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TOPLINE:

Children whose mothers received 2800 IU of vitamin D3 daily from 24 weeks of gestation to 1 week postpartum showed slight improvement on memory tests at 10 years of age compared to those whose mothers received a standard dose.

METHODOLOGY:

• Researchers conducted a post hoc analysis of a randomized clinical trial of pregnant women from Denmark from 2009 to 2010, with 498 children (mean age, 10.3 years; 51.8% boys; 95.6% White) completing the prenatal vitamin D3 trial and cognitive assessments at 10 years of age.
• Pregnant women were randomly assigned to receive either high-dose vitamin D3 supplementation of 2800 IU daily or the standard-dose of 400 IU daily; 247 and 251 children were assessed in the high and standard groups, respectively.
• Cognitive functioning was assessed at 10 years of age using a neuropsychological test battery covering intelligence, processing speed, reaction time, and motor function, among others.
• Evaluation was performed using the Cambridge Neuropsychological Test Automated Battery to assess sustained attention, verbal and visual memory, and flexibility or set shift.

TAKEAWAY:

• After covariate adjustment, high-dose vitamin D3 supplementation during pregnancy was positively associated with verbal memory (beta, 0.17 SD; P = .02) and visual memory (beta, 0.24 SD; P = .01) in children at 10 years of age; mean estimated intelligence scores were 107.6 in the high-dose group compared with 107.8 in the standard-dose group.
• No significant differences were observed between the high and standard vitamin D3 groups for the remaining eight cognitive functions.
• Among individual cognitive tests, high dose was positively associated with total errors, total number recalled, and extradimensional stage errors in adjusted analyses.

IN PRACTICE:

“Our current findings at 10 years could indicate that the association of vitamin D3 supplementation with a subset of cognitive functions may become measurable later in childhood,” the authors wrote.

“[The] findings do not resolve the question of optimal vitamin D status in pregnancy, nor do they argue for abandoning the concept of sufficiency. Rather, they expose the limitations of asking that question in isolation. When nutrients function as developmental signals, their effects may be expressed not as threshold events but as subtle shifts in biological trajectory — changes that unfold over time rather than at a single concentration,” experts wrote in an invited commentary.

SOURCE:

The study was led by Olivia Frigast Frederiksen, from Herlev and Gentofte Hospital at the University of Copenhagen in Copenhagen, Denmark. It was published online on May 18, 2026, in JAMA Network Open.

LIMITATIONS:

The high preintervention level of mean 25(OH)D limited the ability to assess potential benefits for participants with low vitamin D. Including many different cognitive tests may have made it difficult to spot significant differences between groups. The small number of children with attention-deficit/hyperactivity disorder also decreased the power to detect specific associations in that subgroup.

DISCLOSURES:

The study received support from The Lundbeck Foundation, The Ministry of Health, Danish Council for Strategic Research, and The Capital Region Research Foundation, among others. Some authors disclosed receiving personal fees or grants from various sources outside the submitted work.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.