A recent study by Swedish researchers has found that babies in the womb have a greater risk of contracting asthma due to high pollen exposure in the last trimester of pregnancy.
Few earlier studies have directly measured pollen exposure at different points during pregnancy and in the early life of the infant, assessing their effects on the risk of respiratory disease outcome. In this study involving more than 110,000 pregnant women, it was found that high pollen count in these women was linked to an increase in risk of the infant born needing hospitalization due to asthma by almost 35 percent.
For the study, pollen exposure of pregnant women during the first and last 12 weeks of pregnancy and first 12 weeks of infancy of children conceived by women residing in Stockholm, Sweden between 1988 and 1995 was calculated. The hospital admission record of infants in their first year for respiratory conditions was also collected.
Out of the 110,381 children observed, 940 were hospitalized for asthma in their first year. Pollen levels showed significant seasonal variations and between year differences. Exposure to high pollen during the first 12 weeks of pregnancy was linked to increase in risk of hospitalization due to asthma. Exposure to high pollen during first 12 weeks of pregnancy showed reduced risk but only in case of infants born to heavy-smoking mothers.
While making these conclusions, researchers discounted other factors which could affect the results including smoking habits of the expectant mothers, gender of the infant, and stage of the pregnancy at the time of birth of the infant; and season in which the infant was born. Researchers led by Adrain Lowe from University of Umea said that women already suffering from allergies may have reactions when exposed to pollen which can affect the unborn infant's environment and adversely affect its immune system development.
They also suggested that pregnant women with severe allergy to pollen may develop severe reactions; pregnancy complications like pre-eclampsia, premature birth or impaired foetal growth which could also influence risk of wheezing illness. They could also suffer other complications which can affect the infant.