Research shows that pregnant women with lower vitamin D levels are significantly more likely to develop gestational diabetes, according to a 2026 study of 92 women. A Gram Research analysis found that vitamin D concentrations were independently associated with gestational diabetes risk, even after accounting for age and other factors. However, this observational study cannot prove vitamin D deficiency causes gestational diabetes, only that the two are connected. Larger prospective trials are needed to confirm whether vitamin D supplementation can prevent the condition.
Researchers studied 92 pregnant women to understand if vitamin D levels affect the risk of gestational diabetes, a type of diabetes that develops during pregnancy. According to Gram Research analysis, women with lower vitamin D levels were more likely to develop gestational diabetes compared to those with higher levels. The study also found that older mothers had a higher risk. While these findings are interesting, scientists emphasize that more research is needed to prove vitamin D directly causes or prevents gestational diabetes, since this was an observational study looking at existing data rather than testing vitamin D supplements.
Key Statistics
A 2026 study of 92 pregnant women found that those with lower vitamin D levels were significantly more likely to have gestational diabetes compared to women with higher vitamin D levels.
In the 2026 research of 92 pregnant women, those with gestational diabetes were on average 8 years older than those without it, with an average age of 37.55 years versus 29.21 years.
According to the 2026 study of 92 women undergoing glucose tolerance testing, advanced maternal age showed a 40 percent increased odds of gestational diabetes for each additional year of age.
The Quick Take
- What they studied: Whether pregnant women with lower vitamin D levels are more likely to develop gestational diabetes, a blood sugar problem that happens during pregnancy.
- Who participated: 92 pregnant women at a hospital in South Korea between 2016 and 2025. Half had gestational diabetes (44 women) and half did not (48 women). Women with gestational diabetes were on average 8 years older than those without it.
- Key finding: Pregnant women with lower vitamin D levels were significantly more likely to have gestational diabetes. Additionally, being older increased the risk. The study suggests vitamin D may play a role, but cannot prove it causes the condition.
- What it means for you: If you are pregnant or planning pregnancy, maintaining adequate vitamin D levels may be worth discussing with your doctor. However, this single study cannot confirm that vitamin D supplements will prevent gestational diabetes. Talk to your healthcare provider about your individual vitamin D needs and risk factors.
The Research Details
This was a retrospective study, meaning researchers looked back at medical records from pregnant women who had already been tested for gestational diabetes between January 2016 and June 2025. They compared 44 women who had gestational diabetes with 48 women who did not have it. The researchers collected information about each woman’s age, weight, and vitamin D levels from their medical records. They then used statistical analysis to determine which factors were most strongly connected to gestational diabetes. The women in the study had all taken a glucose tolerance test, which measures how well the body handles sugar.
This research approach is important because gestational diabetes affects many pregnant women and can cause health problems for both mother and baby. Understanding what factors increase risk could help doctors identify and treat the condition earlier. Vitamin D is an inexpensive nutrient that people can potentially control through diet, supplements, or sunlight exposure, making it a practical target for prevention if the connection is proven.
This study has some important limitations to understand. It looked at only 92 women from one hospital in South Korea, which is a relatively small group. Because it was retrospective, researchers could not control how vitamin D levels were measured or ensure all information was collected the same way. The study cannot prove that low vitamin D causes gestational diabetes, only that the two are associated. The researchers themselves noted these findings are observational and hypothesis-generating, meaning they suggest an idea for future research rather than proving it.
What the Results Show
Women with gestational diabetes had significantly lower vitamin D levels compared to women without gestational diabetes. In the statistical analysis, lower vitamin D concentrations were independently associated with gestational diabetes, meaning this connection remained even after accounting for other factors like age and weight. Advanced maternal age was also independently associated with gestational diabetes risk. Women with gestational diabetes were on average 37.55 years old, while those without gestational diabetes were 29.21 years old, a difference of about 8 years.
The study found that maternal age was a strong independent risk factor for gestational diabetes. For each additional year of age, the odds of having gestational diabetes increased by about 40 percent. This aligns with previous research showing that older pregnant women face higher risks of pregnancy complications.
The connection between vitamin D and gestational diabetes has been studied before, but results have been mixed and controversial. This study adds to the growing body of evidence suggesting vitamin D may play a protective role in glucose metabolism during pregnancy. However, some previous studies have found weaker or no associations, which is why larger studies are needed to clarify the relationship.
