Compared with feeding infants breast milk or cow-milk formula, soy formula feeding does not affect subsequent reproductive organ size at 5 years of age.

BACKGROUND Literature reports suggest that phytochemicals, such as isoflavones found in soybeans, impair reproductive function in animals and raise the possibility that consuming soy infant formula could alter hormonally sensitive organ development in children. OBJECTIVE This study compared reproductive organs volumes and structural characteristics in children at age 5 y who were enrolled in the Beginnings study long-term cohort. METHODS Breast bud, uterus, ovaries, prostate, and testes volumes and characteristics were assessed by ultrasonography in 101 children (50 boys and 51 girls) aged 5 y who were breastfed (n = 35) or fed cow-milk formula (n = 32) or soy formula (n = 34) as infants. Analyses were adjusted for race, gestational age, and birth weight. RESULTS Among girls, no significant differences were found in breast bud, ovarian, or uterine volumes; counts of ovaries with cysts; ovarian cysts numbers; ovarian cyst size; and uterine shape between the diet groups. Among boys, no significant differences were found in breast bud, testes, or prostate volumes or structural characteristics between the diet groups. CONCLUSIONS In this cohort, no early infant feeding effects were found on reproductive organs volumes and structural characteristics in children age 5 y. The follow-up of these children through puberty is planned and should help delineate potential early infant feeding effect on reproductive function later in life.