Overall apparent model performance and by cohort: UK (Allen et al, 2017),32 Australia (Rumbold et al, 2006),31 Norway (STORK Groruddalen research programme, 2010),33 and US (National Institute of Child Health and Human Development (NICHD), 2018)34 cohorts, and pooled data
| Pooled estimate | Allen et al, 2017 (n=1045) | Rumbold et al, 2006 (n=1877) | STORK Groruddalen, 2010 (n=823) | NICHD, 2018 (n=233 483) | Pooled data (n=237 228) | |
| Calibration slope | ||||||
| Point estimate | 0.99 | 0.88 | 1.04 | 1.03 | 0.99 | 0.99 |
| Confidence interval | 0.88 to 1.10 | 0.89 to 0.96 | 0.99 to 1.09 | 0.95 to 1.11 | 0.99 to 0.99 | 0.99 to 0.99 |
| Prediction interval | 0.70 to 1.28 | — | — | — | — | — |
| τ2 (95% CI) | 0.00 (0.00 to 0.04) | — | — | — | — | — |
| Calibration-in-the-large (g) | ||||||
| Point estimate | 44.45 | 33.11 | 13.40 | 104.69 | 31.43 | 31.53 |
| Confidence interval | −18.44 to 107.33 | 7.07 to 59.14 | −6.45 to 33.26 | 75.62 to 133.76 | 29.69 to 33.17 | 29.81 to 33.26 |
| Prediction interval | −136.62 to 225.51 | — | — | — | — | — |
| τ2 (95% CI) | 1400 (257 to 13000) | — | — | — | — | — |
| Observed to expected birth weight ratio | ||||||
| Point estimate | 1.02 | 1.01 | 1.01 | 1.04 | 1.01 | 1.01 |
| Confidence interval | 0.97 to 1.07 | 0.96 to 1.06 | 0.94 to 1.07 | 0.98 to 1.09 | 0.92 to 1.11 | 0.92 to 1.11 |
| Prediction interval | 0.95 to 1.08 | — | — | — | — | — |
| τ2 (95% CI) | 0.00 (0.00 to 0.00) | — | — | — | — | — |
| R2* (%) | ||||||
| Median | 46.9 | 32.7 | 47.8 | 45.7 | 56.1 | 56.0 |
| Range | 32.3-56.3 | 32.3-32.9 | 47.5-48.1 | 45.1-46.3 | 56.0-56.3 | 55.9-56.1 |
| Interquartile range | 39.0-52.1 | 32.6-32.8 | 47.8-47.9 | 45.6-45.9 | 56.1-56.2 | 56.0-56.1 |
*Reported as median, range, and interquartile range for imputations because R2 cannot be summarised for all imputations with Rubin's rules.
CI, confidence interval.