Best practice for abbreviated words in navigation links?

For our site main nav, when a smartphone user enlarges font size, I'm considering switching the text of nav items to an abbreviated "short text" version, e.g., "Continuing Professional Education (CPE) Evaluations" would switch to appear as "CPE Evals". For accessibility, should I have a screen reader read the full text and ignore the short text - or just let the screen reader read the short text? In some cases, the abbreviated text will sound weird when read aloud, e.g., "Orntn" for "Orientation"