Two recent articles explore the long-run effects of maternal weight gain and/or high weight at birth on long-run outcomes. Much of the health economics literature has focused on understanding returns to birth weight at the lower tail of the distribution, and several studies have found notable effects of birth weight on wages, schooling and cognition later in life. The downsides to high birth weight have been explored in the medical literature, which has typically focused on obesity and diabetes risk among children born to diabetic mothers (who birth larger than average - or macrosomic - infants).
A recent study in Obstetrics and Gynecology illustrates that increased gestational weight gain among mothers is associated with higher risk of obesity among their offspring. Unlike past studies, the study sample here is not limited to mothers with diabetes. While causality is difficult to establish here - mothers that gain weight during pregnancy may have similar preferences/constraints regarding food, which can be passed on to the next generation via other means besides biology - the results are interesting and deserve further research attention.
In a recent NBER working paper, Resul Cesar and Inas Rashad look at the association between birth weight and cognitive outcomes among a sample of children and teens and young adults followed in two different panel studies. The main result is that birth weight is associated with lower cognitive test scores at both the low and high part of the distribution: heavy infants suffer deficits, too.
I'm guessing this literature will likely explode in the next few years, especially with the ever growing obesity "epidemic" and its obvious consequences for maternal weight during pregnancy (see here for an earlier piece on this). Hopefully, this literature will address two major areas:
(1) Causal effects - Spatial variation in food prices, dynamics from recessions, the introduction of public programs and other shocks can be used to identify maternal weight gain during gestation and child birth weight. Utilizing this variation can help eliminate from the picture alternative interpretations of the association between maternal weight gain, child birth weight and later child outcomes.
(2) Mechanisms - Even if you can recover causal effects, what is the pathway? A link between high birth weight and lower cognition could be biological in nature or may operate through reduced and less effective investments in childhood and adolescents due to diminishing social returns to body weight: kids may learn less effectively if they are being made fun of at school for their appearance. These explanations have vastly different policy implications and should be teased apart.
4 comments:
Atheen,
I think that there is an argument that food prices aren't exogenous, even though most of the obesity literature ignores this fact (but that might be due to a lack of good instruments).
I fully agree on the food prices, and even the institutional characteristics (though changes in food taxes and such might have better properties).
At the very least, I think it would be a start in the right direction. And there are new methods out there that allow for one to test the sensitivity of the results to varying degrees of violation of the IV exclusion restriction.
I wonder if theres any high birth weight cutoff to do an RD here.
I think there is a HBW cutoff (4500 grams?), but I am not sure about its potential for identification - that is, its not obvious to me that physicians act differently around this threshold. However, if people take the papers in this post to heart, such differential behavior might come to exist...
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