“Learn the Signs. Act Early.”: Updates and Implications for Physical Therapists

Abstract

Purpose:

In early 2022, the Centers for Disease Control and Prevention (CDC) updated their developmental surveillance milestone checklists. The purpose of this article is to clarify and interpret the updates from a physical therapist perspective and to discuss implications of the new milestones for physical therapists.

Summary of Key Points:

• The CDC’s updated checklists provide clear, consistent, easy to use, and evidence-based developmental milestones to prompt discussion with families.

• The new checklists do not represent a lowering of standards and will likely increase, not decrease, referrals for screening, evaluation, and services.

• Crawling has been removed from the milestone checklists, as the current evidence suggests that crawling is highly variable and not essential for development.

Conclusions and Recommendations for Clinical Practice:

The updated milestone checklists will facilitate bringing vital services to children who need them. Physical therapists should support our primary care colleagues in implementing this useful program.

In early 2022, the Centers for Disease Control and Prevention (CDC) updated the materials for their developmental surveillance program, “Learn the Signs. Act Early.” The updates to public motor milestone checklists sparked intense discussion in the pediatric physical therapy community. As experts in early child development, early diagnosis, and early intervention, we aim to clarify the content of the updated developmental milestone checklists, provide an evidence-based interpretation of the new milestones, and discuss implications of the new milestones for physical therapists.

CDC’s Developmental Surveillance Program: “Learn the Signs. Act Early.”

In 1986, the United States (US) government recognized the need for early detection and intervention for children with developmental disabilities with the development of the Early Intervention Program for Infants and Toddlers with Disabilities under the Individuals with Disabilities Education Act (IDEA; 20; U.S.C., Section 1431). The implementation of this program underscores the nation’s commitment to acting early to improve the lives of individuals with developmental disabilities. Essential to the implementation of early intervention programs is the identification of children with delays or disabilities as early as possible.^1,2

Developmental surveillance is a process aimed at identifying children in the general population who may be at risk for developmental delays.^3,4 Surveillance is the first step in a three-pronged systematic method that also includes screening—the use of standardized, validated measures to determine risk—and evaluation (or assessment)—the process of quantifying specific delays and informing a clinical diagnosis.⁴ Screening and evaluation are commonly performed by early intervention providers including physical therapists. Common screening tools include the Ages and Stages Questionnaire⁵ and the Survey of Well-Being in Young Children⁶; evaluation tools include the Bayley Scales of Infant and Toddler Development (Bayley),⁷ the Peabody Developmental Motor Scales (PDMS),⁸ and the Developmental Assessment of Young Children (DAYC).⁹ Surveillance, in contrast, is a task for caregivers and primary care practitioners. The focus of surveillance is to assist in initiating conversations between families and their providers about children’s development. Ideally, surveillance identifies children who are appropriate for screening, screening identifies children who require evaluation, and evaluation determines which children are appropriate for intervention.

The “Learn the Signs. Act Early.” program was launched by the CDC in 2004 as a comprehensive developmental surveillance tool. The goals of the program were centered on caregivers: to promote caregivers’ understanding of developmental milestones, spur conversations between caregivers and healthcare providers, and improve caregivers’ ability to act on concerns about their child’s development.^10,11 At the heart of the “Learn the Signs. Act Early.” program are the milestone checklists. Forms for a series of ages between 2 months and 5 years (designed to coincide with the timing of recommended well child visits) list key skills in four developmental domains—Social/Emotional, Language/Communication, Cognitive, and Movement/Physical Development. The checklists provide information to assist caregivers in monitoring their children’s achievement of developmental skills and prompt conversations with pediatricians when children are not achieving milestones on a typical schedule. Note that whereas screening and assessment tools are validated, surveillance tools are not.^3,4 The CDC’s milestone checklists were initially developed based on expert opinion, without clear sources of evidence or objective criteria for the inclusion of skills or the association of skills with particular ages.^3,12

Dissemination of the CDC milestone information has been successful in increasing both parental awareness of developmental milestones¹¹ and conversations about development at well-child medical visits.¹⁰ Surveillance ultimately leads to intervention: Children who participated in both developmental surveillance and screening were more likely to receive early intervention services compared to those receiving screening alone.¹³ Unfortunately, in 2016–2017, only 37% of parents across the US reported receiving developmental surveillance (i.e., a provider eliciting their concerns about their child’s development).¹⁴

