Stevia is not currently considered safe for women who are pregnant or plan to become pregnant. Neither are Truvia or Purevia, the only two sweeteners derived from stevia currently on the market. It's not that any of the three are known to be dangerous or unsafe for pregnant women, rather there is no evidence to support or deny its safety at this time. Given the absence of scientific data proving that Stevia is safe, organizations like the FDA and the American Dietetic Association (ADA) will not recommend the use of stevia as a sweetener to pregnant women. Technically, neither stevia nor its derivatives are approved by the FDA for use by anyone. The FDA declined to object when Coke and Pepsi, the makers of Truvia and Purevia asserted that they were going to start using those sweeteners in their products.
Safe Artificial Sweeteners
Many of the other currently available artificial sweeteners are approved for use by pregnant women by the FDA, when consumed in moderation. Splenda (sucralose) is considered safe, as are products containing Sunett (Acesulfame Potassium). Though Nutrasweet and Equal (aspartame) also meet the FDA's guidelines for use by pregnant women, there are some OBGYNs who will not recommend its use.
Questionable Artificial Sweeteners
Saccharin, though considered safe for normal consumption, is known to cross the placental barrier and may remain longer in fetal tissue than it does in the mother's body. There are no known pregnancy issues related to saccharin, but as with tevia, a lack of evidence proving that a product is unsafe is not enough for the FDA to pronounce a product safe. Cyclamates is another questionable sweetener, banned in the United States, but available in Canada and the United Kingdom.