Complex sentence: During pregnancy, the placenta converts the hormones DHEA and DHEA sulfate to the estrogens estrone and estradiol, respectively; after these estrogens are produced by the placenta, the estrogens are transferred into the baby's circulation thereby producing temporary gynecomastia in the infant.
Split into simpler sentences: During pregnancy, the placenta converts the hormones DHEA and DHEA sulfate to the estrogens estrone and estradiol, respectively. After these estrogens are produced by the placenta, the estrogens are transferred into the baby's circulation thereby producing temporary gynecomastia in the infant.