2022 Updates to the CDC’s “Learn the Signs. Act Early.”

In 2019, the CDC called for improvements in the “Learn the Signs. Act Early.” materials via the development of concrete criteria for item inclusion, as well as the addition of checklists for 15 and 30 months to correspond with additional well child visits.³ A group of subject matter experts (developmental-behavioral, neurodevelopmental, and general pediatricians; psychologists; and a special education/early intervention expert) convened by the American Academy of Pediatrics was tasked with developing the criteria and revising the milestone checklists. Their procedure is detailed in an open access manuscript in the journal Pediatrics.³

The 11 criteria identified to assess milestones included “Milestones are included at the age most (≥75%) children would be expected to demonstrate the milestone,” “Are easy for families of different social, cultural, and ethnic backgrounds to observe and use,” and “Use plain language, avoiding vague terms like may, can, and begins.”³ The group of subject matter experts performed a literature search to identify normative data for the achievement of milestones at the 75^th percentile, and used these and other resources to inform the placement of items on the milestone checklists.

In addition to revisions to the individual milestone items, the second major change was the streamlining of two separate checklists for each age into one. The old versions each contained a list of age-appropriate milestones (“What Most Babies Do by This Age”) as well as a second list containing what may be referred to as “red flag” items. The text encouraged caregivers to “Act Early” if their child meets any items on the second list. For example, the 18-month checklist encouraged talking to the child’s doctor if the child “can’t walk.” The new forms are simplified to contain only the primary list of milestones, and now instruct caregivers to talk to the doctor if the child is “not meeting one or more milestones.” This has removed redundancy, clarified the function of the milestone lists, and simplified the recommendations for caregivers.

Milestones in all four areas have been updated in the recent revision. In this commentary, we focus on changes made to the Movement/Physical Development milestones to reflect our areas of expertise as physical therapists. Table 1 provides a side-by-side comparison of the original and updated motor milestone lists for each age.

Table 1.

