Can Higher Dose Vitamin D During Pregnancy Support a Child’s Memory?

TLDR

A 2026 analysis of a randomized clinical trial followed nearly 500 children to age 10 and found that mothers assigned to a higher dose of vitamin D3 during late pregnancy had children who performed modestly better on verbal memory and visual memory tests than children whose mothers received the standard dose.

The higher dose group received a total of 2,800 IU of vitamin D3 per day, compared with 400 IU per day in the standard dose group, beginning at pregnancy week 24 and continuing until one week after birth. The study does not prove that all pregnant women should take 2,800 IU per day, and the authors emphasize that the analysis was conducted after the original trial and involved a population that was generally not vitamin D deficient.

Can Vitamin D During Pregnancy Influence a Child’s Brain Development?

Vitamin D is usually associated with bones.

That makes sense. It plays an essential role in calcium metabolism and skeletal development.

But vitamin D also appears to have important functions in the developing brain.

During pregnancy, vitamin D is involved in processes including neuronal development, neurotransmitter production, calcium signaling, and antioxidant activity. Vitamin D receptors and the enzymes needed to activate vitamin D are also present in the human brain.

That has led researchers to ask a fascinating question:

Could a mother’s vitamin D intake during pregnancy influence how her child’s brain functions years later?

A new study published in JAMA Network Open provides one of the most interesting answers yet.

Researchers followed children whose mothers had previously participated in a randomized vitamin D trial during pregnancy and tested their cognitive performance approximately 10 years later.

The results suggest that higher dose vitamin D supplementation during late pregnancy may be associated with modest improvements in specific types of memory.

Why Study Vitamin D and the Developing Brain?

Brain development begins long before birth.

During pregnancy, billions of neurons are forming, migrating, connecting, and organizing into increasingly complex networks.

Nutrition can influence that process.

The study authors note that vitamin D may play a role in:

• Neuronal differentiation
• Neurotransmitter synthesis
• Intracellular calcium signaling
• Antioxidant activity
• Overall neurodevelopment

Observational research has also linked lower prenatal vitamin D status with several neurodevelopmental outcomes, although those associations have not always been consistent.

The important limitation of observational studies is that they cannot prove cause and effect.

Women with higher vitamin D levels may differ in many other ways, including diet, physical activity, socioeconomic status, sun exposure, or overall health.

That is why randomized trials are particularly valuable.

The Original Vitamin D Trial

The research came from the Copenhagen Prospective Studies on Asthma in Childhood cohort in Denmark.

In the original trial, 623 pregnant women were randomized beginning at approximately pregnancy week 24.

One group received:

2,400 IU of supplemental vitamin D3 plus the standard 400 IU per day

for a total of:

2,800 IU per day.

The comparison group received:

400 IU per day.

Supplementation continued from pregnancy week 24 until one week after delivery.

The original study was not designed primarily to test cognition. Its main purpose was to investigate respiratory outcomes in the children.

Years later, researchers returned to the cohort to ask whether prenatal vitamin D exposure was associated with cognitive performance at age 10.

Nearly 500 Children Were Tested at Age 10

A total of 498 children completed both the prenatal vitamin D trial and the later cognitive assessment.

Their average age was approximately 10.3 years.

Of those children:

247 had been exposed prenatally to the higher vitamin D dose

and

251 had been exposed to the standard dose.

The researchers did not rely on a simple questionnaire or school grades.

Children completed an extensive neuropsychological testing battery covering eight broad cognitive domains and 11 specific cognitive functions.

Researchers tested:

• Intelligence
• Processing speed
• Reaction time
• Sustained attention
• Motor speed
• Verbal memory
• Visual memory
• Verbal working memory
• Cognitive flexibility
• Spatial working memory
• Planning

That comprehensive testing is one of the strengths of the study.

The Biggest Finding: Better Visual Memory

The clearest benefit appeared in visual memory.

Children whose mothers received the higher vitamin D dose performed approximately:

0.24 standard deviations better on visual memory testing

than children in the standard dose group.

The 95 percent confidence interval ranged from 0.06 to 0.42 standard deviations, and the result remained statistically significant after adjustment for multiple comparisons.

Visual memory refers to your ability to remember visual information such as shapes, locations, patterns, and spatial relationships.

The test used in this study asked children to learn and recall associations between visual patterns and locations.

The effect was not huge, but it was measurable a decade after the prenatal intervention.

That is what makes the finding especially interesting.

Verbal Memory Improved Too

Researchers also found an improvement in verbal memory.

The higher dose group scored approximately:

0.17 standard deviations higher

on verbal memory testing.

The confidence interval ranged from 0.03 to 0.32 standard deviations, and this result also survived correction for multiple testing.

Verbal memory involves learning and recalling information presented through words.

In this study, the children completed tests requiring them to remember words and objects over repeated learning trials.

