PI Group, N = 72 | PC Group, N = 74 | TR Group, N = 75 | |
---|---|---|---|

Infant characteristics | |||

BW, mean ± SD, g | 1396 ± 429 | 1381 ± 436 | 3619 ± 490 |

400–1000 g, n (%) | 20 (28) | 20 (27) | |

1001–1500 g, n (%) | 15 (21) | 20 (27) | |

1501–2000 g, n (%) | 37 (51) | 34 (46) | |

GA, mean ± SD, wk | 30.2 ± 3.1 | 29.9 ± 3.5 | 39.3 ± 1.3 |

<28 wk, n (%) | 17 (24) | 19 (27) | |

28–32 wk, n (%) | 36 (50) | 37 (50) | |

≥ 33 wk, n (%) | 19 (26) | 18 (24) | |

Boy, n (%) | 38 (53) | 39 (53) | 40 (54) |

Twin, n (%) | 16 (22) | 14 (19) | 0 |

Prenatal steroid use, n (%) | 53 (74) | 57 (77) | |

SNAP II, mean ± SD | 8.3 ± 10.9 | 10.4 ± 11.3 | |

CRIB score, mean ± SD, N = 85 | 3.2 ± 2.8 | 2.7 ± 2.9 | |

Received ventilation, n (%) | 29 (40) | 37 (50) | |

Duration of ventilation, mean ± SD, d, N = 62 | 7.0 ± 18.6 | 7.1 ± 17.3 | |

Postnatal steroid use, n (%) | 9 (13) | 10 (14) | |

Oxygen therapy at 36 wk of gestation, n (%) | 11 (15) | 14 (19) | |

Abnormal cerebral ultrasound, n (%) | |||

IVH grade 1 or 2 | 7 (10) | 8 (11) | |

IVH grade 3 or 4 | 3 (4) | 5 (7) | |

Periventricular leukomalacia | 4 (6) | 8 (11) | |

Maternal and social characteristics | |||

Mother’s age, mean ± SD, y | 30.8 ± 6.1 | 29.1 ± 6.4 | 29.7 ± 6.1 |

Firstborn child, n (%) | 40 (56) | 37 (54) | 27 (37) |

Mother’s education, mean ± SD, y, N = 131^{a}^{,}^{b} | 14.6 ± 2.8 | 13.5 ± 3.2 | 14.9 ± 2.8 |

Father’s education, mean ± SD, y, N = 131^{a} | 13.8 ± 3.1 | 13.5 ± 3.2 | 14.4 ± 3.2 |

Mother’s monthly income, mean ± SD, 1000 Norwegian kroner, N = 131^{a} | 15.8 ± 7.7 | 14.6 ± 6.7 | 15.9 ± 8.0 |

Father’s monthly income, mean ± SD, 1000 Norwegian kroner, N = 131^{a} | 21.1 ± 8.7 | 19.9 ± 8.1 | 21.9 ± 9.8 |

CRIB, Clinical Risk Index for Babies (includes BW, GA, congenital malformations, maximum base deficit in the first 12 hours, minimal appropriate fraction of inspired oxygen in the first 12 hours, and maximal appropriate fraction of inspired oxygen in the first 12 hours); IVH, intraventricular hemorrhage; SNAP II, Score of Neonatal Acute Physiology II (includes mean blood pressure, lowest temperature, P

_{O2}/fraction of inspired oxygen ratio, serum pH, multiple seizures, and urine output).↵a Calculated for 131 families due to 15 twin pairs.

↵b Mean difference: 1.1 years (95% CI: 0.03 – 2.2 years);

*P*= .04.