Who knows twelve?
Please cite/link your sources, if possible. After about one business day, I will:
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"Twelve" is a common mistake people make when encountering the Biblical term for eleven, עשתי עשר
Twelve months is the maximum length of a human pregnancy (Shulchan Aruch, Even HaEzer 4:14).
Interestingly, there are a number of places in Chassidus (for example, here) where it is stated that the prophet Eliyahu was born after a pregnancy of this length.