Again, this was a modest effect.

But the fact that both verbal and visual memory moved in the same favorable direction strengthens the possibility that prenatal vitamin D exposure may influence certain aspects of memory development.

What About Executive Function?

Initially, the researchers also found a positive association with flexibility or set shifting.

This is an executive function involving the ability to change strategies or shift attention when the rules of a task change.

The higher dose group scored approximately 0.19 standard deviations better before correction for multiple testing.

However, this result did not remain statistically significant after false discovery rate correction.

That matters.

When researchers test many different outcomes, some can appear significant purely by chance.

Multiple comparison corrections make the statistical threshold more difficult to reach.

After that correction, the strongest evidence remained for:

Verbal memory

and

Visual memory.

The executive function result should therefore be viewed as suggestive rather than confirmed.

Vitamin D Did Not Improve Every Type of Cognition

Another important point is what the study did not find.

There were no significant differences between groups in:

• Estimated intelligence
• Processing speed
• Reaction time
• Sustained attention
• Motor speed
• Verbal working memory
• Spatial working memory
• Planning

Estimated intelligence scores were nearly identical:

107.6 in the higher dose group

versus

107.8 in the standard dose group.

So this was not a case where higher prenatal vitamin D appeared to make children universally “smarter.”

The effect was much more specific.

Memory appeared to benefit. Most other cognitive functions did not.

That distinction is critical when translating the research into practical recommendations.

The Vitamin D Supplement Actually Changed Vitamin D Status

The intervention produced a meaningful difference in maternal vitamin D levels.

Before supplementation, median maternal 25 hydroxyvitamin D was about 30.3 ng/mL.

After the intervention, median concentrations were:

41.9 ng/mL in the higher dose group

versus

27.5 ng/mL in the standard dose group.

More than half of the higher dose group reached serum concentrations of at least 40 ng/mL, compared with only about 17 percent of the standard dose group.

That confirms that the supplement meaningfully changed maternal vitamin D status rather than simply assigning women to different pill bottles.

Did the Child’s Later Vitamin D Status Explain the Results?

Interestingly, no.

Researchers examined whether the children's vitamin D concentrations at six months or six years altered the relationship between prenatal supplementation and cognition.

They did not find significant interactions.

That suggests the memory findings may be associated specifically with prenatal exposure, rather than simply reflecting children who continued to maintain higher vitamin D levels throughout childhood.

The authors suggest pregnancy may represent an important developmental window.

The latter half of pregnancy involves rapid maturation of the cerebral cortex, which could potentially make the developing brain particularly sensitive to vitamin D availability.

That remains a hypothesis rather than something this trial directly proved.

What About Children With ADHD?

Researchers also investigated whether ADHD diagnosis influenced the findings.

Among children without ADHD, the association remained significant for:

Verbal memory: 0.18 standard deviations better

and

Visual memory: 0.28 standard deviations better.

However, the statistical interaction with ADHD status itself was not significant.

That means researchers cannot conclude that vitamin D works differently in children with or without ADHD.

The study also contained relatively few children with ADHD or autism, making these subgroup analyses much less reliable.

This study therefore should not be interpreted as evidence that prenatal vitamin D prevents or treats ADHD or autism.

Were Women in the Study Vitamin D Deficient?

For the most part, no.

This is one of the most important details in the paper.

Median maternal vitamin D levels before treatment were approximately 30.3 ng/mL, and only about 15 percent of participants had concentrations below 20 ng/mL.

In other words, this was not primarily a vitamin D deficient population.

That creates an interesting possibility.

The effect could potentially be larger in women with inadequate vitamin D status, because they have more room to benefit.

But the opposite is also possible.

We simply do not know from this trial.

The researchers specifically state that the relatively high baseline vitamin D status limited their ability to determine how higher dose supplementation might affect vitamin D deficient pregnancies.

Why Might Vitamin D Affect Memory?

The study was not designed to identify a mechanism, so we should be careful here.

But several biological possibilities are discussed.

Vitamin D is involved in fetal brain processes including neuronal differentiation, neurotransmitter production, calcium signaling, and antioxidant protection.

The authors also point out that different brain regions develop at different times during pregnancy.

Because this intervention began at week 24, the exposure largely occurred during the third trimester, a period of rapid cortical development.

That could potentially explain why supplementation affected certain cognitive functions rather than intelligence or cognition as a whole.

But that interpretation remains theoretical.

An Earlier Assessment Found No Cognitive Benefit

There is another fascinating part of this study.

Researchers previously assessed children from this same trial at approximately 2.5 years old and found no significant cognitive benefit.

The differences appeared when the children were tested again at age 10.

Why?

One possibility proposed by the authors is that certain cognitive functions become more refined and measurable later in childhood.

