In reply to LPA:
Hi and congratulations!!
I climbed throughout both of my pregnacies. Personally I bouldered to about 12 weeks then just top roped until it stopped being fun which was about 8 months the first time and 6 and a half the second.
The advice is (as with any exercise) to listen to your body and not push too hard. I found this very difficult as my body no longer felt like my own and I had no idea what was normal and what wasn't but I persevered. Some days I climbed as well as I would have done pre pregnancy (woohoo for hormones) and some I would climb appalling but enjoyed it all the same. I was careful not to do anything dynamic or to overstretch due to the relaxin in your body making tendons more loose. In the end it was PGP which stopped me climbing both times, I just became too uncomfortable and wasn't enjoying it any more.
i had a petzle pregnancy climbing harness the first time around and just a standard full body harness the second. I'm not sure about specific guidance around how they should fit, I just made sure that I was secure and that nothing was pressing or going to press when weighted on my bump.
Just a note on post birth... Do your pelvic floor exercises!!! Boring but true and it will help. Again listen to your body and when you feel ready to back. For some that might be a couple of months, for me I needed some sense of normality and I went back within a couple of weeks both times, it was very gentle and I spent more time sat feeding than I did climbing but I loved being back in that space. I suppose what I'm saying is do what is right for you within what is safe.
There's a great podcast I think it's Hazel Findlay talking to Rachel who set up Rock Tots about climbing and pregnancy/post birth/with kids.
Beth Roden wrote a lot about climbing pregnant if you go back through her archives (her son was born in 2014).
Different sport but I found Jo Pavey's book interesting and useful (this mum runs).
The women's climbing symposium had a session on climbing when pregnant last year, not sure if any of the resources from that are on the resources Facebook group.
ENJOY!