14 Mar 2018 --- Baby girls who were fed soy-based formula have subtle changes in the cells and tissues of their reproductive system when compared with infants fed with breastmilk or cow’s milk. This is according to the researchers at the Children’s Hospital of Philadelphia, who stress that although the differences are subtle and not a cause for alarm, they do point to the need for further research. The study investigated the postnatal development of estrogen-responsive tissues, along with specific hormone levels, according to the infant feeding practices.