The World Health Organisation estimates that one in four couples globally require assistance to conceive. Biologically, Assisted Reproductive Technologies (ART) are associated with greater risk of adverse pregnancy outcomes and long-term consequences for the mother and child. However, the link between asthma and its increased rate in ART offspring remains unclear.
A study, published online in the journal Thorax, found that children whose parents take more than a year to get pregnant or use fertility treatment may be at heightened risk of developing asthma.
The Study
As reported in ScienceDaily, the researchers linked birth and prescription data from national Norwegian health registries (involving 474,402 children born between 1998 and 2009) and from the Norwegian Mother and Child Cohort Study (75,797 children).
To define childhood asthma, the criterion was the use of asthma drugs in the 12 months preceding the child completing seven years.
They collected information on fertility treatment, time taken before conceiving, history of miscarriages, and other factors like maternal age, asthma, smoking during pregnancy and weight before pregnancy.
A little over four percent of children in the registries group (20,189) and mother and child study (3229) had asthma.
Children in both the groups who had been conceived with the aid of fertility treatment were up to 42 per cent more likely to have asthma.
When compared with those children whose parents had spontaneously conceived after more than 12 months, they were 22 per cent more likely to have asthma.
The findings suggested that poorer fertility cannot explain the observed heightened asthma risk among children conceived with the aid of fertility treatment. Certain aspects of ART may play a role.
The number of previous miscarriages also led to a heightened risk of asthma, rising from 7 per cent for one, to 24 per cent for three or more, although this was only observed for miscarriage during the first 12 weeks of pregnancy.
To explain these observations, it can be noted that many procedures involved in fertility treatments can affect the embryo and the natural course of fetal development.
ScienceDaily quotes the researchers as saying,
We propose that common immunological mechanisms might plausibly underlie the increased risk of asthma we observed both among children of mothers who suffer from subfertility and miscarriages, since immunological mechanisms contribute both to problems conceiving and repeat pregnancy losses.
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