Original vs. updated Movement/Physical Development milestones

	2004 Milestones	2022 Milestones
2 months	SAME OR SIMILAR
	• Can hold head up and begins to push up when lying on tummy • Makes smoother movements with arms and legs	• Holds head up when on tummy • Moves both arms and both legs
	MOVED OR DIFFERENT
		• Opens hands briefly
4 months	SAME OR SIMILAR
	• Holds head steady, unsupported • Can hold a toy and shake it and swing at dangling toys • Brings hands to mouth • When lying on stomach, pushes up to elbows	• Holds head steady without support when you are holding her • Holds a toy when you put it in his hand • Uses her arm to swing at toys • Brings hands to mouth • Pushes up onto elbows/forearms when on tummy
	MOVED OR DIFFERENT
	• May be able to roll over from tummy to back • Pushes down on legs when feet are on a hard surface
6 months	SAME OR SIMILAR
	• Rolls over in both directions (front to back, back to front) • Begins to sit without support	• Rolls from tummy to back • Leans on hands to support himself when sitting
	MOVED OR DIFFERENT
	• When standing, supports weight on legs and might bounce • Rocks back and forth, sometimes crawling backward before moving forward	• Pushes up with straight arms when on tummy
9 months	SAME OR SIMILAR
	• Can get into sitting position • Sits without support	• Gets to a sitting position by herself • Sits without support
	MOVED OR DIFFERENT
	• Pulls to stand • Stands, holding on • Crawls	• Moves things from one hand to her other hand • Uses fingers to “rake” food towards himself
1 year	SAME OR SIMILAR
	• Pulls up to stand, walks holding on to furniture (“cruising”)	• Pulls up to stand • Walks, holding on to furniture
	MOVED OR DIFFERENT
	• May take a few steps without holding on • Gets to a sitting position without help • May stand alone	• Drinks from a cup without a lid, as you hold it • Picks things up between thumb and pointer finger, like small bits of food
15 months	SAME OR SIMILAR
	NA: No 15-month checklist in original version	NA: No 15-month checklist in original version
	MOVED OR DIFFERENT
		• Takes a few steps on his own • Uses fingers to feed herself some food
18 months	SAME OR SIMILAR
	• Walks alone • Drinks from a cup	• Walks without holding on to anyone or anything • Drinks from a cup without a lid and may spill sometimes
	MOVED OR DIFFERENT
	• Eats with a spoon • May walk up steps and run • Can help undress herself • Pulls toys while walking	• Tries to use a spoon • Climbs on and off a couch or chair without help • Scribbles • Feeds herself with her fingers
2 years	SAME OR SIMILAR
	• Kicks a ball • Begins to run • Walks up and down stairs holding on	• Kicks a ball • Runs • Walks (not climbs) up a few stairs with or without help
	MOVED OR DIFFERENT
	• Climbs onto and down from furniture without help • Stands on tiptoe • Throws ball overhand • Makes or copies straight lines and circles	• Eats with a spoon
30 months	SAME OR SIMILAR
	NA: No 30-month checklist in original version	NA: No 30-month checklist in original version
	MOVED OR DIFFERENT
		• Takes some clothes off by himself, like loose pants or an open jacket • Uses hands to twist things, like turning doorknobs or unscrewing lids • Jumps off the ground with both feet • Turns book pages, one at a time, when you read to her
3 years	SAME OR SIMILAR
	None	None
	MOVED OR DIFFERENT
	• Runs easily • Climbs well • Pedals a tricycle (3-wheel bike) • Walks up and down stairs, one foot on each step	• Uses a fork • Strings items together, like large beads or macaroni • Puts on some clothes by himself, like loose pants or a jacket
4 years	SAME OR SIMILAR
	• Catches a bounced ball most of the time • Pours, cuts with supervision, and mashes own food	• Catches a large ball most of the time • Serves himself food or pours water, with adult supervision
	MOVED OR DIFFERENT
	• Hops and stands on one foot up to 2 seconds	• Unbuttons some buttons • Holds crayon or pencil between fingers and thumb (not a fist)
5 years	SAME OR SIMILAR
	• Hops; may be able to skip	• Hops on one foot
	MOVED OR DIFFERENT
	• Uses a fork and spoon and sometimes a table knife • Stands on one foot for 10 seconds or longer • Can do a somersault • Can use the toilet on her own • Swings and climbs	• Buttons some buttons

Note. Items listed under Same or Similar are unchanged, partially changed, or reworded between versions. Items listed under Moved or Different were moved to a different age checklist (with or without changes), removed, or added. Italicized items are those that were removed or added.

Evidence Base Informing Motor Milestones

The development of a comprehensive developmental surveillance tool based on empirical evidence is a major advancement. Previously available checklists, including the original version of the CDC tool, were uncited and leaned heavily on clinical opinion. The availability of citations associated with each developmental milestone increases transparency and minimizes bias in the construction of the checklists.

Table 5 in Zubler et al.³ provides detailed information regarding the evidence informing motor milestones. Three types of evidence were used: published normative data (24 articles), information from developmental screening and evaluation tools (3 tools), and published clinical opinion (9 articles, with one also cited as a normative data publication). The strength of this approach is that the evidence is publicly available, allowing parents, medical and educational professionals, and researchers to assess the strength of the evidence for each milestone. In addition, the evidence was drawn from diverse populations of children from multiple countries throughout the Americas, Asia, Africa, and Europe; 7 studies (29%) used a US sample. This increases generalizability across cultures, including immigrant families in the US. A limitation may be that information from only 3 developmental screening and evaluation tools were used for the motor milestones—Ages and Stages Questionnaire (ASQ-3), PEDS: Developmental Milestones (PEDS-DM), Mullen Scales of Early Learning (MSEL) for two fine motor milestones—as they were the only tools that provided item-level age-related data. The screening and assessment tools that are more frequently used in early intervention, e.g. the Bayley, PDMS, and DAYC, do not provide published normative data for individual items and therefore did not inform the motor milestones.

Common Concerns Raised by Physical Therapists

Several concerns have been raised by the pediatric physical therapy community regarding the updated milestone checklists. Heated discussions have abounded in clinical settings, public forums, and on social media. Here we discuss some commonly observed concerns voiced by physical therapists about the updated milestones, with a brief response for each. In the subsequent section, we provide additional clarification in response to these concerns.

Standards have been lowered.

