Yoga when trying to conceive?

I regularly do yoga, but my husband and I have been trying to conceive for about 12 months now without success. I am currently waiting to test in 4 days time to see if we were succesful this time. I have heard that back arching and twists during the 1st trimester could be detrimental to the placenta attaching to the uterus.
Should I avoid yoga while I wait to find out if we have been succesful this month? I'd hate to think I was overstretching and thus the implantation process is affected.

Severe physical activity could prevent an embryo from attaching, or even dislodge it after attachment. Normally this is from higher impact activity, like jogging and aerobics. Yoga is typically considered a gentle low impact physical activity and though you should always check with your doctor first many women continue it during their entire pregnancy. What I would be more concerned about is your overall health. Are you too thin? Are you eating a proper diet? Are you exercising too much? Some women get that "marathon syndrome" - their bodies are so dedicated to sustaining their caloric balance which throws their hormones out of swing badly enough that they can't conceive.