In Vitro Fertilization Should Have One-Embryo Limit, Health Experts Say A new study led by Keith Barrington, chief of neonatology at Sainte-Justine UniversityHospital in Montreal, has measured how extreme the causation is: While IVF accounts for only 1 percent of Canadian births, 17 percent of babies admitted to the neonatal intensive care unit (NICU) where Barrington works were IVF babies. An American doctor confirmed that the numbers are similarly disproportionate in the United States. In his paper, published in the upcoming Journal of Pediatrics, Barrington advocates legal intervention to reduce the risk.