If you are a mom at home and think that you do not need a nanny, I am afraid you are wrong, but not because of any reason you may know about.
If you are thinking of hiring a nanny, no doubt you plan to choose her very carefully. We have all watched some of these scaring videos showing nannies bullying the children they were expected to take care of. Of course, to choose a woman who will not ill-treat your kid is the first point to consider. Fortunately, most nannies meet this requirement. So, which other points to come to?
I am not going to give you advice about things I know nothing about, or no more than any other mother. For medical advice, ask your doctor; for religious advice, ask your preacher; but for educational advice, ask a teacher.
Do the math:
One needs about a thousand hours to learn something.
The nanny is going to spend hundreds of hours with your beloved baby.
So: your baby is going to learn a lot from the nanny.
It is difficult to calculate how much time young children need to learn whatever. What we know for sure is that they learn almost continuously from any source of knowledge that they are exposed to.
Give your kid a source of knowledge that will provide him with a lifelong benefit. Hire a Polish nanny!
Polish language has a particularity: it contains most of the phonemes of the European languages; in fact all of them except the English/American sound "th" (but you are here) and the French "R", called "Parisian R".
By leaving your baby with a Polish au-pair girl regularly, you give him a gift he cannot lose or break: the ability to pronounce any phoneme without accent. There are many birth gifts but very few last lifelong.
So, even if you work at home, consider paying a Polish native speaker two hours twice a week. Your baby's future is worth it.