The Gemara14 relates that “Kimchis had seven sons, all of whom merited to serve as Kohanim Gedolim, High Priests. The Sages asked her, ‘What have you done to merit this?’ She answered them: ‘The rafters of my house have never seen the plaits of my hair.’ “
This is the main reason chassidishe women shave their hair. To have good children.