Use Word's StyleRef field to repeat content throughout a document, including in the header and footer.

The Header in Word is used to repeat content on top of every page, while the Footer is used to repeat content at the bottom. Learn how to use it.

Alternatively, you could put the header row data in the document header. Thereby avoiding having to redo it every time. Merging into tables is a huge PITA, especially for a repeating report.