A new study published in PLOS One has found that low maternal vitamin D levels during late pregnancy may lead to impaired language development in infants.
As many readers of our site know, vitamin D status during pregnancy strongly relates to the vitamin D status of infants at birth. Increasing amounts of research shows that this strong association relates to various health outcomes at birth.
Recent research, for example, shows low vitamin D levels during pregnancy may increase the risk for tooth decay in children. Furthermore, it has been suggested that low maternal vitamin D status relates to impaired brain and motor development in infants.
Considering the complexity of the relationship between a mother’s health and lifestyle during pregnancy and the infant’s growth and development, there is a need for more research to be done to fully understand the role that vitamin D plays in the mother-infant relationship.
Recently, Dr. Sarah Hanieh and colleagues conducted a prospective cohort study to evaluate the vitamin D status of pregnant women and determine how vitamin D status affects various birth outcomes.
The research team recruited 960 pregnant women and followed them through birth. The women were recruited from a rural region in Vietnam, which sits at a latitude of 20.2 degrees and is thus an area of abundant sun exposure that allows for adequate vitamin D production.
The researchers measured the expectant mothers’ vitamin D levels at 32 weeks pregnant as well as collected information on their occupation, education, and pregnancy history.
At birth, the researchers collected data on various birth outcomes. These outcomes included whether the baby was born preterm or was small for gestational age.
Finally, the researchers measured the infants’ vitamin D levels and their physical and mental development at 6 months of age. For mental development, the researchers analyzed the infants’ cognition, motor skills, social and emotional skills, and language skills by using the Bayley Scales of Infant Development, 3rd Edition (BSID III).
BSID III is a standard test used to measure motor, language and cognitive development in infants and toddlers. The test consists of assigned play tasks in which results are compiled into a score with the higher score signifying better motor, language and cognitive skills.
The researchers wanted to know if higher vitamin D status during late pregnancy would be associated with better physical growth and BSID III scores in the mothers’ children.
Here is what the researchers found:
- Overall, 60% of the women had vitamin D levels lower than 30 ng/ml.
- There was a non-significant trend towards a reduced risk of preterm birth in mothers with higher vitamin D levels.
- Head circumference was measured in 49.5% of infants, and higher vitamin D levels were associated with lower head circumference, although this association did not persist at 6 months of age.
- There was an inverse relationship between maternal vitamin D status and infant length-to-age ratio.
- Babies born to mothers with vitamin D levels lower than 15 ng/ml had lower language scores compared to babies born to mothers with vitamin D levels of 30 ng/ml or higher.
- There were no relationships between maternal vitamin D status and any of the other BSID III development scores.
The researchers concluded,
“These results indicate that there is a high prevalence of vitamin D insufficiency in pregnant women residing in rural Ha Nam Province, Vietnam. Our findings show that low vitamin D levels in late pregnancy (<15 ng/ml) are associated with reduced infant language development at six months of age.”
Commenting on the effects of vitamin D status on language development, the researchers stated,
“Our finding of an association between maternal vitamin D and infant language composite scores, that was only observed when maternal vitamin D levels fell below 15 ng/ml in late pregnancy, raises the possibility that there is a threshold effect, and that language impairment is a feature of more marked vitamin D deficiency.”
These results were found in a very specific population of pregnant women and infants in a rapidly developing rural area of Vietnam, meaning that these results cannot be generalized to other populations.
The results of this study adds to the increasing amount of evidence that vitamin D status during pregnancy affects the cognitive development of infants. At the same time, it demonstrates how more research is needed to fully understand the role of adequate maternal vitamin D levels throughout pregnancy in infant growth and development.
It also illustrates the high prevalence of vitamin D deficiency in a region of abundant sunlight, highlighting the increasing importance that lifestyle and urban development have on vitamin D status.
Future trials are needed in which vitamin D supplements are administered to deficient women during different stages of pregnancy. This will help determine how correcting for vitamin D deficiency impacts the physical and mental development of their babies.