The Lullaby Trust condones safe co-sleeping. Crucially, it has similar guidance on cot and crib sleeping, which can also be dangerous if guidelines are not followed. As far as I’m aware, SIDS is believed to be down to a gene currently, but there’s no test and we need to wait for further research before anything like that would be possible.
Sorry to step in when not a part of this specific debate, but co-sleeping when done safely is not considered dangerous in general. Unfortunately, unsafe co-sleeping including accidentally falling asleep on a sofa or chair among many other things is included under the term, so many headlines give the impression of danger. The Constance Marten case currently being heard in court has been a frustrating one for this misrepresentation where ‘cosleeping’ is referred to, but none of it is under the safer sleeping guidance.
I coslept with my FF baby and my EBF baby and am a light sleeper who wakes easily. On a number of occasions I caught my child (literally waking at that moment) as they rolled over, despite there being bedsides so no real risk of falling. It’s an amazing experience when you follow the guidance. It did mean sacrifices for us as my DH has a sleep disorder, so didn’t share the bed (but tbh he’s a nightmare bed partner as he kicks the best every few seconds in part of the sleep cycle, so neither of us felt it was that horrific and found other time for each other, it also gave us another space to be together that wasn’t where our child was sleeping).
It can be really helpful when waking several times a night and exhausted. I think mums shouldn’t be put off by a misrepresentation of The Lullaby Trust’s perception - especially as we’ve finally moved forward with that in recent years.
The posters point on FF will have been that EBF is seen as protective in cosleeping as mothers tend to sleep more lightly. This is factual evidence, but does not mean a FF mum cannot cosleep (as stated above I did).
I think it’s a shame this thread became FF v EBF when either/or a mix are a valid choice - just as cosleeping or sleeping in a crib/cot is.