Table 5

Pooled OR (95% CI), heterogeneity (I2 and p value of the outcomes)

Cohort studies
OutcomeReference of studies includedTotal number of studies includedPooled OR (95% CI)I2 (%)P value
Mortality (unadjusted) 11–13 16 36 38 43 48 51 55 59 63 64 66 68 153.25 (2.10 to 5.03)70 <0.00001
Mortality (adjusted) 5 7 12 36 38 66 62.37 (1.40 to 4.01)36 0.001
Any-grade IVH (unadjusted) 7 11 13 16 46 48 51 55 60 68 102.30 (1.55 to 3.40)36 <0.00001
Any-grade IVH (adjusted) 7 38 22.60 (1.09 to 6.20)0 0.03
Severe IVH (unadjusted) 5 13 16 43 59 63 64 66 68 91.85 (1.37 to 2.51)39 <0.00001
Severe IVH (adjusted) 66 10.80 (0.20 to 3.20)NA0.75
Any-stage ROP (unadjusted) 13 38 40 48 55 59 68 71.78 (1.12 to 2.83)42 0.01
Any-stage ROP (adjusted) 38 40 23.70 (1.55 to 8.84)0 0.003
Severe ROP (unadjusted) 13 16 40 42 59 60 63 66 68 93.42 (1.82 to 6.41)64 0.0001
Severe ROP (adjusted) 8 66 68 31.97 (0.56 to 6.93)910.29
LOS (unadjusted) 11 13 16 36 43 48 59 63 64 91.97 (1.18 to 3.28)69 0.009
LOS (adjusted) 36 53 59 31.38 (0.41 to 4.72)810.60
Undefined NEC (unadjusted) 5 11 16 46 41.29 (0.72 to 2.30)00.39
Undefined NEC (adjusted)No study has reported
Severe NEC (unadjusted) 13 36 59 63 64 66 61.91 (0.74 to 4.89)470.18
Severe NEC (adjusted) 36 59 66 31.78 (0.29 to 10.7)650.53
CLD (unadjusted) 13 46 55 59 63 64 66 68 82.55 (1.96 to 3.30)0 <0.00001
CLD (adjusted) 38 59 66 31.42 (0.85 to 2.37)00.18
PVL (unadjusted) 13 63 64 66 41.01 (0.40 to 2.56)00.98
PVL (adjusted) 66 10.50 (0.20 to 1.25NA0.14
Any disability (unadjusted) 63 64 66 32.35 (1.47 to 3.73)0 0.003
Any disability (adjusted) 63 11.27 (0.56 to 2.86)NA0.57
Case–control studies
Mortality (unadjusted) 14 13.24 (0.72 to 14.44)NA0.12
Mortality (adjusted)No studies available
Any-grade IVH (unadjusted) 15 12.3 (1.3 to 4.07)NA 0.004
Any-grade IVH (adjusted)No studies available
Severe IVH (unadjusted) 14 15 22.58 (1.48 to 4.48)0 0.0008
Severe IVH (adjusted) 14 110.33 (10 to 10.67)NA <0.00001
Any-stage ROP (unadjusted) 37 44 69 36.49 (1.97 to 2139)82 0.002
Any-stage ROP (adjusted) 37 44 54 31.26 (0.79 to 2.00)520.33
Severe ROP (unadjusted) 45 50 65 32.15 (1.98 to 2.34)0 <0.00001
Severe ROP (adjusted) 45 50 54 61 41.01 (0.96 to 1.07)420.67
LOS (unadjusted)No studies available
LOS (adjusted)No studies available
Undefined NEC (unadjusted)No studies available
Undefined NEC (adjusted)No studies available
Severe NEC (unadjusted)No studies available
Severe NEC (adjusted)No studies available
CLD (unadjusted) 14 13.07 (0.87 to 10.81)NA0.08
CLD (adjusted)No studies available
PVL (unadjusted)No studies available
PVL (adjusted)No studies available
Any disability (unadjusted)No studies available
Any disability (adjusted)No studies available
  • CLD, chronic lung disease; IVH, intraventricular haemorrhage; LOS, late-onset sepsis; NA, not applicable; NEC, necrotising enterocolitis; PVL, periventricular leucomalacia; ROP, retinopathy of prematurity.