I still don’t understand this...

DL 👩🏻👨🏽‍🦱💉🌈💙

When taking progesterone after <a href="https://glowing.com/glow-fertility-program">IUI</a>, why do doctors want you to stop if bfn at 14dpiui knowing that you may not have missed your period yet and some women don’t get a bfp until a week after missed period. I can’t find any explanation for it. Any ideas?