A family of Microsoft word processing software products for creating web, email, and print documents.
Work in .docx!
If you work in the obsolete .doc format, picture quality will often be reduced to accommodate the limited capabilities of the obsolete format.
You could also ignore the problem :-) When you resize a picture within Word, it creates a new "display" version of the picture. That's at much lower resolution, to save file size. It will print from the high-DPI original version which remains stored in the file.
If, instead, you resize the picture externally before inserting into Word, that down-sampling will not be necessary and what you see on screen will retain its sharpness.
However: the screen display is reduced: not to 72 dpi, but it's less than 150. If you have a retina display, you will see the difference. The printout should be OK.
Hope this helps