Vaping is inhaling the vapor from liquid chemicals heated by an electronic device. The chemicals, known as “e liquids” can be made up of a wide variety of ingredients, from nicotine to artificial fruit flavoring to distilled tobacco with the nicotine removed. As of now the products are relatively new and neither the devices or the liquids are regulated by the FDA, so there’s no way to be sure what the chemicals actually are. No long-term studies have been done on the effects of inhaled vaporized pure nicotine, or for that matter any of the other ingredients, even if they’re food-safe. And in 2009, the Food and Drug Administration studied two of the brands on the market and found toxic carcingogens including diethylene glycol (the active ingredient in antifreeze) and nitrosamines.
But, we do know for sure that smoking tobacco is extremely dangerous while you’re pregnant (and any other time) with cigarettes containing 43 known cancer-causing compounds and 400 other toxins. So while we can’t assure you that vaping anything other than pure distilled water is safe, in general vaping is definitely safer than smoking.