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A whole host of studies have offered important insights on how health in the early years influences adult outcomes.

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Children are less healthy at birth when they are born to low income families.

It is well known that humble beginnings are a handicap, argues Janet Currie of Princeton University.

In a presentation made to the annual meeting of the Canadian Economics Association, held over the weekend at the University of Calgary, she suggested that extensive research also documents the causal impact of low birth weight and has policy implications for not only the poor, but also the rich.

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If low birth weight causes low socio-economic status in adulthood, rather than just being associated with it, then there is a strong case for public policy to be concerned about the well-being of low income women in their childbearing years.

But this causal relationship also raises cautions about in vitro fertilization, generally used more by the relatively well-to-do, and also more likely to lead to infants with lower birth weights.

She said, "from the perspective of child health it is very dubious to be subsidizing in vitro fertilization. It will lead to much lower child health."

In 2010 Quebec became the first jurisdiction in North America to support in vitro fertilization through the public purse. But the procedure has a tendency to lead to multiple births and, even when it doesn't, to lower birth weight. This, in part, is the basis for Prof. Currie's comments.

The Canadian-born Prof. Currie offered an overview of an extensive academic literature examining the relationship between the socio-economic status of mothers and the birth weight of their children, showing that:

1. There are large inequalities in health at birth with women of lower socio-economic status having children with lower birth weights;

2. Lower birth weight predicts important outcomes like schooling attainment, labour market engagement, and reliance on social assistance in adulthood;

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3. The transmission of poverty across the generations should not be considered as genetic, even though girls with low birth weights grow up to in turn have low birth weight children;

4. There may be remedial policies that can reverse this intergenerational cycle of low health and socio-economic status.

These patterns exist across many of the rich countries, whether or not they have public health care. Poor children are more susceptible to risks that adversely influence their health, even though they may have more access to hospitals and health care in some countries than in others.

Dr. Currie is particularly concerned with dispelling the idea that these risks are genetic. "To say something at birth is genetic is code for saying we can't do anything about it." She suggests that biologists increasingly feel that environmental factors determine how genes are expressed, and that therefore the distinction between nature and nurture is a false dichotomy.

She points out that maternal education plays an important role in determining birth weight.

For the most part this channel works through the impact more education has on lowering smoking, and thereby improving the in utero environment.

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A whole host of studies -- some of the most convincing being done using administrative data from Manitoba -- have offered important insights on how health in the early years influences adult outcomes.

Differences between siblings in education, the use of social assistance at age 17, height, IQ, full-time earnings, and even the intergenerational transmission of low birth weight, have all been shown to be determined by differences in birth weight.

And these studies also show that the impact of birth weight is much smaller when children are born in higher income families, and when low income families receive higher child benefits.

Miles Corak is a professor of economics with the Graduate School of Public and International Affairs at the University of Ottawa. A more detailed version of this post is available .

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