Hi Julie,
I'm answered "2nd trimester", but I guess I feel the need to qualify my answer. I maintained my weight load for the first 10 weeks of my pregnancy, which is when I developed the torn placenta and was put on bedrest. I remember at that time that I was on the point of considering that I needed to reduce my leg weight loads; I was getting very breathless.
Once my 9 weeks of bedrest were over, I was well into the 2nd trimester, and the extended period of inactivity obviously required that I start back with lighter weights than before. I'm now going one weight increment lighter on my upper body weights, but have cut my lower body weight loads in half.
Sandra