Vaping During Pregnancy May Harm Fetal Skull Development

Study suggests even nicotine-free liquids could pose risks

Pregnant mice exposed to the basic ingredients found in most e-liquids developed offspring with smaller, narrower skulls. This research highlights potential risks associated with vaping, even when nicotine and flavorings are absent.

Unpacking the Ingredients

The fundamental components of vape fluids typically include a carrier liquid, most commonly a mixture of propylene glycol and glycerol (also known as vegetable glycerine). These are combined with nicotine, and various flavorings and sweeteners.

This new study, spearheaded by anatomist James Cray from The Ohio State University College of Medicine, aimed to establish a foundational understanding of how these carrier substances alone affect the body. This approach allows future experiments to isolate the impact of adding other vape components, such as nicotine.

Unexpected Findings in Mouse Study

Cray and his colleagues formulated two plain vape liquid mixtures: one with a 50/50 ratio of propylene glycol and glycerol, and another with a 30/70 ratio. Companies have recently favored higher glycerol content, partly because propylene glycol has previously been observed to increase nicotine absorption, with the aim of presenting these as safer alternatives.

Pregnant mice were exposed to the vapor from these mixtures or fresh air for four hours daily, five days a week, throughout their pregnancies. The study resulted in 140 pups from 21 litters.

Post-birth, the pups underwent detailed skull measurements and 3D reconstructions. Contrary to expectations that the higher-glycerol (30/70) mixture would show fewer negative effects, the opposite proved true.

“The 50/50 mixture had no dramatic statistical changes – and that’s where we were looking for the difference. We thought heavier propylene glycol should be causing more effects, and it was the exact opposite.”

—James Cray, Anatomist

Pups born to mothers exposed to the 30/70 fluid exhibited significantly reduced cranial and facial widths and lengths, along with shorter noses, compared to control groups. This narrowing effect extended to facial features and the cranium overall.

In 2023, over 5 million American adults reported current use of e-cigarettes, with a significant portion being women of childbearing age (CDC 2023 National Health Interview Survey).

Navigating Research Challenges

Understanding the full health implications of vaping is complex. Direct human testing is ethically prohibitive, and observational studies of long-term users require considerable time. While animal models offer a more ethical and efficient research path, their findings are not always directly transferable to human health.

The lack of stringent market regulation further complicates matters, as the precise composition of vape products can vary significantly. By isolating the effects of individual components, researchers aim to equip consumers with better information for making informed choices. This is particularly relevant given that vaping has, in some contexts, demonstrated benefits in helping individuals quit smoking.

The heating and aerosolization of vape components can also lead to the creation of novel compounds, adding another layer of complexity.

“This is a small study that speaks to the possibility that nicotine-free vaping is not safe. And it’s a sign that we probably should study the nicotine-free products as much as we study the nicotine-laden products.”

—James Cray, Anatomist

The research indicates that even nicotine-free vaping liquids may carry developmental risks, underscoring the need for thorough investigation into all types of e-cigarette products.