Conclusions
We provide evidence that is consistent with the hypothesis that maternal
exposure to greenness during pregnancy increases the risk of developing
asthma in childhood. Our results indicate that this is strongest when
the exposure occurs in the spring season and in the third trimester of
pregnancy. The mechanisms underlying these adverse effects are not fully
understood, but they are likely to be related to high allergen
concentrations, especially pollen from high vegetation biomass.
Moreover, it is important to note that the timing of exposure during
pregnancy may play a critical role in the effects of greenness on risk
of developing asthma in childhood and later in life.