most of the American studies on NFP were conducted by the program’s own developer
Not ideal?
This is a great example of the use of understatement if there ever was one. I'd say such a conflict of interest would put the credibility of the entire study at risk.
>The study also focused on young moms, using their youth as a proxy for low income, so its subjects might have been less disadvantaged than their American counterparts to begin with.
The article does mention that similar programs did show good results in the Netherlands and Germany (if at a smaller scale than in the US). I don't think the article really answer the question it raises. It seems odd that you would keep smoking or drink just because you have universal healthcare. It that was the case it would indicate that we care more about our finances that our health (which might be true).
One reason the U.K. results were so lackluster might be that the Lancet study compared home-visiting to “usual care,” or the health care new moms would receive anyway. But since the U.K. has universal health care and the U.S. does not, it could be that there was less of a difference between the two British groups than the two American ones.