2641674 ELBW extremely low birth weight 1286 2641671 ELBW extremely low birth weight infants 56 2641675 ELBW extremely LBW 3 2641676 ELBW extreme LBW 2 2641677 ELBW ELBW children 1 2641672 ELBW extremely low birth 1 2641673 ELBW extremely low BW infants 1 2641669 ELBW extremely low-birth-weight preterm infants without 1 2641670 ELBW extremely premature newborns 1 2641668 ELBW extremely preterm and low birthweight 1