Evidence not yet sufficient to change practice but findings warrant further
investigation, say researchers

Date:

October 4, 2017

Source:

BMJ

Summary:

Taking
multivitamins during early pregnancy may be associated with a reduced risk of
autism spectrum disorder (ASD) in children compared with mothers who do not
take multivitamins, finds a study.

The researchers stress
that their findings cannot establish cause and effect, but say they raise
questions about a possible association that warrant further investigation.

Autism spectrum disorder
(ASD) includes a range of conditions, including Asperger syndrome, that affect
a person’s social interaction, communication, interests and behaviour. It’s
estimated that about 1 in every 100 people in the UK has ASD. More boys are
diagnosed with the condition than girls.

Research indicates that
ASD most likely develops in the womb and that a mother’s diet during pregnancy
could have an influence. But results from previous studies have been
inconsistent, suggesting that other unmeasured factors (confounding), such as a
mother’s overall health and lifestyle, could also play a role.

So an international
research team set out to assess whether nutrient supplementation during
pregnancy is associated with reduced risk of ASD, with and without intellectual
disability.

They applied three
analytical methods to a sample of 273,107 mother-child pairs living in
Stockholm, Sweden. The sample was restricted to children who were 4 to 15 years
of age by December 31 2011 and were born between 1996 and 2007.

Women reported their use
of folic acid, iron, and multivitamin supplements at their first antenatal
visit and cases of child ASD were identified from national registers.

After adjusting for
several potentially influencing factors in both mothers and children, the
researchers found that multivitamin use, with or without additional iron and/or
folic acid, was associated with a lower likelihood of child ASD with
intellectual disability relative to mothers who did not use folic acid, iron,
and multivitamins.

There was no consistent
evidence that either iron or folic acid use were associated with a reduced risk
of ASD.

The results of the
various analyses seemed to be consistent with each other, say the authors,
suggesting that the association between multivitamins and ASD might not be
fully explained by confounding.

They point to several
study limitations, such as the potential for confounding and difficulty
assessing type, timing and dose of supplements. However strengths included the
relatively large population-based sample size and the advanced analytical
methods used to gauge the robustness of findings.

“Together, the three
analyses appear to point toward a potential inverse association between
multivitamin use with ASD with intellectual disability,” say the authors.

Given the current
understanding and strength of evidence supporting the importance of nutritional
supplementation during pregnancy, “it is impossible to imagine that these
results, on their own, should change current practice,” they write.
However, they say these findings “raise questions that warrant
investigation” and call for verification in randomised studies
“before recommending a change to current practice.”

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Journal Reference:

1.    Elizabeth A DeVilbiss,
Cecilia Magnusson, Renee M Gardner, Dheeraj Rai, Craig J Newschaffer, Kristen
Lyall, Christina Dalman, Brian K Lee. Antenatal nutritional supplementation
and autism spectrum disorders in the Stockholm youth cohort: population based
cohort study. BMJ, 2017; j4273 DOI: 10.1136/bmj.j4273