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British discovery:
Anxious pregnant women
are more likely to have asthmatic children
Pregnant women who are stressed, particularly late in
pregnancy, have an increased risk of their child going on to
develop asthma. So finds a British study conducted on a cohort
of over 5,800 families and presented in Berlin at the Annual
Congress of the European Respiratory Society (ERS). Very
anxious pregnant women are 65% more likely to have a child
who later develops asthma than mothers with a lower level of
anxiety.
Asthma, the commonest chronic paediatric condition, affects approximately one child in ten.
Although the causes of this respiratory condition are not yet entirely clear, it is known that
attacks can be provoked inter alia by psychological or emotional factors.
Two studies have recently demonstrated a connection between anxiety in those close to the
child (such as the mother, or, in some cases, the child’s social worker) and early onset of
wheezing. But both of those studies only examined the post-natal period.
Yet experiments with adult mammals exposed to in-utero stress have shown that the subjects
demonstrated changes both in the hypothalamo-hypophysary axis (which controls the
hormones connected with major functions of the body) and in the immune system. These
shifts made them more vulnerable to inflammation of the airways and bronchial
hyperreactivity.
Over 5,800 families monitored for eight years
Noting that no comparable data existed for humans, Raquel Granell (Department of Social
Medicine, University of Bristol, UK) and her team decided to conduct a major prospective
study on the subject.
“Our first hypothesis was that maternal stress in pregnancy was associated with paediatric
asthma. The second was that this effect was not mediated by an allergic mechanism and
would be stronger in non-atopic children than in their atopic counterparts”, Granell explained
in Berlin.
The results presented to the Congress provide a striking confirmation of the first of the British
team’s hypotheses.
In order to analyse the effect of antenatal psychological factors on asthma, the Bristol
researchers studied subjects from ALSPAC (Avon Longitudinal Study of Parents and
Children), a cohort of pregnant women living in the former county of Avon, who were due to
give birth between 1 April 1991 and 31 December 1992.
ALSPAC, which has already led to a number of publications on various issues, sought
primarily to identify the role of genetic and environmental factors on child development. It
covered a total of more than 14,000 families.
Granell analysed data from 5,810 mothers with children for whom the data needed for her
study were available.
Maternal anxiety was assessed by self-completion questionnaires that the mothers filled in at
18 and 32 weeks of pregnancy. On the basis of the responses, the researchers were able to
divide the women into four groups with different levels of anxiety. Their children were
assessed for asthma at the age of approximately 7.5 years, likewise by means of
questionnaires completed by the mothers.
At the clinical level, bronchial hyperreactivity was also tested for when the children reached
age eight, and skin prick tests were used to see whether a subject’s asthma was of allergic
origin and to which allergens the child reacted.
Almost 13% of the children were found to have asthma. As expected, the authors confirmed a
strong connection between maternal anxiety at 18 and, particularly, 32 weeks of pregnancy,
and asthma in children aged 7.5 years.
The asthma risk was found to be 17% higher for children born to mothers who were stressed
at 32 weeks, and 14% higher where the mother was stressed at 18 weeks, Granell told the
Congress.
Severe anxiety multiplies the asthma risk by 1.65
The results were even more striking for women belonging to the most anxious group: the
additional risk of asthma in the child could reach 65% for those in the highest-stress group at
32 weeks and 53% for those severely stressed at 18 weeks.
These relative increases in the risk of asthma are slightly mitigated when all other relevant
factors are eliminated, but, as the authors emphasised, they remain significant.
Granell and her team also pointed out that they had not identified any bias arising from the
use of self-completion questionnaires (although anxious mothers are likely to report more
symptoms). They also found evidence that families with whom contact was lost had slightly
higher anxiety levels, so the findings presented at the Congress might even represent an
underestimate of the overall effect.
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On the other hand, Granell concedes, the mothers’ stress was not directly measured by the
medical team, and there is no way of knowing whether their state of anxiety was transient or
chronic.
However, analysis of a small sample of the cohort by other researchers had found a
correlation between maternal anxiety during pregnancy and disrupted cortisol secretion in
children aged ten. So, as the British team reported in Berlin, bronchial hyperreactivity and
asthma in children whose mothers were stressed during pregnancy seem more likely to be
connected with hormonal imbalances in the hypothalamo-hypophysary axis than with an
allergic mechanism.
The work presented to the ERS Annual Congress is an important milestone. This is the first
prospective study on humans to examine a link between child asthma and maternal prenatal
anxiety, a relationship which appears to be dose-responsive, with the probability of asthma
increasing in proportion to the level of anxiety in the mother.
Contact:
Raquel Granell
Tel: +44 7968079410
E-mail: Raquel.Granell@bristol.ac.uk
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