Altitude and Pregnancy

I'm a first time mom, currently 5 weeks pregnant and I'm wondering about altitude and pregnancy. My brother is doing the Pikes Peak Ascent this weekend and I want to go watch. I've lived in Colorado all my life so altitude has never been a problem for me but I've also never been that high up. I also have asthma but it's not too severe. I have an inhaler I can take if needed. What's everyone's thoughts? I haven't told my family yet and wanted to wait till 8 weeks at least.