A new study from the UK finds that asthma is more common in children born after in vitro fertilization or IVF. But the researchers say parents of children born after assisted reproduction technology (ART) should not be worried about this because in terms of absolute risk, there is not a lot of difference.

The researchers, from the universities of Oxford and Essex, write about their study, which uses data from the UK Millennium Cohort Study, in the 5 December online issue of the journal Human Reproduction.

They find that among children aged 5 years, those conceived via ART, or who were born to parents who had to wait more than a year before managing to conceive, were more likely to have asthma, experience wheezing, and be on anti-asthmatic drugs.

Their analysis showed the link was driven mainly by children following IVF or intracytoplasmic sperm injection (ICSI). They were between two and four times more likely to have asthma, wheezing or be taking anti-asthmatic medication.

Lead author Claire Carson is a researcher at Oxford University’s National Perinatal Epidemiology Unit. She says in a press statement:

“15% of the children in our study had asthma at the age of five. Although this figure was higher, 24%, in the IVF children, it isn’t much higher than the one in five risk for all children in the UK.”

She also notes that although they found this link between IVF and asthma, they haven’t been able to establish that IVF actually causes asthma.

Further research is needed to determine that, she adds, and points out:

“It is also important to remember that for most children, asthma is a manageable condition and shouldn’t prevent children from living a full and active life.”

The UK Millennium Cohort Study is one of the few large observational studies that has data about conception methods, asthma, and potential influencing factors like social circumstances and lifestyle.

The Study is following neary 19,000 children all over the UK who were born between 2000 and 2002.

For this latest piece of research, the Oxford and Essex team used data on single birth children (no twins) at age 5 and 7. Among the 5-year-olds, just over 100 were born after ART.

The data includes information from surveys with parents, and shows whether the children had ever been diagnosed with asthma, experienced wheezing, or were taking drugs for asthma.

The researchers were also able to include other data on factors that might influence the development of asthma, such as premature birth, the mothers’ history of asthma, whether they smoked, their body mass index, socioeconomic status, and even if there were furry pets at home.

Carson and colleagues suggest there could be several reasons for the link between ART and asthma, such as the severity of the infertility, the type of treatment, and even perhaps that over-protective ART parents are more likely to report asthma symptoms, although they believe this is unlikely.

There could also be other explanations from factors they have no information on.

They urge people to be cautious with these findings because although it appears that the ART group is the one particularly at high risk for developing asthma, the study only had a relatively small number of IVF cases.

The team is continuing to follow the children to see if the same effect is present when they are 11 years old.

They suggest more studies should now be done with larger groups of children born after ART to confirm the findings.

The world’s first test tube baby, Louise Brown, was born in the UK in July 1978.

Since then, over 5 million babies have been born following ART.

Written by Catharine Paddock PhD