No significant risk. Artificial sweeteners do not pose a significant risk to your health, and do not lead to any demonstrated increase in risk of harm to your baby. Still, during early pregnancy, many women choose to avoid artificial sweeteners as part of a plan to avoid all chemicals, medications, over the counter remedies, herbals, and additives in their diet.
Not in humans. Artificial sweeteners are regulated by the fda in the us. The ones that are commercially used at this time have not been linked to an increase in human cancers. However, there was link found with saccharin and bladder cancers in rats, and aspartane and brain tumors in rats. However, this was at doses that were very high compared to that consumed by humans. Also the metabolism is different in rats.