CP prevalence by singletons and multiples and by categories of gestational age and birth weight
| Singletons | 95% CI | Multiples | 95% CI | RR | 95% CI | |
| Gestational age | ||||||
| <32 weeks | 47.35 | 44.50 to 50.34 | 45.84 | 41.43 to 50.60 | 0.97 | 0.86 to 1.08 |
| 32–36 weeks | 5.47 | 5.09 to 5.87 | 5.24 | 4.56 to 5.99 | 0.96 | 0.82 to 1.11 |
| Birth weight | ||||||
| 37+ weeks | 1.07 | 1.03 to 1.11 | 2.02 | 1.65 to 2.45 | 1.89 | 1.56 to 2.30 |
| <1500 g | 42.79 | 40.37 to 45.32 | 40.48 | 36.76 to 44.47 | 0.95 | 0.85 to 1.05 |
| 1500–2499 g | 8.37 | 7.92 to 8.83 | 6.58 | 5.90 to 7.31 | 0.79 | 0.70 to 0.88 |
| 2500+ g | 1.07 | 1.03 to 1.10 | 2.05 | 1.71 to 2.44 | 1.92 | 1.61 to 2.30 |
RRs represent the CP risk of multiples compared with singletons. Parameters in bold are significant at p<0.005
CP, cerebral palsy; RR, risk ratio.