Vaping and e-cigarettes before trying to conceive

What does the evidence say about vaping and e-cigarettes before trying to conceive while trying to conceive?

1. In animal studies, e-cigarette vapor exposure, even from nicotine-free liquids, caused circulating testosterone to drop by 30 to 50 percent through reduced expression of enzymes needed for hormone production, along with a significant decrease in sperm count and viability. 1
2. Specific e-cigarette flavorings damaged reproductive cells in laboratory studies, with cinnamon flavor affecting sperm movement and bubble-gum flavor destroying the cells that produce sperm, while e-cigarette vapor also altered genes involved in uterine receptivity and delayed embryo implantation by 3 to 4 days in exposed mice. 1
3. In a human study of women undergoing assisted reproduction, clinical pregnancy rates were similar whether they didn't smoke (40.6 percent), smoked cigarettes (36.1 percent), or used e-cigarettes or hookah (40.5 percent), though nicotine byproduct levels were far lower in vapers' follicular fluid than in smokers', and researchers cautioned that vaping liquids still contain potentially harmful substances that need more study. 2
4. E-cigarette use during pregnancy has been linked to a higher chance of preterm delivery and low birth weight, one study found a possible link between pre-pregnancy e-cigarette use and gestational high blood pressure, and evidence on miscarriage is mixed, with one study finding a link and two others not. 3
5. Nicotine passes into breast milk and may affect a nursing infant's heart rate and blood pressure, and animal studies suggest nicotine and e-cigarette flavoring ingredients can change the ovaries in ways that could affect fertility, though no human studies have directly tested whether e-cigarette use affects the ability to conceive. 4

What to know about vaping and e-cigarettes before trying to conceive while trying to conceive

• Animal research is the main evidence base so far, and it's not reassuring: e-cigarette exposure, including nicotine-free liquids, has been linked to a 30 to 50 percent drop in circulating testosterone in males along with lower sperm count and viability, and to changes in genes that affect uterine implantation in females.
• The one human study to look at actual assisted-reproduction outcomes found no significant difference in pregnancy rates between e-cigarette or hookah users and nonsmokers, though the researchers still flagged vaping liquids as containing potentially harmful substances and called for larger, longer studies.
• If vaping continues into pregnancy, it's been linked to a higher chance of preterm delivery and low birth weight, and nicotine passes into breast milk if you're vaping while nursing. Quitting before you start trying removes these questions from the table entirely.