Developmental milestones

While children may develop at a different pace to their peers or have varying rates of

progress for one skill area compared to another, delays in achieving milestones may

affect their capacity to fully engage in activities such as play and education - and

could indicate a more serious underlying issue. Typically, whether or not a child is at

an age-appropriate level of development is considered under separate skill sets: gross

motor (using arms and legs), fine motor (using hands and fingers), speech and

language, and socio-emotional development. ‘Self-care’ skills – such as being toilet-

trained – also feature commonly in assessments of developmental status, especially in

the context of the child spending more time outside the home, for example, starting

pre-school.

Presence of an intellectual disability (ID) is one of the outcome indicators used in the

State of the Nation’s Children report (DCEDIY, 2024b). According to the most recent

report, using data from the National Ability Support System, 5% of children registered

as having an ID in 2022 were under 5 years old – equivalent to a rate of 1.5 per 1,000

based on population estimates. For all childhood cases, ‘mild’ or ‘moderate’ ID

15 Note that medical card coverage includes the cost of the child’s prescriptions, unlike the universal GP visit scheme for all under 8’s which covers the cost of GP visits, but not prescritions

accounted for over half of cases but over a third were described as ‘not verified’

(p.89).

As questions on developmental milestones are very much tied to the age of the child,

the following paragraphs discuss the measures used with Cohort 08 at 3 years:

Gross motor skills were estimated using a combination of questions to the primary

caregiver and direct observation by the interviewer. The primary caregivers were

asked whether the child could ride a tricycle, and a retrospective question on the age

at which the child had taken their first steps. The interviewer observations involved

asking the child to stand on one leg and throw a ball overhand.

Fine motor skills for Cohort 08 at 3 were estimated by (a) asking the parent a

question on whether the child could play with small pieces such as Lego or a jigsaw

and (b) two interviewer observations. These latter involved asking the child to copy a

straight vertical line drawn by the parent and observing how they held the pencil

while doing so.

Questions to the parent on development of self-care skills asked specifically about

the continued use of nappies or ‘pull-ups’, and the use of a ‘soother’ or ‘dummy’.

There were no observations by the interviewer.

The parent was asked about any concerns in relation to the 3-year-old’s speech. This

was a ‘tick all that apply’ format and included response options such as a lisp or

stammer, and ‘difficulty finding words’. If the parent did have a concern, there was an

additional question on whether the child had received any treatment for it.

The child’s cognitive ability – specifically their expressive vocabulary and reasoning

skills – were directly assessed by the interviewer using standardised tests from the

British Abilities Scales. These are described in more detail in Chapter 6 on

supplemental measures.

It would be very useful to repeat the Cohort 08 measures with Cohort 24 at 3 years

to explore whether the current generation of toddlers are generally progressing at

the same rate of development as their peers fifteen years previously. The items

would, of course, also be useful in assessing the development of Cohort 24 cross-

sectionally – and the extent to which being ‘on time’ or delayed in a particular area at

age 3 affects their outcomes at older ages.

There are, however, standardised measures of development that could be used for

Cohort 24 at 3 years instead of repeating the individual questions and observations

used with Cohort 08 at 3. The main contender in this space would be the Ages and

Stages Questionnaire, given that a version of this measure was also used with Cohort

24 at 9 months.

Ages and Stages Questionnaire – 3rd edition (ASQ3, Squires & Bricker, 2009)

The ASQ3 is a standardised measure of development in the form of a questionnaire

to parents. It covers development in the areas of communication, gross motor, fine

motor, problem solving, and personal-social. The questions ask the parent if their

child can perform certain specific tasks – for example, ‘Does your child stack three

small blocks or toys on top of each other by herself?16’. The primary caregiver may

have already observed the child to perform some of the tasks, but other tasks could

be so specific that the primary caregiver will need to do the task with the child before

they can answer the question. This will have implications for the time in the home if

the ASQ3 is completed with the interviewer; consideration could be given to leaving

it with the parent to return by post but this is likely to result in a substantial number

of missing responses.

The ASQ3 is available in an age ‘36 months’ version which should be suitable for

Cohort 24, assuming that the interviews are scheduled for the child’s actual 36th

month (as was the case for Cohort 08 at age 3). Two further arguments in favour of

using the ASQ3 with Cohort 24 at 3 years are: (a) a version of the ASQ was used with

Cohort 24 at 9 months and (b) the ASQ3 is used by public health nurses in Ireland to

perform developmental checks – although clarification would be needed as to how

often the 36-month version specifically is used.

16 This is a sample item from the instrument for 16-month-olds as per the publisher’s website: https://agesandstages.com/wp-content/uploads/2015/02/asq-3-16-month-sample.pdf

Recommendations for Cohort 24 at 3 years:

•Explore whether it would be feasible for the parent to complete the ASQ3 at 36 months old with the interviewer present

•If using the ASQ3, repeat any additional questions from Cohort 08 at age 3 that are not covered by the ASQ3 – such as the retrospective question on age of taking first steps

•If it is not feasible to administer the ASQ3, repeat the questions and interviewer observations as used with Cohort 08 at 3

Child measurements