Quality of studies on vaping during pregnancy poor, with mixed evidence for most outcomes

Key takeaways:

• More studies reported no increased risk for adverse maternal, fetal and infant outcomes with vaping during pregnancy.
• Quality of all studies, except for the randomized controlled trial, was poor.

Studies on the risk for maternal, fetal and infant outcomes with exclusive vaping, smoking or nonuse during pregnancy have contradictory and unreliable conclusions with poor study quality, according to a systematic review.

“The most recent systematic review of studies examining evidence for the health impact of vaping in pregnancy, including 13 studies published up to February 2022, reported mixed and inconclusive findings and a call for more high-quality evidence,” Michael Ussher, PhD, professor of behavioral medicine at the Institute for Social Marketing and Health at the University of Stirling in Scotland, and colleagues wrote in BMC Pregnancy and Childbirth. “Over the last few years, there has been a proliferation of human studies on the health consequences of vaping during pregnancy and an updated review is urgently needed.”

Ussher and colleagues searched MEDLINE, Embase, CINAHL, PsycINFO, Maternity and Infant Care and the Cochrane Central Register of Controlled Trials and identified 26 studies published from 2019 to November 2023 that evaluated vaping during pregnancy with maternal, fetal and infant outcomes among 765,527 women. Researchers evaluated quality of the studies and focused on exclusive vaping compared with nonuse of nicotine and tobacco and compared with smoking.

There were 23 cohort studies, two case-control studies and one randomized controlled trial. The quality of the cohort and case-control studies was poor while the randomized controlled trial met four of five quality criteria, according to the researchers.

Most studies that compared exclusive vaping with no use of either nicotine or tobacco reported no increased risks with vaping for maternal pregnancy and/or postpartum outcomes. Vaping did increase risks for low birth weight and adverse neurologic outcomes compared with no nicotine or tobacco use.

The randomized controlled trial compared nonusers of nicotine or tobacco with women who vaped or used nicotine replacement therapy but did not smoke. The researchers reported no evidence of increased risks with exclusive vaping or nicotine replacement therapy use. Most studies that compared exclusive vaping and exclusive smoking reported similar risks for different maternal, fetal and infant outcomes.

In addition, maternal biomarker studies demonstrated a lower risk for exposure to toxicants and carcinogens with exclusive vaping vs. smoking or dual use during pregnancy.

According to the researchers, studies that found no increased risks with vaping vs. nonuse are unreliable because the substances vaped are unknown and because the studies relied on participants’ self-reports of vaping.

“These two sets of observations are somewhat contradictory and are likely due to the poor quality of evidence, which continues to limit confidence in conclusions,” the researchers wrote. “Overall, this review confirms the findings of a previous review that the studies are of poor quality, which disallows the use of meta-analysis, and the findings are inconclusive.”