Researchers studied whether vitamin C supplements given to pregnant women who smoke could protect their babies’ lung health. They followed 137 children to age 5 and found that mothers who took 500 mg of vitamin C daily had children with better lung function and fewer breathing problems. The study discovered that vitamin C appears to work by changing how certain genes are turned on or off in cells, specifically genes related to asthma and allergies. These changes were still visible in children’s cells at age 5, suggesting the protective effect lasts years after birth.

The Quick Take

  • What they studied: Whether giving pregnant smokers vitamin C supplements (500 mg daily) protects their children’s lungs and breathing health, and how vitamin C might work at the genetic level
  • Who participated: 137 children (ages 5 years old) whose mothers either received vitamin C supplements or placebo pills during pregnancy while smoking. About 72 children had mothers in the vitamin C group and 65 in the placebo group
  • Key finding: Children whose mothers took vitamin C had better lung function and fewer breathing problems at age 5. The study found 9 specific genetic markers that were different between the two groups, with 5 of these changes helping explain how vitamin C protected lung function
  • What it means for you: If you’re a pregnant smoker, vitamin C supplementation may help protect your baby’s developing lungs. However, the best approach is still to quit smoking. This research suggests vitamin C could be a helpful addition to prenatal care, but more studies are needed before making it a standard recommendation

The Research Details

This was a randomized controlled trial, which is considered the gold standard in medical research. Pregnant women who smoked were randomly assigned to receive either 500 mg of vitamin C daily or a placebo (fake pill) that looked identical. Neither the mothers nor the researchers knew who was getting the real vitamin C until the study ended. The children were followed from birth to age 5, with lung function tests performed at the 5-year visit.

The researchers used advanced genetic testing to examine how vitamin C affected the ‘switches’ that turn genes on and off in children’s cells. They specifically looked at genes known to be involved in asthma and allergies. This genetic testing was done on cells collected from inside the children’s cheeks (buccal cells), which is non-invasive and safe.

The study measured lung function using standard breathing tests and also tracked whether children experienced wheezing (a whistling sound when breathing) between ages 4-6. This combination of genetic analysis and clinical measurements allowed researchers to connect the genetic changes to real health outcomes.

This research approach is important because it goes beyond just measuring whether children breathe better—it tries to explain the biological mechanism of why vitamin C helps. By examining genetic switches, researchers can understand if vitamin C’s protective effect is real and lasting, not just temporary. The fact that genetic changes were still visible at age 5 suggests the benefit isn’t fleeting.

This study has several strengths: it was a double-blind randomized controlled trial (the strongest type of study design), it followed children for 5 years (long-term follow-up), and it used advanced genetic testing technology. The sample size of 137 is moderate but reasonable for this type of detailed genetic analysis. The study was registered before it began, which increases credibility. However, the study is relatively small, and results need confirmation in larger populations before becoming standard medical practice.

What the Results Show

The study identified 9 specific locations in the genetic code where vitamin C changed how genes were switched on or off in children’s cells. These changes were associated with asthma and allergy-related genes. Children whose mothers received vitamin C had better lung function measurements, specifically better airflow in the medium-sized airways of the lungs.

Five of these genetic changes appeared to be directly responsible for the improved lung function seen in the vitamin C group. Two of these changes involved a gene called SLC25A37, which helps transport iron in the energy-producing parts of cells (mitochondria). This suggests vitamin C may work partly by improving how cells use energy, which could support healthy lung development.

The protective effect was substantial enough to be measured and statistically significant, meaning it’s unlikely to be due to chance. Children in the vitamin C group also had fewer episodes of wheezing between ages 4-6, indicating real, practical health benefits.

Beyond the main findings, the study confirmed that the benefits of vitamin C supplementation during pregnancy persisted from infancy through age 5. This long-term persistence is important because it suggests the protective effect isn’t temporary but represents lasting changes in how the lungs develop. The genetic changes identified provide clues about which biological pathways vitamin C affects, opening doors for future research into other potential benefits.

This study builds on the researchers’ earlier work showing that vitamin C supplementation improved respiratory outcomes in babies born to smoking mothers. This new research adds an important piece: it explains how vitamin C works at the genetic level. Previous studies have suggested vitamin C is an antioxidant (it protects cells from damage), and this research supports that mechanism by showing vitamin C changes the activity of genes involved in protecting lungs from inflammation and allergic reactions.

The study included only 137 children, which is relatively small for genetic research. The participants were primarily from one geographic area, so results may not apply equally to all populations. The study only looked at children of smoking mothers, so we don’t know if vitamin C would have similar effects in children of non-smoking mothers. Additionally, the study measured genetic changes in cheek cells, which may not perfectly reflect what’s happening in lung cells. Finally, while the study shows association (vitamin C is linked with these genetic changes), it doesn’t prove causation with absolute certainty.

The Bottom Line

For pregnant women who smoke: Vitamin C supplementation (500 mg daily) appears to be a safe, low-cost intervention that may help protect your baby’s lung health. However, this should complement—not replace—smoking cessation efforts. The strongest recommendation remains quitting smoking entirely. Discuss vitamin C supplementation with your healthcare provider before starting. Confidence level: Moderate (based on one well-designed study that needs confirmation).

Pregnant women who smoke or are trying to quit should discuss this research with their doctors. Healthcare providers caring for pregnant smokers may want to consider recommending vitamin C supplementation as part of prenatal care. Parents of children born to smoking mothers might want to discuss whether their child could benefit from monitoring lung function. This research is less relevant for pregnant women who don’t smoke, as the protective benefit was specifically studied in this higher-risk group.

The protective effects of vitamin C appear to develop during pregnancy and persist through at least age 5. You wouldn’t expect immediate changes, but rather gradual protection of lung development during pregnancy. Benefits would likely be most noticeable in the first few years of life, though this study shows they continue at least to age 5.

Want to Apply This Research?

  • If pregnant and taking vitamin C supplements, track daily supplement intake (yes/no) and note any respiratory symptoms in your baby after birth (coughing, wheezing, breathing difficulty). This creates a personal record to discuss with your pediatrician.
  • Set a daily reminder to take vitamin C supplements at the same time each day (such as with breakfast). If you’re a pregnant smoker, use the app to track smoking reduction goals alongside vitamin C supplementation, working toward complete cessation.
  • For parents: Monitor and log any signs of respiratory issues (wheezing, persistent cough, difficulty breathing during play) in your child’s health record. Share this information with your pediatrician at regular check-ups. If your child was born to a smoking mother and received vitamin C supplementation in utero, discuss baseline lung function testing with your doctor around age 5.

This research suggests vitamin C supplementation may help protect lung health in babies born to smoking mothers, but it is not a substitute for smoking cessation during pregnancy. Smoking during pregnancy carries serious risks including miscarriage, premature birth, and low birth weight. Always consult with your obstetrician or healthcare provider before starting any supplementation during pregnancy. This study is preliminary and results should be confirmed in larger populations before becoming standard medical practice. Individual results may vary, and this information is for educational purposes only, not medical advice.