Electronic cigarettes (E-cigs) are considered a safer alternative to other tobacco products — but a new study suggests that's not the case, especially for pregnant women.

The study, presented at the American Association for the Advancement of Science (AAAS) annual meeting in Washington, D.C., found e-cigarette vapors can damage an unborn child’s nervous system. The findings also showed smoking e-cigs can result in poor learning and memory.

"Because of the concept that e-cigarettes are safer than commonly used cigarettes, you may have pregnant women — and the data show this — taking e-cigarettes during pregnancy so as not to smoke, because the risk factors and the dangers of smoking cigarettes while pregnant are well-known," said lead researcher Judith Zelikoff, according to the AAAS. "That’s a frightening possibility, given the findings that are emerging."

Zelikoff and her colleagues conducted a mice study to examine pre- and post-natal exposure to e-cigarette vapors and aerosols with and without nicotine. While nicotine and non-nicotine products both produced changes, researchers found vaping products without nicotine influenced greater gene expression than products with nicotine. Specifically, they found changes in the brain associated with mental health disorders, like schizophrenia, and activity issues.

"What people don't [realize] is that even without nicotine there are many things that are given off when you heat up and vaporize these products," said Zelikoff, according to Sky News. One of the chemicals she's referring to is acrolein, a molecule that turns to vapor when heated and has been linked to cancer and lung damage.

While tobacco smoke contains a deadly mix of more than 7,000 chemicals, past research has suggested the toxic chemical acrolein contributes significantly more to the cardiovascular toxicity of traditional tobacco cigarette smoke. E-cigs have been found to contain many of the same toxins as traditional smoke, including acrolein, acid aldehyde, and formaldehyde.

Based on these findings, the British Fertility Society told Sky News it is best for pregnant women to avoid all kinds of smoking, including vaping.

"Whilst e-cigarettes may help some people to stop smoking real cigarettes, one cannot escape the reality that various chemicals are still being inhaled that have potentially harmful effects both to health, fertility and also the non-consenting participant — that is the baby," Adam Balen, chairman of the British Fertility Society, told Sky News.

This isn't the first study to question the efficacy and safety of vaping. Past studies have linked the electronic smoking devices to reduced odds of smoking and lung damage. And in some countries, vaping is banned for people under the age of 18. You can read more about the differences between smoking and vaping, here.

Source: Zelikoff J, et al. American Association for the Advancement of Science Annual Meeting. 2016.