Nicotine Exposure Before Birth May Weaken Immunity For Years: Study

Nicotine exposure during pregnancy may have consequences that extend far beyond birth, potentially affecting how the body fights respiratory infections years later. A new study by researchers at the University of California, Santa Cruz, has found that nicotine exposure during pregnancy and shortly after birth altered immune system development in mice, making them more susceptible to severe influenza infections in adulthood.

The findings, published in Stem Cell Reports, offer fresh insight into how early-life exposures may shape long-term health. They also raise important questions for public health, particularly in countries such as India, where tobacco use remains widespread and smokeless tobacco is common among women.

The study does not establish that nicotine exposure produces the same effects in humans. However, it provides a possible biological explanation for the increased vulnerability to respiratory illnesses observed among children exposed to tobacco during pregnancy.

The research team, led by Professor Camilla Forsberg’s laboratory at UC Santa Cruz, examined how nicotine affects blood-forming stem cells, known as haematopoietic stem cells (HSCs). These cells produce the blood cells that support immunity and help the body respond to infections.

Using mouse models and cell-tracing techniques, the researchers found that offspring exposed to nicotine during pregnancy and shortly after birth had fewer blood-forming stem cells. Changes in the activity of genes regulating immunity also persisted into adulthood, even after exposure had ended.

Although some blood-cell changes appeared to diminish as the animals grew older, their lungs retained fewer resident macrophages. These immune cells help clear harmful particles and pathogens and provide an early line of defence against respiratory infections.

The researchers then exposed the mice to the influenza virus to assess how their immune systems responded. Animals exposed to nicotine early in life developed more severe infections, with greater lung inflammation, increased immune-cell movement into lung tissue and more extensive lung damage. They also experienced greater weight loss.

The findings suggest that early nicotine exposure may leave a lasting biological imprint that becomes apparent only when the immune system encounters an infection.

Marcel Rommel, a postdoctoral researcher at UC Santa Cruz and one of the study authors, said the research focused specifically on nicotine rather than the many other compounds found in cigarette smoke.

This distinction matters because nicotine is present not only in tobacco products but also in newer nicotine-delivery products. By studying nicotine separately, researchers sought to understand whether it could affect immune development independently of other substances in tobacco smoke.

However, the study does not establish that all nicotine-containing products produce identical effects or that the findings in mice can be directly applied to human pregnancies.

But the findings matter for India given its tobacco burden. According to the Global Adult Tobacco Survey (GATS-2), conducted in 2016–17, 28.6% of adults aged 15 and above used tobacco, including 10.7% who smoked and 21.4% who used smokeless tobacco. The World Health Organization estimates that nearly 267 million adults in India use tobacco. These figures describe tobacco use, not nicotine consumption alone, and remain the latest widely cited national GATS estimates. WHO India and GATS-2.

The challenge extends to pregnancy. An analysis of India’s National Family Health Survey-5 data, published in The Lancet Regional Health – Southeast Asia, found that 2.5% of currently married pregnant women and 3.2% of lactating women reported using tobacco. More than 85% of tobacco users in both groups consumed smokeless tobacco.

Products included gutkha or paan with tobacco, khaini and other chewing tobacco preparations.

These figures underline why maternal tobacco prevention cannot focus on cigarettes alone. Smokeless products may be used in homes and communities where smoking is less socially acceptable, creating a risk that their health effects are underestimated.

The findings could help researchers identify biological pathways linking early-life exposure to respiratory disease later in life.