title: The authors reply.
authors.affiliation: Department of Pediatrics, Faculty of Medicine, McGill University, Montreal, QC, Canada Department of Epidemiology, Biostatistics and Occupational Health, Faculty of Medicine, McGill University, Montreal, QC, Canada.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kramer
authors.affiliation: Department of Pediatrics, Faculty of Medicine, McGill University, Montreal, QC, Canada.
authors.forename: Xun
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Pediatrics, Faculty of Medicine, McGill University, Montreal, QC, Canada Department of Epidemiology, Biostatistics and Occupational Health, Faculty of Medicine, McGill University, Montreal, QC, Canada.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Platt
mesh_terms: D003627:Data Interpretation, Statistical; D015340:Epidemiologic Research Design; D005260:Female; D005865:Gestational Age; D006801:Humans; D054238:Perinatal Mortality; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*; D050497:Stillbirth