Tricky question. See, taking in sufficient protein is one thing, taking in excess protein/aminos now isn't necessarily the best thing, and its not just about the baby. You have to remember that your body is now handling the waste byproducts for you and the baby, as well. Excess protein has the potential to put a strain on your kidneys.
Additionally, as much as you might
want to continue your current workout regime, your body has a way of telling you what IT wants (and if you don't listen it will MAKE you listen). Additionally, and this may sound like I'm stating the obvious but until you go through it you just don't get it, pregnancy does
weird things to your body, your joints begin to loosen, not just the pelvic ones but ALL of them, you hold water, your hormones are completely different from any other time of your life, your physical geometry starts to change. Being pregnant is just plain weird (despite the fact its what our bodies are designed to do, there's no getting around the fact you get turned from a woman into an incubator). The hormonal shifts alone will make it difficult to maintain muscle mass.
I think you might find this article interesting, it touches on all aspects of weight training and mentions supplements, as well:
Weight training during pregnancy :: stumptuous.com