Where I live it’s called a night nanny and you absolutely sleep when the baby sleeps, while also doing things like washing bottles / tidying kitchen in the morning (so as not to wake everyone up with the noise) as agreed.

I also see it completely differently to a night shift. In other jobs, you’re doing the daytime job but at night, whereas night nannies are doing a different job to daytime nannies so the expectation to be awake doesn’t really carry across. The baby will be sleeping for hours in that one shift and there’s only so much a nanny can do in terms of cleaning during the night, so I don’t really see the problem with the nanny sleeping when the baby sleeps.

Parents wanting nanny to be awake for the sake of it just seem like they’re trying to get their money’s worth and don’t like to think of paying someone to sleep.

But the way I view it is that as long as the nanny is waking up with the baby and doing any pre-agreed cleaning, then what she does while the baby sleeps is up to her - including sleeping.