Vitamin D Deficiency, the Canary in the Coal Mine: The Indicator of Suboptimal Health in Pregnant Women

Published on June 23, 2025

New Presentation Video with Dr. Carol Wagner: Vitamin D deficiency is the canary in the coal mine… if you are vitamin D deficient during pregnancy, you and your baby are likely to have other risk factors.

Our International Virtual Vitamin D Forum, Clearing up confusion around vitamin D: Presentations by International vitamin D researchers and experts, was held in September of 2024. The forum featured several great speakers and a lot of excellent content, but one of our intended speakers was unable to attend. Watch today’s featured video to see what she has to say on the very important topic of vitamin D and prenatal health!

This presentation with Dr. Carol Wagner reminds us of the urgent need to address poor maternal health in the United States and globally, with a particular focus on the critical role of vitamin D. The first 1,000 days—from preconception through age two—are foundational for lifelong health, and vitamin D deficiency during this time can result in detrimental effects for both the mom and baby. Black women, who experience maternal mortality rates three times higher than white women, are also up to 20 times more likely to be vitamin D deficient, underscoring a stark yet easily addressable public health disparity.

Dr. Wagner explains a unique fact about vitamin D during pregnancy and presents compelling evidence showing that maintaining maternal vitamin D levels at or above 40 ng/ml (100 nmol/L) significantly reduces the risk of preterm birth, preeclampsia, infections, and other pregnancy complications. Standard supplementation guidelines, such as the often-cited 400-800 IU/day found in prenatal vitamins, are insufficient. Given the wide variability in individual needs, Dr. Wagner stresses the importance of personalized vitamin D testing and dosing, likening it to managing any other hormone-based condition. She concludes by calling for the integration of vitamin D awareness into public health strategies, especially in maternal care, while recognizing that vitamin D sufficiency is one piece of a broader picture that includes lifestyle, nutrition, and exercise.

Watch the Video

Key Points Discussed

See YouTube video for links to specific chapters

• Poor maternal health is a pressing issue in the U.S. and globally, warranting serious attention.
• There is an array of hormonal changes and immune challenges for both the mother and her unborn child throughout pregnancy; the first 1,000 days (from preconception to age 2) are critical for lifelong health, emphasizing the need for early intervention.
• Vitamin D plays a key role in immune function, particularly during pregnancy.
• Black women face 3 times the maternal mortality rate as white women, and the rates of death among black American mothers is 55 per 100,000 live births compared to 19 in white mothers and 18 in Hispanic mothers.  Blacks are also 20 times more likely to be vitamin D deficient.
• Vitamin D deficiency is not only prevalent but preventable, making it a clear and actionable health target.
• 90% of the vitamin D that we have in our bodies is generated from sunlight exposure. So, if you have no or limited sunlight exposure, or you have darker skin pigmentation, you’re going to need more sunlight exposure to get adequate amounts of vitamin D.  It is because of this that almost everyone who does not supplement with vitamin D is deficient.
• The transfer of vitamin D occurs across the placenta; the primary form of vitamin D that is transferred to the fetus is calcidiol, or 25(OH) D, which the fetus has the capability to convert into 1,25 D, or calcitriol.  Vitamin D also transfers from the placenta to the mother.
• It is assumed that vitamin D has an effect on immune function and preventing graft versus host disease which can manifest as preeclampsia and vasculitis in pregnant women, since 50% of the fetal genes and tissue are foreign to the mother.
• Standard supplementation recommendations are too low for most individuals, especially pregnant women. While 400 IU of vitamin D3 per day can be adequate for maintaining an infant’s vitamin D status, 400 IU per day (the amount found in many prenatal vitamins) is not adequate at all for a pregnant woman and has no effect on her vitamin D status.
• Within days of conception the 1, 25 D level starts going up; by 10 weeks it’s more than double what it was during the non-pregnant state, and in most pregnant women it’s more than triple what it was before pregnancy by the end of the 1st trimester. If you saw those same levels in non-pregnant individuals, it would be toxic, they would be hypercalcemic… And yet moms and the fetus do not get hypercalcemia.
• PTH does not drive vitamin D metabolism during pregnancy, which is unlike any other time during the life cycle. The conversion of 25(OH)D to 1,25D is not optimized until 25(OH)D levels reach 40 ng/ml, indicating that as the minimum amount necessary during pregnancy.
• Intervention studies show that vitamin D repletion improves pregnancy outcomes, including reductions in preterm births.
• Women who achieved a vitamin D level of at least 40 ng/ml had the lowest risk of preterm birth, as demonstrated in several studies. Additional relationships include a lower risk of preeclampsia, hypertensive disorders of pregnancy, any infection, and overall any comorbidity.

