Table 2 Odds ratios (95% CI) for mortality and major morbidities by z score for birth weight (BW) and estimated fetal weight (EFW).
| Z score | < −3.00 | −2.99 to −2.00 | −1.99 to −1.00 | −0.99 to 0.99 | 1.00 to 1.99 | 2.00 to 2.99 | >3.00 | χ2 trend | |
|---|---|---|---|---|---|---|---|---|---|
| No of cases in each Z score category | BW | 114 | 422 | 1174 | 4843 | 1008 | 250 | 87 | |
| EFW | 565 | 950 | 1870 | 3779 | 512 | 153 | 69 | ||
| Mortality | BW | 2.14 (1.40 to 3.28)*** | 1.19 (0.90 to 1.58) | 1.07 0.88 to 1.29) | 1.00 | 0.70 (0.55 to 0.88)** | 0.50 (0.31 to 0.83)** | 0.86 (0.45 to 1.68) | 15.7, p<0.001 |
| EFW | 1.63 (1.30 to 2.04)*** | 0.96 (0.77 to 1.18) | 0.94 (0.80 to 1.11) | 1.00 | 1.37 (1.07 to 1.74)** | 1.07 (0.67 to 1.69) | 2.23 (1.29 to 3.84)** | 0.5, p = 0.8 | |
| Periventricular haemorrhage (all) | BW | 0.54 (0.36 to 0.81)** | 0.58 ( 0.47 to 0.73)*** | 0.78 (0.68 to 0.90)*** | 1.00 | 1.02 (0.88 to 1.17) | 0.93 (0.72 to 1.21) | 1.08 (0.71 to 1.66) | 31.0, p<0.001 |
| EFW | 0.54 (0.44 to 0.65)*** | 0.63 (0.54 to 0.73)*** | 0.79 (0.71 to 0.89)*** | 1.00 | 1.12 (0.93 to 1.35) | 0.92 (0.66 to 1.27) | 0.99 (0.62 to 1.61) | 68.5, p<0.001 | |
| Septicaemia | BW | 1.18 (0.78 to 1.79) | 1.06 (0.84 to 1.33) | 1.07 (0.93 to 1.24) | 1.00 | 0.81 (0.69 to 0.96)* | 0.83 (0.61 to 1.13) | 0.55 (0.31 to 1.00)* | 10.8, p = 0.001 |
| EFW | 1.29 (1.06 to 1.58)** | 1.07 (0.91 to 1.27) | 1.07 (0.94 to 1.22) | 1.00 | 0.98 (0.79 to 1.22) | 1.25 (0.86 to 1.80) | 0.78 (0.43 to 1.44) | 4.8, p = 0.03 | |
| Chronic lung disease | BW | 1.10 (0.66 to 1.83) | 1.05 (0.79 to 1.40) | 0.98 (0.82 to 1.19) | 1.00 | 0.66 (0.53 to 0.83)*** | 0.62 (0.40 to 0.97)* | 0.38 (0.15 to 0.93)* | 19.5, p<0.001 |
| EFW | 1.45 (1.14 to 1.84)** | 1.10 (0.89 to 1.36) | 1.08 (0.89 to 1.27) | 1.00 | 1.24 (0.96 to 1.61) | 1.34 (0.85 to 2.10) | 0.81 (0.37 to 1.78) | 2.6, p = 0.1 | |
| Persistent ductus arteriosus | BW | 0.94 (0.54 to 1.66) | 0.79 (0.56 to 1.10) | 0.82 (0.66 to 1.01) | 1.00 | 0.68 (0.54 to 0.86)** | 0.47 (0.28 to 0.80)** | 0.26 (0.08 to 0.81)* | 2.5, p = 0.1 |
| EFW | 0.97 (0.74 to 1.29) | 0.94 (0.75 to 1.18) | 0.86 (0.72 to 1.03) | 1.00 | 1.04 (0.78 to 1.38) | 1.02 (0.62 to 1.68) | 0.59 (0.24 to 1.48) | 0.2, p = 0.7 | |
| Necrotising enterocolitis | BW | 3.44 (1.97 to 6.02)*** | 1.87 (1.26 to 2.79)** | 0.91 (0.64 to 1.27) | 1.00 | 0.71 (0.48 to 1.06) | 0.50 (0.21 to 1.24) | 0.28 (0.04 to 2.03) | 31.5, p<0.001 |
| EFW | 2.48 (1.77 to 3.47)*** | 1.01 (0.69 to 1.47) | 1.03 (0.77 to 1.38) | 1.00 | 1.05 (0.65 to 1.70) | 0.71 (0.26 to 1.95) | 1.22 (0.38 to 3.91) | 12.5, p<0.001 |
*p<0.05, ** p<0.01, *** p<0.001.