The conclusion of this study pretty much says it all. If a mother is deficient in vitamin D during certain points of the pregnancy, the child has a much greater chance (almost 2x) of having language impairments at 5 and 10 years of age.
The abstract is below.
Maternal Serum Vitamin D Levels During Pregnancy and Offspring Neurocognitive Development
OBJECTIVE: To determine the association between maternal serum 25(OH)-vitamin D concentrations during a critical window of fetal neurodevelopment and behavioral, emotional, and language outcomes of offspring.
METHODS: Serum 25(OH)-vitamin D concentrations of 743 Caucasian women in Perth, Western Australia (32°S) were measured at 18 weeks pregnancy and grouped into quartiles. Offspring behavior was measured with the Child Behavior Checklist at 2, 5, 8, 10, 14, and 17 years of age (n range = 412–652). Receptive language was assessed with the Peabody Picture Vocabulary Test—Revised at ages 5 (n = 534) and 10 (n = 474) years. Raw scores were converted to standardized scores, incorporating cutoffs for clinically significant levels of difficulty.
RESULTS: X2 analyses revealed no significant associations between maternal 25(OH)-vitamin D serum quartiles and offspring behavioral/emotional problems at any age. In contrast, there were significant linear trends between quartiles of maternal vitamin D levels and language impairment at 5 and 10 years of age. Multivariate regression analyses, incorporating a range of confounding variables, found that the risk of women with vitamin D insufficiency (=46 nmol/L) during pregnancy having a child with clinically significant language difficulties was increased close to twofold compared with women with vitamin D levels > 70 nmol/L.
CONCLUSIONS: Maternal vitamin D insufficiency during pregnancy is significantly associated with offspring language impairment. Maternal vitamin D supplementation during pregnancy may reduce the risk of developmental language difficulties among their children.
Whitehouse AJ, Holt BJ, Serralha M, Holt PG, Kusel MM, Hart PH. Maternal serum vitamin d levels during pregnancy and offspring neurocognitive development. Pediatrics. 2012 Mar;129(3):485-93. Epub 2012 Feb 13. PubMed PMID: 22331333 DOI: 10.1542/peds.2011-2644