'Dr Glenville says: ‘It makes sense to look at the ways in which our exposure to all types of oestrogen — the hormone our own bodies produce and oestrogenic chemicals we come into contact with — has changed over the years.’

‘Girls today reach puberty earlier than ever before, and are going on to have fewer ­children and breastfeeding for less time. As a result, we have far more periods than our ancestors would have had and we are exposed to more monthly surges of oestrogen, which stimulates ovulation.’

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