Number of studies | Number of observations | Cohen’s d (95% CI, p value) | Difference between findings on domains of neurodevelopmental outcome | Heterogeneity, I^{2}
| Significant moderators | Egger’s intercept | |

Overall neurodevelopmental outcome | 47 | 2312 | −0.494 (−0.605 to −0.382, p<0.001) | 56.2% | Mean length of stay: b=−0.005, p<0.001, mean number of surgeries: b=−0.1371, p=0.003 | −1.874, p<0.001 | |

Cognitive outcome
| 39 | 2055 | −0.435 (−0.567 to −0.302, p=<0.001) | Q=3.194, p=0.343 | 63.7% | Mean number of surgeries: b=−0.0825, p=0.045 | −0.711, p=0.031 |

Motor outcome
| 33 | 1821 | −0.610 (−0.769 to −0.451, p=<0.001) | 70.3% | Mean length of stay: b=−0.005, p=0.008, mean number of surgeries: b=−0.1789, p=0.001 | −2.502, p<0.001 | |

Language outcome
| 14 | 701 | −0.670 (−0.914 to −0.425, p=<0.001) | 68.4% | – | −2.743, p=0.013 |