Growth Charts Schmoth Charts

I think that the thing that gets the worst rap from the breastfeeding community is probably formula, but really it should be growth charts. Growth charts don't seem to bother formula feeders much and what it boils down to is the issue of control. It is very easy to see how much formula a baby drinks, and so if weight gain doesn't meet some lofty ideal, not getting enough milk is easily ruled out.

Boobs don't come with a built-in metering device, meaning that input is completely unmeasurable. In a culture that trusts information over instinct, breastfeeding parents are left to measure output for peace of mind. New parents, fathers in particular, don't do well with disposing of direct output, let alone weighing it, so instead we measure indirect output by popping our get on a scale and plotting their weight on a weight-for-age chart.

Consider Baby A: Born at 40 weeks on the dot, weighing a lovely average 7 lb, 100% formula fed on demand, milk input carefully logged, maintains a steady growth through the first six months and weighs in at 14 lb. Great job, big pat on the back. After 6 months, solids and water are introduced, baby starts to crawl, pull up, cruise, sleeps for ages at night and weight gain remains perfectly on track for 21 lb at 12 months. Ah what beautiful sense it all makes.

Now Consider Baby B: Born at 41.5 weeks weighing nearly 10 lb, 100% boobfed on demand, grows like a Russian body builder on steroids and doubles birth weight by a mere 4 months. His weight on the growth charts was always above the top line, but continues to diverge. By 6 months baby is crawling, pulling up, cruising and waking every 2 hours for a suck and getting in loads of delicious hind milk and not at all interested in solids in any shape or form. By 12 months baby is only 2.5 times birth weight, below the top line on the chart, still waking for milk every 3 hours at night and has only just showed an interest in solid food. None of it makes any sense at all.

Or does it? Breastfed babies often gain weight very well in the first 4-6 months. That is to say, they gain weight well compared to healthy formula fed babies, which thanks to lots and lots of data seems to have become some kind of yardstick. It makes a lot of sense that breastfed babies should gain more early because breastmilk is used almost 100% efficiently and their stomachs are very small. For the same milk volume, an infant digestive system is able to make more productive use of breastmilk.

After six months, tummy volumes have increased and solid food comes into play, so the playing field starts to level off. Breast and formula fed babies seem to end up in the same place by 12 months, but their paths to get there are often quite different.

I find it puzzling that people think they have control over their baby's weight. Traditional guidelines such as "double by six months, triple by twelve" are based on birth weight, which really is based on gestation period. In the final trimester, your little one gains about half a pound a week, so the difference between being born at term (37 weeks) and two weeks overdue (42 weeks) is a whopping 2.5 lb. By 6 months that's 5 lb and by 12 months that's 7.5 lb, which seems unlikely to me.

At some point a baby moves away from its growth pattern being determined by its birth weight and begins to follow the growth pattern that will see it end up in its adult size. It makes sense to me that this point is somewhere in the middle part of the first year, when the baby has gained enough weight for survival purposes. A baby may make a jump across several weight-for-age percentiles in either direction, depending on birth weight and adult size. This means that growth charts really are not a reliable means of measuring how well a baby is doing, which is not surprising considering early humans didn't have scales or statistics.

The most reliable indicator of whether your baby is thriving is whether your baby is happy, healthy, making progress towards milestones... colic, child care viruses aside, of course. Good news for those of us who like to measure things is that the WHO even has a gross motor milestones for age percentile chart!