Saturday, July 03, 2010

Baby BMI

I was startled to hear on the radio someone report the birth of a baby weighing over 8lbs – on the 82nd percentile. That means something like 1 baby in every 5 these days is more than 8lbs?

In my youth everybody knew that a normal full term baby weighed in at 7 lbs. One of the less attractive attributes of my mother & her friends – indeed of all the other women in the town - was the eager way in which they awaited the birth of a newly wed's first child – usually, or at least often, within a year of the wedding. Then the ‘Well, they say it’s a honeymoon baby, but it’s barely 8 months & it weighed 7 lbs!

News of an eight pound baby made everybody’s eyes water.

I had noticed that babies born to readers of The Times – at least those whose birth is announced in the expanded version of the column which now comes complete with photo of the new arrival & too much information (what the mother was doing when her waters broke, for heavens sake) – often weigh in at closer to 9 lbs, but these are the most affluent & well nourished section of the population. The mothers are also much older, taller & heavier than those of my mother’s generation.

I found figures for 2005 in Table 5 of Birthweight and gestational age by ethnic group.

Looking just at the category White British (the sort that my mother's generation would have been thinking of) I was slightly relieved to see that the average for a full term baby is still under 7 ½ lbs, but still almost one baby in eight weighs in at a wince-inducing 8.8lbs.

We are used to hearing that low birthweight is a Bad Thing, but does anybody even try to calculate the BMI for a baby & make pronouncements as to what is the healthy number? Is there any evidence that White British babies are getting longer as well as heavier? Are the heaviest babies born to the tallest women? Does obesity start in the womb? I think we should be told.

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