I say go for it! I was extremely active before my pregnancy, I even did a 10 mile mud run, crawling through muddy water, tight ropes and all sort of hard obstacles. I am currently 30 weeks pregnant and in great shape!
Pregnancy only lasts a short time. You have one job at this moment and in my opinion, that's taking care of that child. The hiking doesn't sound like the issue... but the 25lbs and remote area are scary. I'm 38 and pregnant with my 1st. I'm considered high risk because of my age (advanced maternal age). I would ask my Dr before making the hike. Good luck!!
You should be just fine. Just rest when your body says rest and drink, drink, drink water. I hiked through some Flagstaff hills with my last pregnancy and I know I didnt drink enough, but felt ok at around 4 mos preg. Im from CO, so the hike was fine, but it is more exerting.
I've heard if you were active before your pregnancy then It's fine to stay active through pregnancy, but if something begins to feel uncomfortable then I would try & take it easy. Just be careful, make sure you eat a snack every 2-3 hrs & drink plenty of water. Good luck!