World Little, tiny baby? Ryusuke Sekino of Japan was just over half a pound. Now he’s going home April 19, 2019 Yuri Kageyama, Associated Press Comments Off on Little, tiny baby? Ryusuke Sekino of Japan was just over half a pound. Now he’s going home The University of Iowa keeps a Tiniest Babies Registry. The previous smallest surviving boy weighed 9.5 ounces when he was born last year in Japan.