Researchers have identified a link between exposure to high levels of oestrogen sex hormones in the womb and the likelihood of developing autism.
Published in the journal Molecular Psychiatry, the discovery adds further evidence to support the prenatal sex steroid theory of autism first proposed 20 years ago.
In 2015, the researchers measured the levels of four prenatal steroid hormones, including two known as androgens, in the amniotic fluid in the womb and discovered that they were higher in male fetuses who later developed autism.
These androgens are produced in higher quantities in male than in female fetuses on average, so might also explain why autism occurs more often in boys. They are also known to masculinise parts of the brain and to have effects on the number of connections between brain cells.
Now, the same scientists have built on their previous findings by testing the amniotic fluid samples from the same 98 individuals sampled from the Danish Biobank, which has collected amniotic samples from over 100,000 pregnancies, but this time looking at another set of prenatal sex steroid hormones called oestrogens.
This is an important next step because some of the hormones previously studied are directly converted into oestrogens. All four oestrogens were significantly elevated, on average, in the 98 foetuses who later developed autism, compared to the 177 foetuses who did not.
Contrary to popular belief that associates oestrogens with feminisation, prenatal oestrogens have effects on brain growth and also masculinise the brain in many mammals.
(At The Quint, we are answerable only to our audience. Play an active role in shaping our journalism by becoming a member. Because the truth is worth it.)