Leaders of the US National Children's Study have released a revised design for the ambitious effort to track influences on the health of 100,000 American children from before birth to age 21. An earlier proposed revamp, designed to cut costs, had been criticized for its selective sampling method; the new proposal, released on 24 July, would enrol women from birthing hospitals across the country, creating a sample representative of the US population. To cut costs, it would track only some 60% of participants while they are in the womb. The US Congress may require a report from the Institute of Medicine before any changes are made to the current design.
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