There has been widespread discussion about the new checklists placing milestones at later ages than the prior version. Many therapists fear that changing caregiving habits have led to a population of US children that is developing more slowly. Popular explanations for this trend include the effects of the Safe to Sleep (formerly known as Back to Sleep) campaign on early infant motor skills,^15–18 a perceived increase in the use of infant equipment or “container baby syndrome,”^19–21 and generally greater levels of inactivity in children.^22–24 Therapists argue that the response to changing rates of motor skill acquisition should be to work to improve developmental outcomes rather than shifting the standards.

We argue that the revisions do not, in fact, represent a lowering of standards. Most retained motor milestones have remained on the same age checklists as they were previously; those that now appear at later ages were moved due to the consistent application of a 75^th percentile criterion.

Crawling has been removed as a milestone.

Perhaps the most discussed change in the Movement/Physical Development checklists is the removal of crawling as a milestone. Many pediatric physical therapists contend that crawling is crucial for development, and that infants who do not crawl are at risk for developmental issues later in childhood. The importance of crawling has been a controversial issue in the pediatric therapy community for many years. A wealth of popular media articles and blog posts tout the short- and long-term motor, sensory, and cognitive benefits of crawling, including development of shoulder stability, manipulation skill, body awareness, problem-solving, bilateral coordination, and depth perception.²⁵ In fact, some therapists actively discourage other forms of locomotion for infants who do not crawl. Many clinicians fear that the removal of crawling from the CDC checklists will lend further ammunition to physicians and parents who do not value crawling and will reduce compliance with treatment programs focused on crawling skills.

Given current research and theory in infant motor development (reviewed briefly in the next section), we argue that the evidence for the inclusion of crawling is not strong, and that its removal is appropriate given current research and theory in infant motor development.

New milestones will decrease referrals.

Although the purpose of the updated milestones was to more effectively identify infants who need further screening and evaluation for early intervention services, many physical therapists fear that more children will fall through the cracks. This concern is related to the first two. Therapists argue that milestones being pushed later will result in children with delays being identified too late. Moreover, they worry that children who do not crawl will no longer be identified as having an atypical developmental trajectory. Concerns about decreased referrals have snowballed into broader concerns about fewer children qualifying for services and public or private funding sources declining reimbursement if children are not demonstrating delays relative to the CDC milestones.

We agree with Zubler and colleagues that due to clarifications and the 75% criterion, the revisions will increase, rather than decrease, the number of children referred for screening, evaluation, and services. Combined with the statement to Act Early and talk with your child’s doctor if the child is not meeting any of the clearly listed milestones, the updated checklists may stimulate more productive conversations between parents and their providers and simplify decisions about referral.

Clarifications in Interpretation of Updated Milestone Checklists

Based on a careful examination of the published changes and a consideration of current evidence in early childhood motor development, we contend that broad negative reactions to the updated materials are unwarranted. Here, we provide information meant to clarify, educate, and reassure those who are concerned about adverse consequences of the recent updates.

Implications of 75% criteria

In the revised guidelines, all skills are placed on the checklist corresponding to the age at which 75% of children would be expected to achieve the milestone. This cutoff was not applied to the prior version of the milestone checklists. Previously, there was not a consistent criterion for the placement of milestones at certain ages, and many were listed—often with ambiguous language such as “may” or “begins to”—at the average or median age of attainment. In other words, the checklists included some items that only 50% of children would have been expected to perform at the listed age. This change has resulted in some milestones being moved to later ages in the revised version. For example, “may be able to roll over from tummy to back” was listed on the old checklist at 4 months, whereas “rolls from tummy to back” is listed on the new checklist at 6 months. Similarly, “may take a few steps without holding on” at 1 year is now listed on the new 15-month checklist as “takes a few steps on his own.”

At first blush, the moving of select milestones to older checklists may seem like a substantial change. But this modification does not reflect standards for children’s development being lowered. It simply represents a repackaging of the information into a more useful format. A list of median ages of milestone attainment is useless for identifying delays that require clinical assessment and intervention.²⁶ We certainly would not expect to refer a child who was slightly below average in demonstrating a given milestone; by definition, we would expect half of the population to fall into this category! A 50% criterion therefore encourages precisely the “wait and see” response that many critics of the updated milestones fear. Conversely, seeing a child fail to meet a milestone that 75% of their peers have met would be of greater concern. If the updated surveillance system is applied as designed, such a child would be immediately referred for screening to determine whether further assessment and intervention are needed. In other words, the new guidelines should increase, rather than decrease, the number of children screened for services.

