When is an IUI needed????

So my gyn feels an <a href="https://glowing.com/glow-fertility-program">IUI</a> might be needed we are ttc for about 7months now, I'm 42yrs old and my fiancé is 32yrs old... When is an <a href="https://glowing.com/glow-fertility-program">IUI</a> needed though and why?