I took three months off each time. I suspect I'd have been very sub-par in a work context as like others have mentioned, the overriding change was lack of sleep. We definitely felt zombie-like for some good proportion of that time. Perhaps the extra brain matter was trying to compensate for running on empty? :)

We organised with me as evening shift - so mum could get a little uninterrupted sleep, and she picked up the morning shift.