What do milestones really mean?

THE PERILS OF CHECKING MILESTONES
We look for new skills in our babies to see if they are developing well. We check the lists of “milestones” and match our baby’s skills to it. There are some things we need to keep in mind.  Obviously, I believe in the sequence of development. Obviously, I am contributing to the “milestone mania” by printing the lists of milestones on the pages above but I want to caution you to use them carefully.
MILESTONES ARE AVERAGES
A first and important issue is that milestone lists are based on average. This means that half of babies will meet the milestone before and half will meet the milestone a little later. Milestone lists can either be at the time after most children will achieve the skill or most common time. No baby is common so it will be a rare baby who hits all the milestones when they are listed. My favorite developmental screening tool (photo and more on testing later) actually lists the skills on a bar that crosses several age zones and starts when 1% of infants show a skill, has marks for when 25% and 50% demonstrate the skill and finishes when 90% of infants demonstrate the skill. If your child is anywhere on the bar when the skill begins it is within normal limits.

An example of The Denver Developmental Screening Test.

DEVELOPMENT IS NOT SMOOTH
A second factor is that development is not a smooth, even process. It occurs in fits and starts. Some babies will be at the same level for a period of time and then will jump in all areas. Others will make huge steps in one area of development while others rest. Most mothers notice and mention that there is a slowdown in speech when babies start walking. What this means is if you check your baby just before a development spurt he may seem behind but a week or two later just after a spurt, he may seem ahead.

DEVELOPMENT IS NOT EVEN PERFECTLY SEQUENTIAL
You have heard the old expression, “you can’t walk, until you crawl.” Well, technically that is not true. Roughly 12% of typically developing babies never crawl and go on to learn to walk at a typical age. They do tend to find a way to move forward, most by hitching while sitting, but not on their hands and knees. We go back and get these children to crawl after they have walked to get the benefit of crawling for their hands and arms and senses but it shows that crawling is not absolutely essential to motor development. The same applies in all areas of development. Your baby may skip a step or two here and there before achieving a higher skill and may go back later or may never pass some stages.
CULTURAL AND ENVIRONMENTAL ISSUES
Many of the items used to test milestones are based on cultural practices. For example, self feeding is often used as a measure of social development or of fine motor development. In some cultures, babies are not allowed to feed themselves at an early age and would have no experience with this.   Even children from other cultures, who have not been allowed to feed themselves perhaps because it is messy, would not be demonstrating this skill. Children may start to scribble on paper by about 15 months, but an infant who has never seen crayons or watched her mother or siblings color, is just as likely to put the crayon in her mouth as to mark paper without a demonstration. Some degree of experience is assumed in setting milestones as the majority of infants will have had it but not all.

PREMATURE BABIES AND MILESTONES
In order to understand this, we must remember that development starts at conception. A baby born at 40 weeks has been developing for 40 weeks but one born at 25 weeks has only had 25 weeks of development and still needs the extra 15. This means that, if your baby was more than 3 weeks early, you need to count that time for intrauterine development. When checking milestones, you need to use the due date and not the actual birthdate.  Most professionals will do this until your baby is 2 years old. It isn’t that he has suddenly gained that extra couple of weeks at 2. It is just that, by 2, there is so much variation in normal development that we no longer measure in months but in 3 to 6 month increments. I worked with children up to 3 years of age and I kept in mind any prematurity until then, when testing.
INFANT TESTING
Most infant testing is looking at development based on milestones. They tend to look at 5 areas of development, Gross motor, Fine motor (hand skills), Cognitive, Language and Social development.  The results of testing are impacted by all of the above.  More importantly, most infant testing has very poor predictive validity. This means that infant test tell you what your baby is like today. This is useful for doctors and people working with children and you for choosing suitable activities for your child but it is not useful to say anything about your baby’s future develoment. One reason for this is that infant brains are still forming and can change with the proper stimulation. There are several types of testing and most milestone charts fall into the category of screenings. These tests may suggest that there may be a delay but a more complete test would be needed to confirm that. Further testing is much more involved and needs to be done by a specialist. Some delays are due to environmental issues. Babies cannot learn to crawl if they are not on the ground, for example. These can usually be corrected with changes to the environment. Others have their roots in physical causes and may be life-long but all infants can make some progress with early intervention.

WHEN SHOULD YOU BE WORRIED
According to the Denver Development Screening Test, you should not be worried until you baby has not demonstrated 3 or more of the skill bars that are fully completed below her age range or, for premature babies, adjusted age.  This means that your baby may not show one or two of the skills at age level on a milestones list but that should not cause concern. If your baby is not demonstrating most skills that are 2 months behind his age in any area, you may want to consult your doctor. In any case, never be afraid to bring up your concerns to your pediatrician. You live with the baby. The pediatrician only sees the baby for a few minutes every few months, and usually the baby is distressed simply by being handled by the doctor. They can tell a lot from the weight and height and medical measurements but need your input on daily development issues under normal circumstances. Bringing up your concerns will, at the very least, give you some relief as the pediatrician can reassure you or refer you for help, whichever is needed.