Vitamin D usually comes up in conversations about bone health, calcium absorption, or immune function. But it plays a role in so many aspects of fertility, conception, pregnancy and foetal development.
Why is vitamin D important during pregnancy?
This nutrient is involved in numerous processes within the body that ensure a healthy pregnancy, including:
- Aiding implantation
- Supporting foetal growth and skeletal development
- Regulating placental function & placental hormone levels
- Limiting production of proinflammatory cytokines
- Regulating blood sugar and insulin levels
- Promoting maturation of foetal lungs
- Maintaining endothelial integrity/membrane stability (this is important for regulation of blood pressure, among other functions)
Research has shown that those who maintain adequate vitamin D levels during pregnancy have a lower risk of many pregnancy complications, including:
- Gestational diabetes
- Preeclampsia
- Preterm birth
- Bacterial vaginosis
- Small for gestational age babies
One of the most compelling findings is related to preterm birth. In one study, mothers with adequate blood levels of vitamin D had a 60% lower risk of preterm birth. This finding held true even after adjusting for many confounding factors, including race. In women of color, the reduced risk of preterm birth was a shocking 78%.
Let’s look more closely at foetal brain development
That’s an area where Vitamin D is getting more attention, with a recent study following 289 mother-child pairs examined whether maternal Vitamin D status in pregnancy was associated with children’s neurocognitive function at age 4l (PMID: 40731094) Maternal serum 25(OH)D was measured in the first and third trimesters, and children were later assessed using standardized tests of IQ, working memory, visual-motor skills, language, emotion recognition, and executive function.
A few key findings stood out:
- Vitamin D insufficiency was extremely common. Only 16.6% of mothers had sufficient 25(OH)D levels in the first trimester and only 14.9% were sufficient in the third trimester, using the already very low cutoff of >50 nmol/L (>20 ng/mL).
- Lower vitamin D across pregnancy was linked to poorer visual-motor precision.
- Third-trimester vitamin D deficiency was associated with lower working memory scores, even after adjusting for confounders.
- Third-trimester vitamin D deficiency and insufficiency were also associated with more parent-reported executive function difficulties, especially inhibition and working memory.
Mechanistically, this makes sense. The prefrontal cortex undergoes rapid development in the second and third trimesters, and vitamin D is involved in neurogenesis, neuronal differentiation, synaptogenesis, myelination, and neurotransmission.
Important caveat: this was observational, so it cannot prove causation. The study also lacked data on maternal sunlight exposure, season of blood draw, and children’s serum vitamin D levels.
Still, these findings add to a growing body of evidence that adequate vitamin D in pregnancy may matter for more than skeletal health, and that it’s worth checking vitamin D status rather than assuming levels are adequate.
Vitamin D is a complex nutrient/hormone, and there’s no one-size-fits-all dose. But the research is clear that we need to be paying closer attention to vitamin D status in pregnancy.
Ensuring good levels of ALL nutrients well BEFORE conception remains a grounding factor in successful conception, full-term pregnancies and infant health.
You willl find a great deal of helpful information in my book, available on Amazon.
Above information based on articles by Lily Nichols – https://lilynicholsrdn.com/books/
