–90% |
Uses correct verbs and tense to describe a picture | Says what action is happening in a picture when asked, like running, eating, or playing | 36 | N/A (evaluated from 48m) | N/A |
Answers orientation questions such as name or age | Says first name when asked | 36 | N/A (evaluated from 48m) | N/A |
Jumps on 1 leg | Hops on 1 foot | 60 | >95% | >95% |
THIS Milestone . | CDC Milestone . | CDC Age Threshold (≥75%) (mo) . | % Attainment in Israel at CDC Age Threshold (NORMAL-FT Cohort) . | % Attainment in Israel at CDC Age Threshold (ALL-FT Cohort) . |
---|---|---|---|---|
Vocalizes in response to human voice | Makes sounds back when you talk to him | 4 | >95% | >95% |
Smiles responsively | Smiles when you talk to or smile at her | 2 | >95% | >95% |
Raises head | Holds head up when on tummy | 2 | 85%–90% | 85%–90% |
Makes various sounds including constants (ie, mm, rr, gg) | Makes sounds like “ooo” and “aahhh” (cooing) | 4 | >95% | >95% |
Hands together, manipulates fingers | Looks at his hands with interest | 4 | >95% | >95% |
Head and chest up in prone position | Pushes up onto elbows/forearms when on tummy | 4 | 90%–95% | 90%–95% |
Transfers an object from one hand to the other | Moves things from 1 hand to her other hand | 9 | >95% | >95% |
Makes repetitive syllables, constant, or vowels | Makes different sounds like “mama” or “baba” | 9 | >95% | >95% |
Rolls over from abdomen to back and back to abdomen | Rolls from tummy to back | 6 | 80%–85% | 75%–80% |
Taps two objects playfully | Bangs 2 things together | 9 | >95% | >95% |
Responds when addressed by name | Looks when you call his name | 9 | >95% | >95% |
Responds differently to familiar and stranger | Knows familiar people | 6 | N/A (evaluated from 9m) | N/A |
Feeds self | Feeds herself with her fingers | 18 | >95% | >95% |
Uses thumb, fingers grasp | Picks things up between thumb and pointer finger, like small bits of food | 12 | >95% | >95% |
Understands simple instructions | Follows directions given with both a gesture and words. For example, he gives you a toy when you hold out your hand and say, “Give me the toy.” | 15 | >95% | >95% |
Gets to sit without support | Gets to a sitting position by herself | 9 | 65%–70% | 65%–70% |
Walks with assistance | Walks, holding onto furniture | 12 | 90%–95% | 90%–95% |
Points at familiar objects to request | Looks at a familiar object when you name it | 15 | 90%–95% | 90%–95% |
Pulls to stand | Pulls up to stand | 12 | 90%–95% | 85%–90% |
Says 2 to 3 words | Tries to say 1 or 2 words besides mama or dada, like “ba” for ball or “da” for dog | 15 | 90%–95% | 90%–95% |
Walks without assistance | Walks without holding onto anyone or anything | 18 | >95% | >95% |
Eats independently with a spoon | Eats with a spoon | 24 | >95% | >95% |
Builds a tower of cubes | Stacks at least 2 small objects, like blocks | 15 | N/A (evaluated from 18m) | N/A |
Squeezes and sticks out lips to give a kiss | Uses more gestures than just waving and pointing, like blowing a kiss or nodding yes | 24 | 90%–95% | 90%–95% |
Composes a sentence of at least two words | Says at least 2 words together, like “more milk” | 24 | 80%–85% | 80%–85% |
Runs well without falling | Runs | 24 | >95% | >95% |
Climbs up and down the stairs without an adult’s assistance | Walks (not climbs) up a few stairs with or without help | 24 | >95% | >95% |
Understands actions and speech without gestures | Follows 1-step directions without any gestures, like giving you the toy when you say, “Give it to me.” | 18 | N/A (evaluated from 24m) | N/A |
Puts on shoes and dresses independently without buttoning | Puts on some clothes by himself, like loose pants or a jacket | 36 | 90%–95% | 90%–95% |
Imitates patterns (+) and copies circles | Draws a circle when you show him how | 36 | 85%–90% | 85%–90% |
Plays with peer group | Notices other children and joins them to play | 36 | N/A (evaluated from 48m) | N/A |
Understandable speech | Talks well enough for others to understand, most of the time | 36 | 85%–90% | 85%–90% |
Uses correct verbs and tense to describe a picture | Says what action is happening in a picture when asked, like running, eating, or playing | 36 | N/A (evaluated from 48m) | N/A |
Answers orientation questions such as name or age | Says first name when asked | 36 | N/A (evaluated from 48m) | N/A |
Jumps on 1 leg | Hops on 1 foot | 60 | >95% | >95% |
N\A, milestones that were not comparable since their evaluation in the Israeli cohort started later than their CDC-defined age. The THIS Milestone is available at www.eng.linkcaring.com/this-scale.
