Complex sentence: Despite the insignificance of birth defects found in Neel's study and the detailed medical literature, up to 1987, historians such as Ronald E. Powaski frequently wrote that Hiroshima experienced "an increase in stillbirths, birth defects, and infant mortality" following the atomic bomb.
Split into simpler sentences: Despite the insignificance of birth defects found in Neel's study and the detailed medical literature. Up to 1987, historians such as Ronald E. Powaski frequently wrote that Hiroshima experienced "an increase in stillbirths, birth defects, and infant mortality" following the atomic bomb.