The study is small with only 92 participants from a single hospital, which limits how much we can apply these findings to all pregnant women. It was retrospective, meaning researchers relied on existing medical records rather than carefully measuring vitamin D and glucose in a controlled way. The study cannot prove that vitamin D deficiency causes gestational diabetes, only that they are associated. Vitamin D levels may have been measured at different times during pregnancy or using different methods. The researchers could not account for all factors that might affect vitamin D levels, such as sun exposure, diet, or skin tone, which affects vitamin D production.
The Bottom Line
Discuss vitamin D levels with your healthcare provider if you are pregnant or planning to become pregnant, especially if you are over 30 years old. Maintaining adequate vitamin D through diet, supplements, or safe sun exposure may be beneficial, but this single study cannot confirm vitamin D supplements prevent gestational diabetes. Your doctor can test your vitamin D levels and recommend appropriate supplementation based on your individual needs. Confidence level: Low to moderate, as this is a small observational study and larger trials are needed.
Pregnant women, especially those over 30, should be aware of this research. Women with risk factors for gestational diabetes, such as family history of diabetes or previous gestational diabetes, should discuss vitamin D with their doctors. Healthcare providers caring for pregnant women should consider vitamin D status as one factor among many when assessing gestational diabetes risk. This research is less relevant for non-pregnant individuals, though maintaining adequate vitamin D is important for overall health.
If vitamin D deficiency does contribute to gestational diabetes, correcting low vitamin D levels would likely need to happen before or early in pregnancy to have a protective effect. Gestational diabetes typically develops in the second or third trimester, so vitamin D optimization should ideally occur during preconception planning or the first trimester. Benefits would not be immediate but rather preventive over the course of pregnancy.
Frequently Asked Questions
Does low vitamin D cause gestational diabetes during pregnancy?
Research suggests an association between low vitamin D and gestational diabetes, but this study cannot prove causation. The 2026 research of 92 women found lower vitamin D levels in those with gestational diabetes, but larger prospective trials are needed to confirm whether vitamin D deficiency directly causes the condition.
Should I take vitamin D supplements if I’m pregnant?
Discuss vitamin D supplementation with your healthcare provider, who can test your levels and recommend appropriate doses based on your individual needs. While this research suggests vitamin D may be protective, it does not prove supplements prevent gestational diabetes. Your doctor can assess your risk factors and vitamin D status.
What vitamin D level is considered normal during pregnancy?
Most experts recommend vitamin D levels above 30 nanograms per milliliter during pregnancy, though optimal levels may vary. Ask your healthcare provider to test your vitamin D level and interpret results based on current guidelines and your individual circumstances.
Can I get enough vitamin D from sunlight and food alone?
Many people struggle to get adequate vitamin D from sun exposure and diet alone, especially during winter months or in northern climates. Your healthcare provider can assess whether you need supplementation based on your vitamin D blood test results and lifestyle factors.
Is gestational diabetes more common in older pregnant women?
Yes, the 2026 study of 92 women found that advanced maternal age was independently associated with gestational diabetes, with odds increasing about 40 percent per additional year of age. Women over 35 face higher gestational diabetes risk compared to younger pregnant women.
Want to Apply This Research?
- Track vitamin D intake daily through food and supplements, and log any vitamin D blood test results with dates. Record pregnancy trimester and any gestational diabetes screening test results to monitor correlation over time.
- Set a daily reminder to take a vitamin D supplement if recommended by your doctor. Log weekly sun exposure time and dietary sources of vitamin D, such as fatty fish, fortified milk, or egg yolks. Share vitamin D levels with your healthcare provider at each prenatal visit.
- Request vitamin D blood tests at preconception planning and during early pregnancy. Track vitamin D supplementation adherence weekly. Monitor gestational diabetes screening results and correlate with vitamin D levels. Set quarterly reminders to review vitamin D status with your healthcare provider throughout pregnancy.
This article summarizes research findings and should not be considered medical advice. Gestational diabetes is a serious condition that requires professional medical diagnosis and treatment. If you are pregnant or planning pregnancy, consult your healthcare provider about your individual vitamin D needs, gestational diabetes risk factors, and appropriate screening. Do not start or stop any supplements without discussing with your doctor. This study is observational and cannot prove that vitamin D deficiency causes gestational diabetes or that supplementation prevents it. Always follow your healthcare provider’s recommendations for prenatal care and testing.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.