There were 8 milestones for which the attainment ages of 75% to 80% of the Israeli children were available and could be compared with the CDC recommended ages (Table 3). Among these milestones, 6 milestones were attained in our 2 cohorts at a younger age (age difference 1–3.5 months), 1 milestone as attained at an older age (age difference 1.1 months), and, for 1 milestone, the attainment ages were the same in both scales.
Comparison of THIS and CDC Milestone Attainment Age for 75% to 80% of the Children
THIS Milestone . | CDC Milestone . | CDC Age Threshold (≥75%) (mo) . | THIS Age Threshold (75%–80%) NORMAL-FT Cohort . | THIS Age Threshold (75%–80%) ALL-FT Cohort . |
---|---|---|---|---|
Vocalizes in response to human voice | Makes sounds back when you talk to him | 4 | 0.45 | 0.47 |
Smiles responsively | Smiles when you talk to or smile at her | 2 | 0.66 | 0.74 |
Head and chest up in prone position | Pushes up onto elbows/forearms when on tummy | 4 | 3 | 3 |
Rolls over from abdomen to back and back to abdomen | Rolls from tummy to back | 6 | 6 | 6 |
Taps 2 objects playfully | Bangs 2 things together | 9 | 6 | 6 |
Gets to sit without support | Gets to a sitting position by herself | 9 | 10.1 | 10.2 |
Pulls to stand | Pulls up to stand | 12 | 10.3 | 10.4 |
Composes a sentence of at least 2 words | Says at least 2 words together, like “more milk” | 24 | 22.2 | 22.3 |
THIS Milestone . | CDC Milestone . | CDC Age Threshold (≥75%) (mo) . | THIS Age Threshold (75%–80%) NORMAL-FT Cohort . | THIS Age Threshold (75%–80%) ALL-FT Cohort . |
---|---|---|---|---|
Vocalizes in response to human voice | Makes sounds back when you talk to him | 4 | 0.45 | 0.47 |
Smiles responsively | Smiles when you talk to or smile at her | 2 | 0.66 | 0.74 |
Head and chest up in prone position | Pushes up onto elbows/forearms when on tummy | 4 | 3 | 3 |
Rolls over from abdomen to back and back to abdomen | Rolls from tummy to back | 6 | 6 | 6 |
Taps 2 objects playfully | Bangs 2 things together | 9 | 6 | 6 |
Gets to sit without support | Gets to a sitting position by herself | 9 | 10.1 | 10.2 |
Pulls to stand | Pulls up to stand | 12 | 10.3 | 10.4 |
Composes a sentence of at least 2 words | Says at least 2 words together, like “more milk” | 24 | 22.2 | 22.3 |
https://israel.linkcaring.com/Guide.html (in Hebrew).
