@jw - have you set Word's options to not resize images. How to do that varies between versions. Suggest you search for "Stop Word nnnn Resizing Pictures".
On Word 2003/2007 changing the settings will only affect new image insertions, any existing images will have to be reinserted. Not sure about 2010/2013.
IMO Word isn't the best authoring tool if the book contains lots of different images and the primary target is a flowable format (eg epub, mobi etc). At it's core Word is a fixed format editor, so it's at its best if you're targeting print or PDF, where resizing images makes sense.
One alternative approach might to insert markers in the text to identify which image goes where, and then replace the markers with the images using an ebook editor, such the calibre ebook-editor or Sigil.
BR
|