I'm 16 weeks along but showing far more than that! and recently got waxed.
I just explained to the girl that there were just some positions impossible for me to manage and she adjusted them to ones that I could do...
When you ring up, just mention you are pregnant and generally they will book you with someone experienced in waxing pregnant women.
I will continue getting waxed because well - I can't manage my legs because I get so breathless and nearly pass out and as for the bikini line - I don't want to do it by feel!
Hope that helps!