Half marathon goal adjustment for pregnancy

long time lurker- first time poster. I am signed up to run my 3rd half marathon next month! I had a great training block in the fall and ran around a 1:55 feeling like I still had gas in the tank at the end so I came into the spring excited to crush that time. 12 weeks into my 16 week block my runs started feeling SO hard, heart rate 15 beats higher than normal on my easy runs and goal pace completely wiping me out after only a couple miles. sure enough- positive pregnancy test.

I’m hoping to still do my half marathon and I’m sure OB will be fine with it given I’ve been training for months (already completed 2 11+ mile runs) and I’ll only be 8/9 weeks at race day, but I am having a really hard time figuring out how to go out and pace myself. I don’t want to set out way too fast and totally die but I also would love to still have a goal for my own motivation.

luckily I still have a month to try some different paces on my long runs but I’d love advice on how to adjust training and my race plan. I had been doing a mix of easy runs, long runs, speed work and some tempo (above race pace) work. I’m not sure if I should switch to all “easy” runs or even really sure what pace is easy anymore.

I can also still defer the race if first trimester hits too hard but I’m hoping to do it!