Length at birth and effect of prenatal and postnatal factors on early wheezing phenotypes. Kraków epidemiologic cohort study.

The main goal of the study was to assess the pattern of risk factors having an impact on the onset of early wheezing phenotypes in the birth cohort of 468 two-year-olds. A secondary objective was to investigate a possible association between early persistent wheezing and infant's length at birth. Approximately one third of the children in the study sample experienced wheezing in the first two years of life, and in about two third of cases (67%), the symptom developed within the first year of life. The early wheezing was easily reversible and in about 70% of the affected infants, the symptom receded in the second year of life. The adjusted relative risk ratio (RRR) of persistent wheezing increased with maternal atopy (RRR = 3.13; 95% CI: 1.35-7.27), house dampness (RRR = 3.94; 95% CI: 1.26-12.3), parity (RRR = 2.56; 95% CI: 1.51-4.32) and prenatal ETS exposure (RRR = 1.13; 95% CI: 1.05-1.22), but was inversely associated with the infant's length at birth (RRR = 0.87; 95% CI: 0.76-0.99). The data support the hypothesis that wheezing phenotypes in early childhood and possibly later in life may already be programmed in the prenatal and early postnatal period when the respiratory system is completing its growth and maturation.