Based on descriptive statistics analysis, the prevalence of “wheeze ever” and “wheeze in the past 12 months” in age group 6-7 years and in both genders in this group was higher than age group 13-14 years. Also, in children with birth weight under 1.5 kg (and in both genders in this group), the prevalence of “wheeze after exercise in the past 12 months” and “night cough in the past 12 months” was higher than other birth weight groups. The prevalence of studied symptoms with respect to birth weight and gender is shown in Table 2