Does a mother's vitamin D level during pregnancy shape how her child develops? Researchers analysed 252 mother-child pairs from the APrON cohort (a group of families followed over time). They measured vitamin D in mums' blood in the second trimester, then assessed the children at 3–5 years on cognitive (thinking), language, motor (movement) and behavioural outcomes.
The findings were published in Frontiers in Pediatrics. Here is what they do and do not tell us.
Thinking, language and behaviour: no link found
The researchers found no association between mums' vitamin D levels and children's cognitive, language or behavioural outcomes. In this group, a higher or lower vitamin D level in pregnancy did not line up with how the children did in these areas by preschool age.
Motor skills: a small hint that did not survive a stricter test
Motor outcomes were the one exception. Higher maternal vitamin D was linked with slightly better motor scores (B = 0.04, p = 0.03). This was a very small difference.
The researchers tested many outcomes at once, and the more things you test, the more likely one looks positive by chance. When they adjusted for this (called correction for multiple comparisons), the motor result no longer counted as solid (q = 0.18).
The link also weakened when mums were split into four equal groups by vitamin D level, and when "sufficient" was defined as 30 ng/mL. Using a 20 ng/mL cut-off for "sufficient", children's outcomes did not differ. So the authors call this only "preliminary evidence".
Baby's "biological age" did not explain anything, but the check was small
The team also asked whether vitamin D might work through epigenetic age acceleration (EAA). This is a measure, read from chemical tags on DNA, of whether the body looks biologically older or younger than its calendar age. In 130 children, cheek-cell samples taken at 3 months were used to estimate it.
They found no sign that EAA linked vitamin D to motor skills. However, with only 130 children, small effects could have been missed.
What we can and cannot conclude
- This type of study shows associations only. It cannot prove that vitamin D caused any difference in children.
- Vitamin D was measured once, in the second trimester, in one form (25(OH)D3).
- The study did not look at Singapore or other Asian families, so we cannot say whether the results apply locally.
- The study did not test whether taking vitamin D supplements changes children's development.
The honest takeaway is a modest one. In this group, mums' second-trimester vitamin D did not predict their children's thinking, language or behaviour at 3–5 years. The motor-skills hint is too weak to act on. The authors say further work should look at different forms of vitamin D and at different ways of defining "sufficient" levels. Any questions about vitamin D in pregnancy are best taken to your own doctor.