Better Outcomes Registry and Network(BORN)Ontario Children's Hospital of Eastern Ontario Research Institute 401 Smyth Road Ottawa ON Canada K1H 8LI;
Perinatal Epidemiology Research Unit Departments of Obstetrics and Gynaecology and Pediatrics Dalhousie University Halifax NS Canada B3K 6R8;
Canadian Centre for Vaccinology Dalhousie University Halifax NS Canada B3K 6R8;
Canadian Centre for Vaccinology Dalhousie University Halifax NS Canada B3K 6R8;
中华妇产科杂志编辑部;
