Table 3

Study characteristics and outcomes for studies characterising neonates by gestational age and birth weight

Categorisation methodType of study (comparator groups)StudyCountry of studyTotal number of babiesPopulation (gestation (weeks +days)/birth weight (g))Outcomes reported by included studies
Mortality timeframeSurvival timeframeMorbidity
UndefinedPerinatalNeonatalDischargeInfant2 yearsDischarge2 years
Gestational ageInutero versus exutero transfer to NICULamont et al28UK20628+0–29+6Embedded ImageNon-significant difference in incidence of IVH.
30+0–31+6NSSignificant reduction in incidence of IVH.
Truffert et al31France15727+0–30+6NSNon-significant difference in incidence of survival (up to 2 years of age) without disability.*
Hauspy et al32Belgium31528+0–29+6NSNon-significant difference in incidence of RDS.
Lee et al33Canada214827+0–29+6NSNon-significant difference in incidence of IVH, NEC and ROP.
Significant reduction in incidence of RDS and CLD.
30+0–31+6NSNon-significant difference in incidence of IVH, NEC, ROP and CLD.
Significant reduction in incidence of RDS.
Boland et al13Australia25028+0–31+6
Embedded Image
No other outcomes measured.
Level of unit of birth (NICU vs non-NICU)Holmgren and Högberg 34Sweden39428+0–31+6NSNSNSNon-significant difference in incidence of asphyxia†
Johansson et al29Sweden163628+0–31+6NSNo other outcomes measured.
Level of unit of care (NICU vs non-NICU)Field et al30UK17129+0–30+6NSNo other outcomes measured.
Jonas and Lumley35Australia333128+0–31+6Embedded ImageNo other outcomes measured.
Birth weightInutero versus exutero transfer to NICUMiller et al38USA941000–1500Embedded ImageNo other outcomes measured.
Watkinson and McIntosh44UK1541001–1500Embedded ImageNo other outcomes measured.
Powell and Pharoah42UK3901000–1500Embedded ImageNo other outcomes measured.
Obladen et al40Germany2201000–1249NSNon-significant difference in incidence of IVH.
1250–1499NSNo other outcomes measured.
Mohamed and Aly39USA36 4931000–1500Significant reduction in incidence of IVH.
Level of unit of birth (NICU vs non-NICU)Gortmaker et al36USA48741000–1500Embedded ImageEmbedded ImageNo other outcomes measured.
Powell et al41USA9471000–1500NSNo other outcomes measured.
Yeast et al1USA28521000–1500Embedded ImageNo other outcomes measured.
Sanderson et al43USA13451000–1249Embedded ImageNo other outcomes measured.
1250–1499NSNo other outcomes measured.
Gould et al37USAundefined (<4405)1000–1500NSNo other outcomes measured.
Warner et al18USA4741000–1500NSNon-significant difference in incidence of NEC (Bell stage II or III) or death.
Significant reduction in incidence of BPD or death, IVH (grade III or IV) or death, ROP or death.
  • ↑denotes direction of significant difference found between comparator groups (first comparator vs second comparator), and NS denotes lack of significant difference between comparator groups). For example, Jonas 1997 showed a significantly lower (arrow in downward direction) neonatal mortality for those babies born between 28+0 and 31+6 in a NICU (first comparator) versus a non-NICU (second comparator).

  • *Disability is a composite outcome measure consisting of cerebral palsy, deafness, Brunet-Lézine developmental score <80.63

  • †Asphyxia refers to Apgar score <5 at 10 min of age.

  • BPD, bronchopulmonary dysplasia; CLD, chronic lung disease; IVH, intraventricular haemorrhage; NEC, necrotising enterocolitis; NICU, neonatal intensive care unit; RDS, respiratory distress syndrome; ROP, retinopathy of prematurity.