Make noindex on preprod and index on prod
prod
<meta name="robots" content="index,follow" />
preprod
<meta name="robots" content="noindex,follow" />
see how it's done on analytics of signons
prod
<meta name="robots" content="index,follow" />
preprod
<meta name="robots" content="noindex,follow" />
see how it's done on analytics of signons