If you are concerned about getting extra doses of estrogen, I wouldn't discount the effects of phyto-estrogens such as that found in soy based products. As reported in the Lancet "babies fed soy-based baby milk take in such large amounts of estrogen-like chemicals found in soy beans, that they are exposed to doses six to 11 times higher than those known to have hormonal effects in adults, The concentrations of phyto-estrogen in babies given soy-based milk are 13,000 to 22,000 times higher than the normal estradiol concentrations for babies, and therefore, the researchers conclude that they must have some biological activity in the infant".