Discussion
Developmental milestone norms are an essential component of the routine developmental surveillance conducted worldwide. Accordingly, the use of milestone checklists by pediatricians has increased from 53% in 2002 to 90% in 2016.19 However, there are considerable inconsistencies regarding the normative milestone attainment age between different sources.12,13 In the newly updated CDC checklists, the suggested age threshold is the age at which most children (≥75%) are expected to achieve the milestone, based on existing CDC milestones, literature review, and developmental resources.
In the current report, for each of the comparable milestones, the actual attainment rate at the CDC-suggested age was obtained from developmental assessments of 758 300 full-term Israeli children aged 0 to 6 years, with a subgroup of 643 958 healthy, typically developing children. In both cohorts, for all milestones but 1, the attainment rate was considerably higher than 75%, indicating that these milestones were achieved by most of the Israeli children at an earlier age than suggested by the CDC checklists. The replication of the results on the larger ALL-FT cohort (excluding only preterms) implies that the exclusion criteria used in the NORMAL-FT cohort do not have a major effect on the milestones attainment age when evaluating a large population.
Only 29 of 150 CDC milestones were comparable in this study; however, the milestones available for comparison represent 4 developmental domains and were evaluated at all relevant age ranges. Because the same tendency was observed in almost all comparable milestones, we believe these differences require consideration. The observed discrepancies might be partially explained by the unique dataset of Israeli children, representing a nationwide population, compared with small to medium samples in other studies that were used to establish the CDC checklists. In addition, the Israeli norms were based on developmental surveillance conducted by trained nurses rather than by parent-filled questionnaires.
Moreover, our cohort was based on evaluations conducted within recent years, whereas the CDC checklist used all available relevant studies spanning >40 years of research. This difference may be related to the observed trend of earlier attainment age, similarly to earlier studies that revealed a rise in IQ scores (“Flynn effect”) and in developmental scores over time.20,21 Nevertheless, although the THIS developmental scale is based on a large heterogeneous, multicultural population, it still may not be fully applicable to populations from other geographies and cultures. Another limitation stems from the selection of comparable milestones; although our selection was based on a meticulous review by the research team, some of the pairs of compared milestones may not be completely equivalent. This is a general challenge that applies to any comparison between milestones from different evaluation tools. In a broader view, simplifying the language describing the milestone assessment is important for conducting uniform evaluations and for increasing reliability. To make sure all health care providers will perform evaluations based on the new scale similarly, we have created explanatory animation guidance,1 which can be available in multiple languages on request. Because of the key importance of the milestone norms for surveillance, as well as for developmental screening and diagnostic tools, further research is required to assess the validity of milestone norms, and their transferability to different populations worldwide. It might be essential to monitor possible changes in milestone norms among subpopulations to enable adjustments of developmental scales and facilitate a more personalized developmental surveillance. We believe that MCHC’s large national cohort, with data continuously collected and updated, may offer a unique opportunity to address important open questions in the field of child development, such as longitudinal trends in developmental norms (including changes during the coronavirus disease 2019 pandemic), norm adjustments for preterm children, differences between sexes, and effects of social determinants on early development. We intend to address some of these questions in future studies.
Conclusions
For almost all comparable developmental milestones of all domains and all age groups, the children of the Israel cohorts achieved the milestones earlier than expected by the CDC-defined threshold age. Evidence-based analysis of milestone norms among different populations may enable adjustments of developmental scales and facilitate a more personalized developmental surveillance.
Drs Sadaka, Sudry, and Amit conceptualized and designed the study, conducted the data analysis, drafted the initial manuscript, and reviewed and revised the manuscript; Drs Avgil Tsadok and Akiva conceptualized and designed the study and critically reviewed the manuscript for important intellectual content; Drs Zimmerman and Yardeni, Mrs Baruch, and Mr Ben Moshe designed the data collection instruments, collected data, facilitated access to the data, and critically reviewed the manuscript; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
FUNDING: No external funding.
CONFLICT OF INTEREST DISCLOSURES: The authors have indicated they have no potential conflicts of interest relevant to this article to disclose.
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