Vitamin D intake and determinants of vitamin D status during pregnancy in The Norwegian Mother, Father and Child Cohort Study.

Background: Norwegian data on vitamin D status among pregnant women indicate a moderate to high prevalence of insufficient vitamin D status (25-hydroxyvitamin D (25OHD) concentrations ≤50 nmol/L). There is a lack of population-based research on vitamin D intake and determinants of 25OHD in pregnant women from northern latitudes. The aims of this study were (1) to evaluate total vitamin D intake from both diet and supplements, (2) to investigate determinants of vitamin D status, and (3) to investigate the predicted response in vitamin D status by total vitamin D intake, in pregnant Norwegian women. Methods: In total, 2,960 pregnant women from The Norwegian Environmental Biobank, a sub-study within The Norwegian Mother, Father and Child Cohort Study (MoBa), were included. Total vitamin D intake was estimated from a food frequency questionnaire in gestational week 22. Concentrations of plasma 25OHD was analyzed by automated chemiluminescent microparticle immunoassay method in gestational week 18. Candidate determinant variables of 25OHD were chosen using stepwise backward selection and investigated using multivariable linear regression. Predicted 25OHD by total vitamin D intake, overall and stratified by season and pre-pregnancy BMI, was explored using restricted cubic splines in an adjusted linear regression. Results: Overall, about 61% of the women had a total vitamin D intake below the recommended intake. The main contributors to total vitamin D intake were vitamin D supplements, fish, and fortified margarine. Higher 25OHD concentrations were associated with (in descending order of the beta estimates) summer season, use of solarium, higher vitamin D intake from supplements, origin from high income country, lower pre-pregnancy BMI, higher age, higher vitamin D intake from foods, no smoking during pregnancy, higher education and energy intake. During October-May, a vitamin D intake according to the recommended intake was predicted to reach sufficient 25OHD concentrations >50 nmoL/L. Conclusion: The findings from this study highlight the importance of the vitamin D intake, as one of few modifiable determinants, to reach sufficient 25OHD concentrations during months when dermal synthesis of vitamin D is absent.

Atopic heredity modifies the association between maternal vitamin D status in pregnancy and the risk of atopic disease in childhood: an observational study.

BACKGROUND: The relationship between maternal vitamin D status in pregnancy and the development of atopic diseases in the offspring has been frequently studied, but with contradictory results. Previous studies have found an inverse relation between maternal vitamin D in pregnancy and the risk of atopic diseases in the child. In contrast, others have found a higher maternal 25OHD to be related to a higher risk of atopic diseases. Thus, the aim was to investigate the associations between maternal vitamin D status and intake in pregnancy with asthma, eczema and food allergies in the children up to 5 years. In addition, effect modification by reported atopic heredity was studied. METHODS: Participants in the GraviD study had 25-hydroxyvitamin D (25OHD) analyzed in serum in early (T1) and late (T3) pregnancy. Maternal dietary vitamin D intake was estimated from a short food frequency questionnaire and supplement use by questionnaires. At 5 years of age the child´s history of asthma, eczema and food allergy, including atopic heredity, was reported by questionnaire. Multivariable logistic regression was used. RESULTS: The cumulative incidence of asthma was 13%, eczema 22%, and food allergy 18%. Only among children without reported atopic heredity, maternal 25OHD of 50-75 nmol/L in T1 was associated with lower odds of asthma (OR 0.271, 95% CI 0.127-0.580), compared to maternal 25OHD > 75 nmol/L. Additionally in these children, maternal 25OHD in T3 (continuous) was associated with asthma (OR 1.014, 95% CI 1.002-1.009), and dietary vitamin D intake with eczema (OR 1.141, 95% CI 1.011-1.288). CONCLUSIONS: Among children without reported atopic heredity, higher maternal vitamin D status and intake during pregnancy was associated with increased risk of reported atopic disease.

A validated screening tool correctly identifies the majority of pregnant women at high risk of vitamin D deficiency.

BACKGROUND & AIM: The objective was to develop and validate a non-invasive screening tool to identify pregnant women at high risk of vitamin D deficiency. METHODS: Data from the Swedish prospective cohort GraviD, 2125 pregnant women, were randomly split in halves; one for developing the screening tool, and one for validation. Risk factors of vitamin D deficiency (serum 25-hydroxyvitamin D < 30 nmol/L) were identified using logistic regression analyses and odds ratios were translated into scores. Cutt offs to indicate high risk of vitamin D deficiency were evaluated by receiver operator characteristics. RESULTS: Five variables (season, clothing, eye color, fortified milk intake and vitamin D supplement use) were included in the screening tool. The possible total score was 0-42. Mean (95% CI) area under the curve for classification of vitamin D deficiency was 0.921 (0.893-0.948) (p < 0.001). A score of ≥15 points had 92% sensitivity and 76% specificity to identify women with 25OHD <30 nmol/L. This cut off had a positive predictive value of 31% and a negative predictive value of 99%. CONCLUSION: This short non-invasive screening tool is valid as it correctly identified the majority of the vitamin D deficient pregnant women, who may benefit from further investigation for definite diagnosis and subsequent treatment.