Objectives: Pollen exposure is an environmental risk factor for asthma symptoms and allergic reactions in children. However, the extent to which pollen exposure in pregnancy and early life influences the development of childhood asthma is not fully understood. We aimed to assess the associations between pollen exposure during pregnancy and early pollen exposure in the first year of life with childhood asthma at age 6 years.

Methods: We assessed prenatal pollen exposure as the sum of pollen counts during 40 weeks of pregnancy and postnatal exposure as the sum of pollen counts from birth date to start of pollen season. Standardized questionnaires were used to collect data on patient demographics, asthma diagnosis, and related risk factors.

Results: Increased pollen exposure during pregnancy and infancy were associated with increased odds of childhood asthma at age 6 (OR = 1.14, 95% CI 1.05-1.24, p = 0.002; OR = 1.18 95% CI 1.08-1.29, p = 0.0003, respectively).

Conclusions: We conclude that higher early life (both pre- and postnatal) exposure is strongly associated with asthma development. Further studies are needed to validate these findings and to elucidate the mechanisms of early life exposures to pollen on childhood asthma etiology. Future findings could have implications for therapeutic regimens targeted at environmental triggers of asthma.