Should I Stop Retin-A Treatment Before Having IPL?

Thanks for your question.
Retin A is an excellent anti aging treatment and is a key part of most anti-aging regimens. In regards to its usage before IPL, you should really have to problems, and in fact, I believe that its continual usage before and after the procedure will actually lead to better IPL results, especially with for the treatment of hyperpigmentation.
When doing lasers, it is not uncommon for physicians to put patients on Retin A or Hydroquinone, or a combination of both, 2 weeks prior to and for 2 weeks after the procedure. You can feel comfortable using the Retin-A knowing that your results will not be affected at all, and may actually be improved just continuing what you've been doing all along.
The only other preparation I would do prior to your IPL is to practice fairly strict sunavoidace 2 weeks prior and 1 week after your procedure, and to wear a fairly strong SPF 15 or 30 sunscreen throughout this entire time.
Good luck!