Table 2A

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

 Model parameters Singletons 95% CI Multiples 95% CI Intercept 0.002 0.001 to 0.003 0.010 0.001 to 0.013 Yearly rate of change 0.976 0.952 to 1.001 0.972 0.955 to 0.990 Overdispersion: Ln(Alpha) −5.691 −7.332 to −4.049 −3.008 −4.039 to −1.977 Between-centre variation Initial status 0.239 0.092 to 0.621 0.042 0.006 to 0.288 Rate of change 0.002 0.001 to 0.004 NA Covariance −0.017 −0.035 to 0.001 NA 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.