June 6, 2018

expert reaction to study investigation the association between hypertensive disorders in pregnancy and neurodevelopmental disorders in children

A study, published in JAMA Psychiatry, reported an association between hypertensive disorders in pregnancy and neurodevelopmental disorders such as autism and ADHD in children.

Dr James Cusack, Director of Science, Autistica, said:

“This study is one of many to find a relationship between altered neurodevelopment and events during pregnancy.

“The researchers reviewed the research evidence and found that mothers who have hypertensive diseases, such as pre-eclampsia, have a slightly increased likelihood of their child being autistic or having other neurodevelopmental conditions.  This does not mean that having a hypertensive disease during pregnancy causes autism or altered neurodevelopment, it only means there is a slight association.

“The researchers recommend increased monitoring of the child on the basis of this finding.  I am not convinced that with such a small increase in the likelihood of autism, that increased monitoring is appropriate.  It could also unnecessarily concern parents.”

Dr Judith Brown, Head of Autism Knowledge & Expertise, National Autistic Society, said:

“There are around 700,000 autistic people in the UK and, although the exact causes of autism are still not fully understood, research to date has shown it involves many complex and interacting factors, including genetics, the environment and the development of the brain.

“This review has looked at all available studies on hypertension disorders in pregnancy and autism. Although there appears to be a small association between maternal hypertension and autism, as the authors acknowledge, these are all observational studies and other factors that may have contributed to this apparent association have not been explored. We don’t believe the findings would justify targeted screening of children born to mothers who had the condition in pregnancy.

“While it is important to understand the causes of autism, we believe more research should be focused on what helps autistic people and their families so that all autistic people can have a good quality of life and get the support and understanding they need.”

Prof Dorothy Bishop, Professor of Developmental Neuropsychology, University of Oxford, said:

“This looks like a well-conducted study that aggregates results from the literature to explore whether there is any association between hypertension in pregnancy (including pre-eclampsia) and subsequent neurodevelopmental disorders in childhood, including autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD).

“It would be good if studies like this could report their results in terms that nonspecialists can understand: by my calculations, their figures indicate that ASD affects around 1 in 86 children whose mothers were hypertensive, compared with 1 in 116 who were not hypertensive; ADHD affects around 1 in 30 children of hypertensive mothers as compared with 1 in 38 other mothers. These figures make it clear that the vast majority of children born to hypertensive mothers will not have ASD or ADHD.

“This does not mean the findings are unimportant: the association is based on very large numbers of cases, across several large studies, and it needs explaining. The difficulty is knowing whether there is a direct risk because of the biological impacts of hypertension, whether there may be adverse effects caused by drugs used to treat it, or whether there is some other factor associated with hypertension (such as social background) which may be involved. The fact that one large study from Australia found lower rates of ASD in children of hypertensive vs nonhypertensive mothers emphasises that there are many aspects of this association that are unexplained. Where possible, the studies reviewed here controlled for factors that might lead to a spurious association, but it is never possible to be clear about what causes what in observational studies. The authors are appropriately cautious in noting these possibilities.

“I am not convinced that their results justify their call for screening of children born to mothers with hypertension, especially since is it unclear what intervention would be effective, and there is potential to cause anxiety in parents.”

* ‘Association of Hypertensive Disorders of Pregnancy With Risk of Neurodevelopmental Disorders in Offspring: A Systematic Review and Meta-analysis’ by Maher et al. will be published in JAMA Psychiatry at 16:00 UK time on Wednesday 6 June, which is also when the embargo will lift. 

Declared interests

Dr James Cusack: No conflicts of interest

Prof Dorothy Bishop: I declare that I have no conflicts of interest.

None others received.