Just a couple of random comments - on animal studies, they can give much higher doses than they can to humans, so if there are problems with the substance being studied, it will show up much sooner in the animal studies than in the human ones.

Regarding the infertility question, there's also the phenomenon (as I see it anyway) that the more affluent tend to have their children later, which gets increasingly difficult for biological reasons. (Not to rule out the chances of effects of bottle vs breast feeding, though, on fertility or many other things.)