“We know that if a woman takes 4,000 to 4,400 during her pregnancy that she’s more likely to have a really robust vitamin D status, and that women who achieve a level of around 40 ng/ml, or 100 nmol/L are more likely to have fewer adverse events during pregnancy.”

• The risk of delivering less than 37 weeks increases as 25(OH)D concentration decreases – and there appears to be a dose-response inverse relationship that has been observed in other trials
• There is significant variability in individual vitamin D needs, highlighting the importance of personalized approaches.
• Monitoring vitamin D levels is essential rather than relying on standard dosages without testing.
• Since vitamin D is a pre/pro hormone, just as with any other hormone system, it is important to measure the vitamin D level to determine what dose is needed to achieve sufficiency.  Just as an endocrinologist would not start every patient with hypothyroidism on the same dose of medication, it cannot be expected that the same dose of vitamin D will be sufficient for all.
• Integration of vitamin D awareness into public health strategies is urgently needed, especially in maternal care.
• Vitamin D Deficiency is a root cause of poor maternal health, however, being vitamin D replete does not make one achieve optimal health.  Additional pillars of health must also be addressed, including lifestyle, diet, and exercise.

About Dr. Carol Wagner

Dr. Carol Wagner is a board-certified pediatrician and neonatologist at the Medical University of South Carolina and holds the rank of Professor of Pediatrics with tenure. Dr. Wagner received her undergraduate degree from Brown University and her M.D. degree from Boston University School of Medicine with subsequent training in Pediatrics and Neonatology at the University of Rochester (NY). She came to MUSC in 1992 and has advanced along the tenure track, being promoted to Professor of Pediatrics in 2006. Her clinical questions have been the driving force for her research. For the past 24 years Dr. Wagner has partnered with Dr. Bruce Hollis to conduct vitamin D research. They have completed three large, randomized control trials of vitamin D supplementation during pregnancy and an additional two pilot studies that served as the basis for a larger vitamin D supplementation randomized clinical trial involving lactating women and their infants. Dr. Wagner has a keen interest in maternal, neonatal and infant nutrition and its effects on health and participates in ongoing clinical trials to improve maternal and infant health.

Measure Your Levels Today!

Check your vitamin D, CRP, omega-3s and 6s, magnesium, and other important markers today as part of the vitamin D*action project.

Measure your:

• Vitamin D
• Magnesium PLUS Elements (including zinc, copper, selenium, mercury, cadmium and lead)
• Omega-3 Fatty Acids
• hsCRP (for Inflammation)
• HbA1c (for Blood Sugar)
• and more

Did you know that each of the above can be measured at home using a simple blood spot test? As part of our ongoing research project, you can order your home blood spot test kit to get your levels, followed by education and steps to take to help you reach your optimal target levels. Start by enrolling and ordering your kit to measure each of the above important markers, and make sure you are getting enough of each to support better health and wellbeing!

Build your custom kit here

Start Here to Measure Your Levels

How Can You Use this Information for YOUR Health?

Having and maintaining healthy vitamin D and other nutrient levels can help improve your health now and for your future. Measuring is the only way to make sure you are getting enough!

STEP 1 Order your at-home blood spot test kit to measure vitamin D and other nutrients of concern to you, such as omega-3s, magnesium, essential and toxic elements (zinc, copper, selenium, lead, cadmium, mercury); include hsCRP as a marker of inflammation or HbA1c for blood sugar health

STEP 2 Answer the online questionnaire as part of the GrassrootsHealth study

STEP 3 Using our educational materials and tools (such as our dose calculators), assess your results to determine if you are in your desired target range or if actions should be taken to get there

STEP 4 After 3-6 months of implementing your changes, re-test to see if you have achieved your target level(s)

Enroll in D*action and Build Your Custom Test Kit!

You may also like

Does your weight affect how much Omega-3 you need? Higher Vitamin D Levels Associated with Lower Risk of Death from All Causes Dr. Michael Holick’s Prostate Cancer Diagnosis – A Video Interview Important Nutrients to Make Sure You Are Getting Along with Vitamin D