Rapidly changing landscape
Answering the question of which is safer is a challenge anyway because researchers likely have incomplete information about who vapes, who smokes, and who does both.
Still, the new research illustrates that “people are starting to think about this and beginning to do some analysis that is really hypothesis generating at this point,” Dr. Wylie said. Such studies may prompt clinicians to ask their patients about e-cigarette use. “Marijuana is sort of a similar thing where patients’ perception of safety, because things are legal, can lead to use during pregnancy without ... letting their care teams know,” she said. “Things are changing so rapidly in terms of what’s available to people to use that we need to stay on top of that as obstetricians and ask the right questions and try to understand what the risks are and potential benefits.”
Dr. Wylie is an obstetric consultant to the New England Pediatric Environmental Health Specialty Unit, which is where she heard pediatricians discussing widespread e-cigarette use among youth. It occurred to her that some of these teens eventually would be seeing obstetricians. She also saw parallels to prior research she conducted that focused on household air pollution or cooking from wood-burning fires in Africa.
“What is frightening, I think, about these electronic cigarettes is that you’re heating this liquid to extraordinarily high temperatures to create the vapor,” and the extreme heat vaporizes plastics and metals as well as nicotine, Dr. Wylie said.
An ACOG committee opinion discusses approaches to smoking and vaping cessation such as counseling, behavioral therapy, and medication.
The publication also lists a host of elements have been isolated from vape aerosol, including “carbonyl compounds (formaldehyde, acetaldehyde, acetone, and acrolein); volatile organic compounds (benzene and toluene); nitrosamines; particulate matter; and heavy metals such as copper, lead, zinc, and tin.”
In addition to the nicotine in e-cigarette liquids, which is harmful in itself, there is “all of this other company that it keeps,” including solvent byproducts, known carcinogens, and lung irritants, Dr. Wylie said. Fine particulate matter “can land in the small airways and cause inflammation, even translocate into the systemic circulation and cause systemic inflammation.”
The use of flavoring “likely alters perceptions of harm” and contributes to the popularity of vaping, Dr. Wylie noted. At the same time, the use of flavoring also has little regulatory oversight. Flavors usually are approved for marketing based on safety for ingestion, but that may not translate into safety for inhalation.
Parsing the health effects
People who vape have increased cough, wheezing, and phlegm production, compared with people who do not vape. Vaping also may worsen underlying lung disease like asthma. Lung function on spirometry decreases after e-cigarette use, studies have shown.
In 2019, researchers described e-cigarette or vaping product use–related acute lung injury (EVALI), which has caused more than 60 deaths in the United States. The condition may be related to vitamin E acetate, a component that had been used in some liquids used by patients with EVALI.
And the nicotine in e-cigarettes can accelerate atherogenesis and affect blood pressure, heart rate, and arterial stiffness.
Initially introduced as a smoking cessation tool, e-cigarettes now often are used on their own or in addition to cigarettes, rather than strictly for smoking cessation.
A Cochrane review suggests that e-cigarettes may be more effective than other approaches to smoking cessation. But “the effect is modest at best,” Dr. Wylie said. Among 100 people attempting to quit cigarette smoking, there might four to six more quitters with the use of e-cigarettes as a smoking cessation intervention, compared with other approaches.
Animal models provide other reasons for caution. One experiment in mice showed that exposure to e-cigarette aerosol impaired implantation and fetal health. The results suggest “that there might be some negative impacts across generations,” Dr. Wylie said.
Another study has suggested the possibility that women who currently use e-cigarettes may have slightly diminished fecundability. The results were not statistically significant, but the study “gives us pause about whether there could be some impact on early pregnancy and fertility,” Dr. Wylie said.
In mouse models, prenatal exposure to e-cigarette aerosol has decreased fetal weight and length, altered neurodevelopment and neuroregulatory gene expression, and increased proinflammatory cytokines. E-cigarette aerosol also has caused birth defects in zebrafish and facial clefting in frogs. Whether and how these data relate to human pregnancy is unclear.
While e-cigarette ads may convey a sense of style and harmlessness, clinicians have reasons to worry about the effects. “We have to be a little bit more cautious when we are talking about this with our patients,” Dr. Wylie said.
Dr. Wylie had no relevant financial disclosures. She is a Society for Maternal-Fetal Medicine board member and receives grant support related to research of household air pollution and pregnancy, prenatal pesticide exposure, preeclampsia in low income settings, and malaria during pregnancy. Ms. Izhakoff and coauthors had no disclosures.