The 50th Percentile and Other Mythical Creatures



NOT THE SAME!!!!!!!!!!!!!!

Sorry for yelling, it’s just that pregnancy and new parenthood are such fragile times already without adding fear about our bodies or babies not being average. If care providers could just give a little context around percentiles and other markers of averageness, folks might not be so freaked out! Naturally occurring measurements that are above or below the average can still be normal.

So if normal and average do not mean the same thing, let’s explore their meanings. It took me three tries to pass statistics in university so I feel qualified and excited to explain.

Baby has a book

Statistics, amirite?!

Normal: “conforming to a type, standard, or regular pattern”, and “occurring naturally”. Whether you or your progeny are on the big side, the small side, or squarely in the middle, you are naturally occurring and therefore normal. It also means that the person has reached milestones or other developmental achievements within an expected span of time.

Average: “a single value (such as a mean, mode, or median) that summarizes or represents the general significance of a set of values”. For example, If we look at the weight or height of a large population of babies the average will summarize or represent all of those values in a single value. So now that I am having flashbacks to my first year in university, we can continue.

Twins twinning.

Just a couple of normal guys being normal.

So who is this average baby anyway? Who is this 50th percentile creature whose baby clothing size is their exact age in months and for whom all diapers seem to fit? I have no idea. But I have met hundreds of NORMAL babies. Babies with thighs for DAYS and babies with improbably long toes, babies born at 41 weeks weighing 6 lbs and 37 weekers weighing in at 8 lbs. The daintiest of daints and the chubbiest of chubs. Ones with long, luscious heads of hair, ones with less fuzz than a peach, and all of those in-between. Colloquially, average can be a stand-in for normal, which is where I think most of the confusion comes from. And while some of these babies were not average, they were definitely normal and healthy.

Occasionally, within this diverse group of normals, there are exceptions; Babies who are born very large or very small for their gestational age. There are also babies born before they reach full term who will have received extra attention as they grow, mature, and catch up to their peers.

These examples are rare and outliers like them help care providers define who falls within the range of normal and who does not, as well as some possible causes. The normal range we are left with is still quite big and diverse.

So you may be asking yourself now, if normal is so diverse, why bother comparing? Good question. By plotting the growth of a pregnant belly or an infant on a graph and comparing it to others, not only does this show whether or not the person’s growth is within the range of normal at that visit, but also allows them to follow the “growth curve” of the baby or belly. The most important comparison is not to others, but to one’s self. With some fluctuation, one would expect a belly, infant, or child to stay roughly within their percentile as they grow. And while growth spurts and plateaus happen, for most of us humans, it evens out quite predictably.For the first 2 weeks of life, an infant’s size and growth are scrutinized. This is because weight gain is the primary indicator of how well feeding is going. Then, it becomes a race to reach the predictable milestones and stay on the growth curve. This beginning of life measurement and the ensuing follow-ups can feel like a judgement or a points system. It’s not. If you or your kiddo is in the 5th percentile, it only means that most people are bigger. Not better, just bigger. And the key is looking at the growth trend. What if your child suddenly “fell off their curve”? Did they start crawling recently? Are they allergic to something? Is everything else normal and maybe they are just at a growth plateau? You and your child’s care provider will look at all of the factors, not just percentiles, to see if there is a cause for concern.

Basically, most average sized people are normal, but generally so are those above or below average.

And with all of the attention paid to your belly’s measurements during pregnancy, fetal measurements at ultrasounds, and then your child’s growth curve from birth through adolescence, it can feel overwhelming, frightening, and a little joyless sometimes. Whether you and your offspring are normal, outliers, or somewhere in-between, it’s so crucial to step back from the recreational comparing of ourselves and our children to others. This is why I absolutely love the article Jessi Cruikshank wrote for Flare about her beautiful, hilarious, non-walking, 17-month-old twins. You an read it here. She stepped back from the judgement and feeling of failure so that she could reconnect with the joy of parenting them.

It is rare that I tell people what to do or not do, but this feels different. We live in a culture that confuses value with size. For infants, parents may be hearing the message that “bigger is better” or “walking at 12 months is better”. For adults, the message is often that “thinner is better” ,“taller is better” and so on. Medical professionals need tools like graphs and charts to assess if there is cause for concern for our health, but these tools do not reflect our value or worthiness of love, respect, or inclusion. Whatever a person’s state of health, wealth, well-being, size, age, ability, ethnicity, or circumstance, and whether or not they fall within the range of normal in any respect, is not a requirement for fulfillment. So let’s leave the comparing to the professionals and get on with the very important business of enjoying our children and ourselves.

I’ll just leave you with this delicious example of  Chrissy Teigen and John Legend enjoying their son, Miles, adorable helmet and all. #Goals!