120 (6): 1337–1351. doi:10.1213/ANE.0000000000000705. PMC 4438860 . ↑ https://www.ncbi.nlm.nih.gov/books/NBK11385/ ↑ https://www.nytimes.com/2015/05/07/health/premature-babies-22-weeks-viability-study.html?_r=0