Sometimes your merge template can contain a formatting switch that causes unexplained formatting, such as bold text, font size changes, or italicized text.
In the merge template document, remove the formatting switch located in the code. ( \* mergeformat ) by finding it and highlight and delete. You can also do a Find\Replace.
Note: You must save the document with Print Field Codes on (press Alt+F9) so that you can see the code.