It is important to note that surveillance milestones do not affect children’s qualification for developmental services. The validated screening and assessment tools that physical therapists and other early intervention providers employ are unaffected by these updates and will continue to be the primary sources of information for intervention justification. Furthermore, children with additional risk factors due to medical or social history will continue, as always, to receive additional monitoring and screening. This process is unaffected by the changes to the CDC surveillance milestones, as surveillance is meant to identify children from the general population who might not otherwise receive monitoring.

The great crawling debate

Crawling was removed from the milestone checklists due to the dearth of normative data, inconsistency in definitions of crawling, variability in timing of crawling onset, and lack of evidence that all typically developing children crawl (Jennifer Zubler, MD-consultant to CDC, email communication, March 31, 2022). Here, we briefly review what is and is not known about crawling and early independent mobility in infant development.

Early theories of motor development emphasized neuromaturation as the driver of developmental change.^27,28 This view postulates that motor skills are expressed in a uniform, obligatory order, with each new skill building on earlier developing skills. In particular, crawling on all fours was seen as a necessary developmental precursor to walking. However, more modern approaches that emphasize variability and flexibility as hallmarks of typical motor development have de-emphasized the developmental importance of crawling.²⁹

Crawling is a wildly inconsistent motor milestone. Unlike sitting, reaching, and walking, which are functional skills into adulthood, crawling is a transient phase—a temporary solution for infants who are motivated to move but lack the postural control for upright mobility. Pre-walking mobility takes a plethora of different forms, from traditional hands-and-knees crawling/creeping, to hands-and-feet-crawling, to a variety of styles of belly crawling, to infants who scoot or roll or develop other idiosyncratic ways of moving independently to explore their environment.^30,31 And for some infants, upright cruising or walking is the first form of mobility, with crawling entering the repertoire later to solve functional problems such as retrieving a toy from under a table. Moreover, caregivers in some cultures actively discourage infants from crawling; as a result, infants in these cultures are far less likely to demonstrate the crawling milestone.^32–34 This inherent variability within and between cultures limits the usefulness of crawling as a milestone for widespread developmental surveillance.

Is crawling important for development? Current evidence suggests that, contrary to the predictions of neuromaturational theories, crawling experience does not contribute to the development of functional walking.^35–37 However, some therapists claim that crawling is necessary for the development of perceptual, cognitive, and fine motor skills in infancy and childhood. Classic theories regarding the role of crawling experience in building developmental skills are largely unsubstantiated by empirical research. Certainly, there is a considerable body of literature describing changes in sensory, cognitive, neurological, and social/emotional development when infants start to crawl. For example, crawling infants demonstrate improved mental rotation ability,^38,39 more flexible memory retrieval,⁴⁰ greater avoidance of a visual cliff,⁴¹ and increased sensitivity to peripheral optic flow^42,43 compared with prelocomotor infants. Crucially, however, these findings do not support the specific importance of crawling per se, but of experience with independent mobility. In fact, many of these results have been replicated in pre-crawling infants provided with precocious locomotor experience using a baby walker or a powered mobility device.^41–43 Empirical studies investigating differences between individuals who crawled and those who never crawled are rare; a comprehensive literature search turned up only three published articles of questionable quality^*.^44–46 As a final point, several studies investigating the transition from crawling to walking suggest that upright mobility provides numerous advantages over crawling for exploration and social interaction.^47–52 Overall, the literature on crawling does not substantiate its role as an essential motor skill.

In sum, evidence is lacking to strongly support the absence of crawling as a marker of atypical development at a specific age, or the therapeutic practice of encouraging crawling at the cost of other forms of mobility. The evidence most strongly supports the role of independent mobility for promoting global developmental outcomes. We note that the importance—or unimportance—of crawling is not settled science. We invite the physical therapy community to thoughtfully consider the current evidence and pursue new research to address this important question in an unbiased, scientific manner.

