| Profit et al. | USA | Delphi | Antenatal steroids, timely retinopathy of prematurity exam, late onset sepsis, hypothermia on admission, pneumothorax, growth velocity, oxygen at 36 weeks postmenstrual age, any human milk feeding at discharge, in-hospital mortality | 2011 | (7) |
| Kaplan et al. | USA | HIS data analysis | Surfactant use rate for premature babies | 2011 | (8) |
| Neogi et al. | India | Cross sectional survey | Nurse: bed ratio, Doctor: bed ratio, Reported time (months) for repair of essential equipment, Asepsis score, Average duration (days) of stay, Bed Occupancy rate | 2011 | (9) |
| Nowakowski et al. | USA | Cross sectional survey | Regulation of regionalization programs, data surveillance, review of adverse events | 2012 | (10) |
| Toome et al. | Estonia | Population based reports | Proportion of infants born by cesarean, received antenatal corticosteroids, maternal antibiotics, and surfactant | 2012 | (11) |
| Neogi et al. | India | Review | Regionalization of perinatal care, staff: bed ratio, existence of residential medical staff, NMR | 2012 | (12) |
| Gale et al. | UK | Population-wide observation | Volume of neonatal specialist care (≥ 2000 neonatal intensive care days annually), having an acute transfer (within the first 24 hours after birth) and/or a late transfer (between 24 hours and 28 days after birth) to another hospital, assessed by change in distribution of transfer category (“none,” “acute,” “late”), and babies from multiple births separated by transfer | 2012 | (13) |
| Oestergaard et al. | Switzerland | Neonatal mortality data base 0f 38 countries | NMR trends | 2011 | (14) |
| Tamburlini et al. | Italy | Survey | Existence of basic amenities, existence of essential drugs and equipment, hygienic practice, existence of surveillance system | 2011 | (15) |
| Marston et al. | UK | Review | skilled care before/during/after birth and maternal/newborn mortality/morbidity | 2013 | (16) |
| Tamburlini et al. | Italy | Before-after observational study | No. of nurses, doctors, drugs, equipment: bed, normal delivery/ section proportion, thermal control, use of Apgar score, promotion of breastfeeding, neonatal resuscitation, mothers more involved in neonatal care, training more staff in effective perinatal care | 2013 | (17) |
| Phibbs et al. | USA | Record linkage | The percentage of very-low-birth-weight deliveries in level 3 hospitals, mortality: volume of NICU | 2007 | (18) |
| Rogowski et al. | UK | Retrospective observational | Mortality of VLBW before discharge to home in each hospital level | 2004 | (19) |
| Saugstad | Norway | Review | Regionalization implementation, promotion of breast feeding, investing in equipment and staff, evidence-based treatment, training programs | 2011 | (20) |
| Lindmark and Langhoff-Roos | Sweden | Retrospective observational | Fetal mortality rate, neonatal mortality rate, infant mortality rate. Distribution of birth weight, distribution of gestational age, prevalence of congenital anomalies, distribution of Apgar score at 5 min | 2004 | (21) |
| Marcin | USA | Retrospective observational | NICU mortality rate, standardized mortality ratio, standardized NICU length of stay ratio | 2000 | (22) |
| Heidarzade | IR Iran | FGD | Advanced resuscitation certificated staff attendance rate during resuscitation, pediatrician/pediatric resident attendance rate during resuscitation, neonatologist/neonatology fellow attendance rate during resuscitation, existence of residential pediatrician/neonatologist, FHR monitoring during labor, partograph filling for vaginal deliveries, parent’s training before discharge, resuscitation form filling for performed ones, fetomaternal transfer rate, neonatal transform organized by transfer guide, hypoxia on admission, mean/median duration of NICU stay, mean/ median duration of mechanical ventilation in NICU, proportion of newborns who receipt required follow up, perinatal mortality rate, primary c/s rate, repeat c/s rate, mother readmission rate | 2010 | (23) |
| Pollack and Koch | USA | Multiple center cohort | Bronchopulmonary dysplasia (BPD), periventricular/intraventricular hemorrhage or periventricular leukomalacia (PIVH/PVL), and retinopathy of prematurity (ROP). duration of hospital stay and days on a ventilator for those infants who received mechanical ventilation, organizational measures: quality of teamwork and leadership, degree of relationships and communications within the NICU, degree of coordination, perceived unit/team effectiveness, authority, quality of conflict resolution, job satisfaction | 2003 | (24) |