Oxford English Dictionary. ↑ New Oxford Dictionary of English. ↑ American Dictionary of the English Language, Noah Webster, 1828. ↑ "Fetal development: MedlinePlus Medical Encyclopedia". www.nlm.nih.gov. Archived from the original on 2011-10-27. ↑ Institute of Medicine of the National Academies, Preterm Birth: Causes, Consequences, and Prevention Archived 2011-06-07 at the Wayback Machine.