Table 2A

Multilevel negative binomial regression coefficients of the total number of CP births on total live births by singletons and multiples

Model parametersSingletons95% CIMultiples95% CI
Intercept 0.002 0.001 to 0.003 0.010 0.001 to 0.013
Yearly rate of change0.9760.952 to 1.001 0.972 0.955 to 0.990
Overdispersion: Ln(Alpha)5.691 7.332 to4.049 3.008 4.039 to1.977
Between-centre variation
Initial status0.2390.092 to 0.6210.0420.006 to 0.288
Rate of change0.0020.001 to 0.004NA
Covariance −0.017−0.035 to 0.001NA
Model fit Wald χ2(1)=3.49, p=0.062 Wald χ2(1)=8.94, p=0.003.
  • Parameters in bold are significant at p<0.005. Comparisons of models using the likelihood ratio test indicated that estimating centre-level variance around the rate of change and the covariance between intercept and rate of change of Multiples did not improve model fit (at p<0.005). Therefore, these terms were not modelled.