mbachur, I wouldn’t worry. This from abcnews:
The report from the American Academy of Pediatrics also referred to theories that some of the hormones in soy protein formulas can interfere with an infant’s reproductive development because of their similarity to the human hormone estrogen. But no studies have supported these ideas.
That report recommends milk based formula, because there is “no reason” to use soy. Well, we have a good reason, so I don’t know if a posek would say to use chalav stam based on unsubstantiated theories. I certainly wouldn’t worry about it after the fact.
Does anybody have any real studies showing a problem with soy?