New study of a decade s worth of Florida births seems to show heavier newborns do better in school up to 10 pounds

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Think newborns should be slim and trim? Think again. A very large study evaluating children s health and intellectual status as a function of birth weight found that heavier babies do better in school, with 10 lbs. being optimal.

Happy Baby, Happy MomA draft study, to be published later this year in American Economic Review, assessed school-age children s weight at birth and its relationship to later cognitive achievements.

The lead author, David Figlio, PhD, of Northwestern University and director of the Institute for Policy Research, and three co-authors, followed all children born in Florida between 1992 and 2002 (over 1.3 million singleton births and almost 15,000 twin pairs) to assess the link between birth weight and school performance based on an amalgam of measurements from birth until middle school.

A simple graphic (which we are unable to reproduce here) demonstrates the relationship quite clearly: the cognitive accomplishments rise gradually from a birth weight of 3 lbs. up until a weight of 10 lbs then declines, descending to below-average (50th percentile) at around 11 ½ lbs.

Dr. Figlio told the New York Times that their study does not mean that birth weight is destiny. Its effects are considerably smaller than those of social class, for example. A lighter baby of well-educated parents is likely to do much better in life than a heavier baby of high-school dropouts.

Yet within every group the researchers studied, birth weight appeared to have a noticeable effect, even after controlling for a long list of other factors.

Dr. Figlio estimates that, all else equal, a 10-pound baby will score an average of 80 points higher on the 1,600-point SAT than a six-pound baby. Another way to see the pattern is to look only at top-scoring students: Among the top 5 percent of test scorers in elementary school, one in three weighed at least eight pounds at birth, compared with only one in four of all babies.

The authors make critical note of the trend in our nation to intervene medically when the thought that doing so might be of some benefit even when the data to support those interventions is scanty, absent, or even (as in the case of early induction of labor or c-section) contradictory.

ACSH s Dr. Gil Ross had this comment: We here at ACSH have noted on several recent occasions the newer data showing that the last 2 weeks of gestation are important, and not disposable as had been thought. Both maternal and neonatal outcomes are better at full-term delivery, and induction/c-section should not cavalierly be performed before 39 weeks unless medically required.

Now, we learn that longer gestations and larger newborns have an advantage over their first 10 years or more in academic achievement. So we doctors, parents, moms-to-be should get the message and let nature take its course, in this case anyway.

ACSHs Ariel Savransky adds, However, it s also important to pay attention to the other end of the spectrum. Parents should be cognizant of weight gain in infancy, as it s more likely that an obese child will be obese as an adult.