Vaping and Pregnancy: Inhaled Toxins Among Reasons for Pause

Jake Remaly

June 10, 2021

Researchers are trying to understand how e-cigarette use affects pregnancy and birth outcomes. This question may become more relevant as younger vapers, among whom the devices gained considerable popularity, start having children.

Limited emerging data from animal experiments and human epidemiologic studies suggest that vaping may have negative effects on fertility and pregnancy. "Even if these impacts are less severe than conventional smoking, we really should be thinking about alternate options that may be safer for our patients than inhalation of this aerosol," said Blair J. Wylie, MD, MPH, a maternal-fetal medicine physician at Beth Israel Deaconess Medical Center in Boston.

Wylie reviewed what is known about vaping, including chemicals other than nicotine that have been detected in vape aerosols, and pregnancy at the 2021 virtual meeting of the American College of Obstetricians and Gynecologists.

"There's a lot we don't know," she said. "These products were only introduced recently, in 2003. They are marketed aggressively to our youth and have gained tremendous popularity among that population. And it's only a matter of time, I think, before we see a lot of use in our own patient population."

In a separate study presented at the ACOG meeting, Nicole Izhakoff, a researcher at Florida International University, Miami, and colleagues evaluated the association between e-cigarette use during pregnancy and unfavorable birth outcomes, such as preterm birth, low birth weight, or extended hospital stay for the newborn.

The investigators used 2016-2017 survey data from the Pregnancy Risk Assessment Monitoring System. In all, 71,940 women completed the survey, including 859 who reported e-cigarette use during pregnancy.

After adjusting for age, race, ethnicity, insurance, maternal education, prenatal care, abuse during pregnancy, and complications during pregnancy, the researchers estimated that the odds of an unfavorable birth outcome were 62% greater among women who used e-cigarettes during pregnancy, compared with those who did not.

The researchers lacked information about simultaneous use of alcohol, traditional tobacco, or other drugs, however.

"Physicians of all subspecialties, especially those of obstetrics-gynecology and pediatrics, need to increase the implementation of screening for past or current e-cigarette use in at-risk patients," Ms. Izhakoff and coauthors concluded. "Further research regarding the long-term health effects of e-cigarettes is warranted."

Wylie coauthored another study related to this topic that was published online May 24, 2021, in the Journal of Maternal-Fetal & Neonatal Medicine.

The researchers examined birth weights of children whose mothers use e-cigarettes alone, those whose mothers used both e-cigarettes and conventional cigarettes, and those whose mothers smoked conventional cigarettes only. Their estimates were imprecise, but signaled that e-cigarette use may reduce birth weight. The use of e-cigarettes alone appeared to have less of an impact on birth weight than the dual use of conventional cigarettes and e-cigarettes did.

Wylie cautioned that outcomes like birth weight are "pretty crude measures of whether an exposure is okay or not in pregnancy. Many of these toxins that we know that are in the aerosols can cause harm, but they may not be reflected in the absolute value of the birth weight."

In addition, clinicians should avoid focusing on the wrong question when caring for patients.

"I think the wrong question is: Is vaping safer than smoking?" Wylie said in an interview. "Metals are going into your lungs. Plastics are going into your lungs. It is hard for me to think that we are going to identify that as our champion smoking cessation strategy in pregnancy."

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," 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."

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, 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, 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, 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," 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," 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," 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," Wylie said.

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.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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