Table 5

Comparison of individual birth factors within asthma discordant twin pairs by zygosity. Median differences with non-parametric 95% confidence intervals (CI)^5-1

Perinatal factors		MZ intrapair difference			DZ intrapair difference
Perinatal factors		Median (no. of pairs)^5-2	95% CI		p value^5-3	Median (no. of pairs)^5-2	95% CI	p value^5-3
Birth weight (g)	−135 (32)	−240 to +100	0.26	+50 (101)	−40 to +150	0.22
Ponderal index (kg/m^5-3)	−0.14 (32)	−1.22 to +0.91	0.84	+0.59 (100)	−0.14 to +1.12	0.03
Apgar score	0 (25)	0	0.60	0 (82)	0	0.49

↵5-1 The differences between MZ and DZ with Wilcoxon rank sum test were not significant.
↵5-2 Median of the intrapair differences (affected minus unaffected).
↵5-3 Wilcoxon signed rank test.