Table 3

Risk of asthma in the lower birthweight twin relative to the higher birthweight twin in a sample of Danish twin pairs, 3–9 years of age

Birth weight difference (g)All twin pairsMZ twin pairsDZ twin pairsORMZ=ORDZ
OR (95% CI)p ValueOR (95% CI)p ValueOR (95% CI)p Valuep Value*
Any difference†1.31 (1.03 to 1.65)0.0271.33 (0.72 to 2.46)0.3561.29 (1.08 to 1.54)0.0050.935
≥1001.26 (1.05 to 1.57)0.0151.75 (0.86 to 3.56)0.1221.23 (1.01 to 1.49)0.0420.516
≥2001.29 (1.04 to 1.60)0.0191.71 (0.68 to 4.35)0.2571.28 (1.02 to 1.61)0.0300.661
≥3001.40 (1.09 to 1.81)0.0083.33 (0.92 to 12.11)0.0671.37 (1.05 to 1.77)0.0190.413
≥4001.21 (0.91 to 1.81)0.1922.33 (0.60 to 9.02)0.2201.21 (0.90 to 1.63)0.2020.524
≥5001.20 (0.84 to 1.71)0.3222.50 (0.49 to 12.89)0.2731.17 (0.81 to 1.69)0.4020.538
  • * Test for heterogeneity between OR for MZ and DZ twin pairs.

  • Adjusted for sex, birth length and Apgar score.

  • MZ, monozygotic; DZ, dizygotic.