I have never had a nanny for an infant. The youngest any of my kids were left with a nanny for a full day was 6 months. So I can't answer that question. I imagine it would be such a difficult job that only very special and capable nannies would take on nannying high maintenance infants. All my kids were extremely hight maintenance as infants and I barely coped I couldn't imagine asking a nanny to.
The child in the OPs case is 14 months old. Not an infant.