In reply to Andyh83:
I climbed til 7 1/2 months outdoors and 8 1/2 months indoors. The baby took her first trip to the gym at 4 weeks!
I didn't lead (though some women do continue to lead) or boulder, and make sure the leader takes care to protect the second so there would not be any swing in case of a fall. Drop a few levels and just enjoy being outside, don't worry about the grades. Most women swap to a full body harness at around 4-5 months, there are several available, not very elegant but does the job. Carrying a heavy pack is hard once you start to show as you can't really shift the weight to your hips via the waist belt so help your friend by taking most of the gear. Avoid long approaches or very remote locations.
I was still able to climb OK right to the end, but did get much more tired faster, we could only do short days outside. In an odd way its actually very good for your technique. You can't haul yourself up over a move with your arms, so you really have to pay attention to your footwork and make small moves.
I'd really encourage your friend to try and keep climbing if she can and is comfortable doing so. Once baby arrives, with all the best intentions in the world it becomes very difficult to get out much!