Pregnant woman exposed to pollen make baby prone to asthma

A study of more than 110,000 pregnant women found that high pollen count was associated with a 35 per cent increased risk of infants being taken to hospital because of asthma, the Daily Mail reported.

But among children of heavy-smoking mothers the exposure to high pollen levels during the first three months of life appeared to reduce the risk of asthma.

Yet infants exposed in the first three months of life had a reduced risk.

Researchers took account of a range of factors that could have swayed the results, including mothers' smoking habits, infant gender, stage of pregnancy at birth, and season of birth.

The findings are reported today in the journal Allergy, Asthma and Clinical Immunology.

Women with allergies may have reactions to pollen that affect the unborn baby's environment and affect immune system development, the researchers said.

It is also possible that pregnant women with severe reactions to pollen suffer complications that affect the child, it is claimed.

"It is likely that pollen sensitised mothers exposed to high levels of pollen during pregnancy are at increased risk of symptoms and asthma exacerbations. This may in turn change the intrauterine environment.." the researchers, led by Adrian Lowe, from the University of Umea said.

"Alternatively, symptomatic mothers during high pollen periods may have an increased risk of pregnancy complications, including pre-eclampsia, pre-term birth and impaired foetal growth, which could influence the risk of wheezing illness."

"Further work is required to elucidate exactly how pollen exposure may prime the foetal immune system towards severe respiratory illness in early life."

Pollen comes from grass, trees and flowers. Counts can vary markedly season to season and year to year but are highest from late spring to early autumn.

For each child, pollen count was assessed during the first and last 12 weeks of pregnancy, as well as the first 12 weeks of life.