The more things change…

The outcry regarding the revised guidelines focuses primarily on the milestones that have been changed. However, a careful comparison of the old and new checklists reveals that a large portion of the motor milestones, particularly those in the infant and toddler years which have received the most attention, have remained the same, with only small changes in wording for clarity and decreased redundancy (Table 1). Despite rumors that the age of walking has been increased, the milestone “walks alone” (now clarified as “walks without holding on to anyone or anything”) was always listed on the 18-month checklist. Similarly, holding the head up in prone remains on the 2-month checklist, pushing up on elbows in prone remains on the 4-month checklist, sitting without support and getting into a sitting position remain on the 9-month checklist (note that the original version had an additional milestone of “begins to sit without support” at 6 months which has changed to “leans on hands to support himself when sitting” in the updated version), and cruising remains on the 1-year checklist. As the new guidelines become more ubiquitous, it is important to accurately represent the content of the 2004 guidelines and avoid misinformation about changes that were not actually made.

Developmental Surveillance and Physical Therapy

Although physical therapists are movement experts, the current US model of primary healthcare does not place us on the front line of population-based developmental surveillance. The CDC, with assistance from the American Academy of Pediatrics, designed surveillance guidelines to align with routine, reimbursed and preventative “well-child” care within the context of the medical home.² As such, pediatricians, nurse practitioners, and nurses typically start the conversation; for families at higher sociodemographic risk, home visitation professionals may also facilitate observation and discussion.⁵³ Until physical therapy is embraced as an integral part of routine, well-baby care—as in some parts of the world⁵⁴—our role within the general pediatric population remains with diagnostic screening and evaluation of infants who are referred by primary healthcare professionals or referred by early intervention or school-district personnel to determine eligibility for services under IDEA.

What, then, is the physical therapist’s role in developmental surveillance? Just as we expect primary care providers to recognize our expertise in providing developmental evaluation and intervention, we can support primary care providers in implementing the updated surveillance guidelines. The recent updates provide an opportunity to initiate or reestablish lines of communication between therapists and our referral sources. We can help to educate primary care providers about the new materials, emphasize the importance of providing referrals for children who do not meet milestones, and offer our clinics and early intervention programs as referral targets. In doing so, we can solidify interdisciplinary relationships, improve the efficiency of the referral process, and increase the availability of services for children who need them.

Note that there are three areas where physical therapists may be more directly involved in developmental surveillance: the neonatal intensive care unit (NICU), the primary provider model of early intervention, and community outreach. Physical therapists in the NICU or in NICU follow-up programs address preventative care by screening for and identifying developmental risks with infants born preterm or with other known developmental risks.⁵⁵ Physical therapists provide parents with resources to promote developmental monitoring, i.e. surveillance, and connect them with community-based or home visitation follow-up programs. Again, our role is not at the level of general, population-based surveillance, but for groups of children with known risk. Additionally, in early intervention settings where a primary service provider model⁵⁶ is used, physical therapists may perform surveillance for other developmental domains. A physical therapist serving as the primary provider for a child with a motor delay may become a front line professional in surveillance of cognitive, language, or social-emotional development. Evidence-based surveillance milestones for non-motor domains are crucial to help physical therapists monitor and facilitate conversations about appropriate cognitive, social, behavioral, and language development. Finally, physical therapists are increasingly becoming involved in community outreach programs such as childbirth education and parenting classes. This may provide an additional opportunity for educating parents about the resources available for developmental surveillance.

As practice patterns evolve, physical therapists may have additional roles to play in developmental surveillance. The provision of a robust tool like the CDC’s “Learn the Signs. Act Early.” program is a starting point for further discussions and professional growth regarding the identification of children who require our services.

Conclusion

Pediatric physical therapists are indispensable members of an interdisciplinary healthcare team. We help children and their families thrive as they navigate chronic diagnoses, acute injuries or surgeries, and developmental delays; we promote independence, participation, and quality of life. The CDC’s updated developmental surveillance tools have the potential to bring new families into our clinics and early intervention programs for formal assessment, increasing our reach and relevance and improving pediatric care. Pediatric therapists can unite to support these new families, helping them understand the difference between the surveillance that brought them to physical therapy and the diagnostic assessment necessary to determine the need for physical therapy and build a subsequent plan of care. Our profession can grow through collaboration with parents, caregivers, and our primary care partners as we Act Early together.