The researchers then looked at the gene expression patterns of the uterus.
“When we saw the delay in implantation, we presumed that there must be something wrong in the ability of the fertilized egg to attach to the womb,” Caron said.
Wetendorf found there were significant changes in gene expression in key pathways that are known to regulate that attachment process — not only in mice, but also in humans, Caron said.
“If you can extrapolate or think about long-term consequences, when a young woman is vaping, she is changing the ability of her uterus to express those genes that are important for embryo implantation,” Caron said.
A key aspect of the study was its design. The researchers designed the vapor to be as simple as possible by only using nicotine and a carrier chemical PG/VG (propylene glycol and vegetable glycerin). They did not add any additional chemicals or fillers to the compound, Caron said.
“The e-cigarette delivery devices are commercialized to be nicotine replacement or cessation devices, so we tend to focus just on the nicotine," Caron said. "But most people are vaping with a very complex mixture of flavors and additives. All of those things are known to be very toxic, particularly when they are combusted and inhaled.”
Caron also said that e-cigarettes are not regulated by the U.S. Food and Drug Administration, meaning that there is no quality control or standardization of the cartridges.
“The implications for that is obviously that this e-cigarette exposure could obviously impair fertility or maybe a woman’s chance to get pregnant," Wetendorf said. "Then, the exposed fetus could potentially have some long-term implications that are not necessarily seen immediately."
The mice used in the study were of equivalent age to a young adult female who would have used e-cigarettes for two to three years on most days, Caron said.
“If we can see second-generation effects of vaping on offspring later in life, it's certainly possible that vaping can have long-term consequences on one’s physiology and genetics that we just don’t know now,” Caron said.
The detrimental effects on the physiology of the mice were not exclusive to females, she said.
“For those mice that were exposed in utero, there was a slight impairment in male offspring, in their fertility," Caron said. "Interestingly, the females that were exposed in utero exhibited long term metabolic defects in life, and they had a reduced weight at 8.5 months of age."
Caron said other studies are showing more second-generation offspring effects including cognitive and behavioral defects; defects in the cardiovascular system and the kidneys; and influences on the immune system.
The results of the study also show that the offspring of women who vape while pregnant are also at a higher risk of developing metabolic disorders, impaired reproduction and growth restrictions.