title: The Effect of Birth Order on Neonatal Morbidity and Mortality in Very Preterm Twins.
abstract: ObjectiveThis retrospective cohort study examined the effect of birth order on neonatal morbidity and mortality in very preterm twins.Study DesignUsing 2005 to 2012 data from the Canadian Neonatal Network, very preterm twins born between 240/7and 326/7weeks of gestation were included. Odds of morbidity and mortality of second-born cotwins compared with first-born cotwins were examined by matched-pair analysis. Outcomes were neonatal death, severe brain injury (intraventricular hemorrhage grade 3 or 4 or persistent periventricular echogenicity), bronchopulmonary dysplasia, severe retinopathy of prematurity (ROP) (> stage 2), necrotizing enterocolitis (≥ stage 2), and respiratory distress syndrome (RDS). Multivariable analysis was performed adjusting for confounders.ResultThere were 6,636 twins (3,318 pairs) included with a mean gestational age (GA) of 28.9 weeks. A higher rate of small for GA occurred in second-born twins (10 vs. 6%). Mortality was significantly lower for second-born twins (4.3 vs. 5.3%; adjusted odds ratio: 0.75; 95% confidence interval [CI]: 0.59-0.95). RDS (66 vs. 60%; adjusted odds ratio: 1.40; 95% CI: 1.29-1.52) and severe retinopathy (9 vs. 7%; adjusted odds ratio: 1.46; 95% CI: 1.07-2.01) were significantly higher in second-born twins.ConclusionThus, while second-born twins had reduced odds of mortality, they also had increased odds of RDS and ROP.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynaecology, Sunnybrook Health Sciences Centre, North York General Hospital, Toronto, Ontario, Canada.|Department of Obstetrics and Gynaecology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Elad
authors.initials: E
authors.lastname: Mei-Dan
authors.affiliation: Department of Paediatrics, Mount Sinai Hospital, Toronto, Ontario, Canada.|Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jyotsna
authors.initials: J
authors.lastname: Shah
authors.affiliation: Department of Paediatrics, Mount Sinai Hospital, Toronto, Ontario, Canada.|Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.|Department of Neonatology and Obstetrics and Gynaecology, Maternal-Infant Care (MiCare) Research Centre, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Shoo
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Paediatrics, Mount Sinai Hospital, Toronto, Ontario, Canada.|Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.|Department of Neonatology and Obstetrics and Gynaecology, Maternal-Infant Care (MiCare) Research Centre, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Prakesh S
authors.initials: PS
authors.lastname: Shah
authors.affiliation: Department of Obstetrics and Gynaecology, University of Toronto, Toronto, Ontario, Canada.|Department of Neonatology and Obstetrics and Gynaecology, Maternal-Infant Care (MiCare) Research Centre, Mount Sinai Hospital, Toronto, Ontario, Canada.|Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Kellie E
authors.initials: KE
authors.lastname: Murphy
mesh_terms: D001722:Birth Order; D002170:Canada / Q000453:epidemiology; D002423:Cause of Death; D016208:Databases, Factual; D020345:Enterocolitis, Necrotizing / Q000401:mortality*; D005260:Female; D005865:Gestational Age; D006801:Humans; D062071:Infant, Extremely Premature; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D066087:Perinatal Death / Q000209:etiology; D011247:Pregnancy; D059285:Pregnancy, Twin; D012127:Respiratory Distress Syndrome, Newborn / Q000401:mortality*; D012178:Retinopathy of Prematurity / Q000401:mortality*; D012189:Retrospective Studies; D014427:Twins