A toddler's cognitive assessment may simply not capture subtle differences in memory or executive functioning that become more obvious during the school years.

This is one reason long term follow up studies are so valuable.

Some effects of prenatal nutrition may take years to become apparent.

Does This Mean Pregnant Women Should Take 2,800 IU of Vitamin D?

This study alone cannot make that recommendation.

That is particularly important because supplementation during pregnancy is a medical decision.

The trial compared 2,800 IU per day with 400 IU per day, beginning relatively late in pregnancy.

It did not compare 2,800 IU with no vitamin D at all.

It also does not establish that 2,800 IU is the ideal dose.

Nor does it show that taking more would produce greater benefits.

Pregnant women should discuss vitamin D intake, prenatal supplements, blood testing, and appropriate dosing with their obstetrician or other qualified healthcare professional.

The important takeaway is not:

“Every pregnant woman needs 2,800 IU.”

It is:

The amount of vitamin D consumed during pregnancy may matter for certain aspects of a child's long term cognitive development, and this deserves more research.

Important Limitations

This is an intriguing study, but there are several important limitations.

First, the cognitive analysis was post hoc.

That means cognitive performance at age 10 was not a prespecified primary outcome when the original randomized trial was designed.

Post hoc analyses carry a greater risk of chance findings.

Second, researchers evaluated 11 different cognitive functions.

Although they appropriately corrected for multiple testing, the more outcomes researchers examine, the greater the possibility of random associations.

Third, most mothers were already relatively vitamin D sufficient.

Only 15 percent had levels below 20 ng/mL before supplementation.

Fourth, supplementation began at pregnancy week 24, so the study tells us very little about whether vitamin D intake during the first or second trimester might influence cognition differently.

Fifth, the cohort was overwhelmingly White, limiting our ability to know whether the findings apply equally across diverse populations.

And finally, cognition was measured at one point in time at age 10 rather than repeatedly across childhood.

These limitations mean the results should be viewed as promising rather than definitive.

The Bottom Line

This study offers an intriguing glimpse into how nutrition during pregnancy may influence a child many years later.

Pregnant women randomized to 2,800 IU of vitamin D3 per day from week 24 through one week after delivery had children who performed modestly better on tests of verbal and visual memory at age 10 than women receiving 400 IU per day.

The study did not show better overall intelligence, attention, processing speed, working memory, or planning.

That makes the conclusion more specific and more interesting.

Rather than broadly “boosting brain development,” higher prenatal vitamin D exposure may influence particular aspects of memory.

Because the analysis was post hoc and the study population was largely vitamin D sufficient, additional randomized trials are needed before changing prenatal vitamin D recommendations.

Still, the findings reinforce a larger lesson:

Nutrition during pregnancy may have effects that extend far beyond birth, potentially influencing how the brain develops and functions years later.

References

1. Frederiksen OF, Jepsen JRM, Brustad N, et al. High Dose Vitamin D3 Supplementation During Pregnancy and Test Based Cognitive Performance at Age 10 Years: A Post Hoc Secondary Analysis of a Randomized Clinical Trial. JAMA Network Open. 2026;9(5):e2611464. doi:10.1001/jamanetworkopen.2026.11464.
2. Eyles DW. Vitamin D: brain and behavior. JBMR Plus. 2020;5(1):e10419.
3. Eyles D, Burne T, McGrath J. Vitamin D in fetal brain development. Seminars in Cell & Developmental Biology. 2011;22(6):629 to 636.
4. Saraf R, Morton SMB, Camargo CA Jr, Grant CC. Global summary of maternal and newborn vitamin D status: a systematic review. Maternal & Child Nutrition. 2016;12(4):647 to 668.

Frequently Asked Questions

How much vitamin D did the pregnant women take?

The higher dose group received 2,400 IU of study vitamin D3 plus the standard 400 IU, for a total of 2,800 IU per day. The comparison group received 400 IU per day. Supplementation began at week 24 of pregnancy and continued until one week after delivery.

Did higher dose vitamin D increase the children’s IQ?

No. Estimated intelligence scores were virtually identical between the groups. The benefits were specific to verbal and visual memory rather than overall intelligence.

Which cognitive abilities improved?

After correcting for multiple testing, verbal memory and visual memory remained significantly better in the higher dose group. An initial improvement in cognitive flexibility did not remain statistically significant after correction.

Should pregnant women take 2,800 IU of vitamin D?

This study alone cannot establish an optimal prenatal vitamin D dose. Supplement requirements during pregnancy should be individualized with a healthcare professional, particularly when considering doses beyond what is already provided by a prenatal vitamin.

Were the mothers vitamin D deficient?

Most were not. Median vitamin D levels were about 30.3 ng/mL before supplementation, and approximately 15 percent had levels below 20 ng/mL. That limits the ability to determine whether women with vitamin D deficiency would experience greater benefits.