"A product of the W3C Math Working Group, MathML is a low-level specification for describing mathematics as a basis for machine to machine communication which provides a much needed foundation for the inclusion of mathematical expressions in Web pages." I've never used it, but am aware of it because I use other structured files with the same .mml extension.
You might be able to reverse your workflow: prepare equations and formulæ in MathML and output an .svg (or just a bitmap) for use in Word files.
HTH!