Variable | Twin Pairs | One or Both Affected | Rate, % | Expected Concordance | Observed Concordance | P |
---|---|---|---|---|---|---|

IVH | ||||||

Monozygotic | 61^{a} | 16 | 22.36^{b} | 3.05^{c} | 1 | .113 |

Dizygotic | 185^{a} | 39 | 9.25^{c} | 6 | ||

NEC | ||||||

Monozygotic | 63 | 9 | 15.08^{d} | 1.43^{e} | 1 | .022 |

Dizygotic | 189 | 29 | 4.30^{e} | 9 | ||

BPD | ||||||

Monozygotic | 63 | 18 | 24.21^{f} | 3.69^{g} | 12 | <.0001 |

Dizygotic | 189 | 43 | 11.07^{g} | 15 |

↵a IVH missing data.

↵b NEC: Rate was calculated as (16 + 39)/246, expressed as a percentage.

↵c Expected concordance was calculated as 61 (0.224)

^{2}for monozygotic and 185 (0.224)^{2}for dizygotic.↵d NEC: rate was calculated as (9 + 29)/252, expressed as a percentage.

↵e Expected concordance was calculated as 63 (0.151)

^{2}for monozygotic and 189 (0.151)^{2}for dizygotic.↵f BPD: rate was calculated as (18 + 43)/252, expressed as a percentage.

↵g Expected concordance was calculated as 63 (0.242)

^{2}for monozygotic and 189 (0.242)^{2}for dizygotic.