You need to compare maternal obesity rates, not mean BMI. The two are not correlated because there are major biases in maternal demographics. For instance in th

You need to compare maternal obesity rates, not mean BMI. The two are not correlated because there are major biases in maternal demographics. For instance in the US most children born are now non-white and there is a strong inverse correlation between income and fertility rates. Both those characteristics (non-white, low income) in turn correlate strongly with increased obesity rates. There are an immense number of studies on this topic. Without link bombing an easy way to find more data is to check out google scholar: https://scholar.google.com/scholar?q=US+infant+mortality+obesity https://scholar.google.com/scholar?q=US+infant+mortality+obe... Something that might help clarify matters most is this [1] paper. It not only gives specific figures but is over an extremely large and comprehensive sample, most of the data is from a ethnically homogeneous sample, and is in a region with nationalized healthcare (Sweden). So it helps remove confounding variables. And there too we find that infant mortality for normal weight women was 2.4/1000 while it was 5.8/1000 for those with obesity grade 3. There was a linear scaling of risks and mortality that mapped directly against obesity. Interestingly enough even being just overweight also corresponded to a slightly increased rate of infant mortality. Crucially, what obesity tended to lead to was preterm deliveries, congenital birth defects, pregnancy complications, and sudden infant death syndrome. The reason I say crucially is that these [2] are the leading causes of infant death from the CDC. Those issues that arise from obesity are literally the top 4/4 causes of infant death. [1] - https://www.bmj.com/content/349/bmj.g6572.full.pdf+html https://www.bmj.com/content/349/bmj.g6572.full.pdf+html [2] - https://www.cdc.gov/reproductivehealth/maternalinfanthealth/infantmortality.htm https://www.cdc.gov/reproductivehealth/maternalinfanthealth/...