Vitamin D during pregnancy and maternal, neonatal and infant health outcomes: a systematic review and meta-analysis

Non-skeletal health effects of vitamin D supplementation: A systematic review on findings from meta-analyses summarizing trial data

BACKGROUND

A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D (25OHD) levels on non-skeletal outcomes. We performed a systematic quantitative review on characteristics of randomized clinical trials (RCTs) included in meta-analyses (MAs) on non-skeletal effects of vitamin D supplementation.

METHODS AND FINDINGS

We identified systematic reviews (SR) reporting summary data in terms of MAs of RCTs on selected non-skeletal outcomes. For each outcome, we summarized the results from available SRs and scrutinized included RCTs for a number of predefined characteristics. We identified 54 SRs including data from 210 RCTs. Most MAs as well as the individual RCTs reported null-findings on risk of cardiovascular diseases, type 2 diabetes, weight-loss, and malignant diseases. Beneficial effects of vitamin D supplementation was reported in 1 of 4 MAs on depression, 2 of 9 MAs on blood pressure, 3 of 7 MAs on respiratory tract infections, and 8 of 12 MAs on mortality. Most RCTs have primarily been performed to determine skeletal outcomes, whereas non-skeletal effects have been assessed as secondary outcomes. Only one-third of the RCTs had low level of 25OHD as a criterion for inclusion and a mean baseline 25OHD level below 50 nmol/L was only present in less than half of the analyses.

CONCLUSIONS

Published RCTs have mostly been performed in populations without low 25OHD levels. The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels.

Vitamin D in pregnancy: current perspectives and future directions

As neonatal vitamin D status is determined by circulating maternal 25-hydroxyvitamin D [25(OH)D] concentrations, prevention of maternal vitamin D deficiency during pregnancy is essential for the avoidance of neonatal deficiency. However, a high prevalence of vitamin D deficiency has been extensively reported among gravidae and neonates from ethnic minorities and white populations resident at high latitude. Currently, regulatory authorities recommend vitamin D intakes for pregnant women that are similar to non-pregnant adults of the same age, at 10-15 µg/day (400-600 IU), to meet 25(OH)D thresholds of 25-50 nmol/liter. The lack of pregnancy-specific dietary recommendations is due to inadequate data indicating whether nutritional requirements for vitamin D during pregnancy differ from the non-pregnant state. In addition, there are few dose-response studies to determine the maternal 25(OH)D response to vitamin D intake throughout pregnancy at high latitude. These data are also required to determine vitamin D requirements during pregnancy for prevention of neonatal deficiency, an outcome which is likely to require a higher maternal 25(OH)D concentration than prevention of maternal deficiency only. With regard to the impact of vitamin D on perinatal health outcomes, which could guide pregnancy-specific 25(OH)D thresholds, dietary intervention studies to date have been inconsistent and recent systematic reviews have highlighted issues of low quality and a high risk of bias as drawbacks in the trial evidence to date. Many observational studies have been hampered by a reliance on retrospective data, unclear reporting, suboptimal clinical phenotyping and incomplete subject characterization. Current investigations of vitamin D metabolism during pregnancy have potentially exciting implications for clinical research. This paper provides an update of current dietary recommendations for vitamin D in pregnant women and a synopsis of the evidence relating vitamin D status with maternal and infant health.

Vitamin D levels during pregnancy and associations with birth weight and body composition of the newborn: a longitudinal multiethnic population-based study

We investigated associations between serum 25-hydroxyvitamin D (25(OH)D) in pregnancy and birth weight and other neonatal anthropometric measures. The present study was a population-based, multiethnic cohort study of 719 pregnant women (59 % ethnic minorities) in Oslo, Norway, delivering a singleton neonate at term and with birth weight measurements. In a representative sample, anthropometric measurements were taken. Maternal 25(OH)D was measured at gestational weeks 15 and 28. Women with 25(OH)D <37 nmol/l were recommended vitamin D3 supplementation. Separate linear regression analyses were performed to model the associations between 25(OH)D and each of the outcomes: birth weight, crown-heel length, head circumference, abdominal circumference, sum of skinfolds, mid-upper arm circumference and ponderal index. In early pregnancy, 51 % of the women were vitamin D deficient (25(OH)D<50 nmol/l). In univariate analyses and in models adjusting for maternal age, parity, education, prepregnancy BMI, season, gestational age and neonate sex, maternal 25(OH)D was significantly associated with birth weight, head circumference, abdominal circumference and ponderal index (P<0·05 for all), when used as a continuous variable and categorised (consistently low, consistently high, increasing and decreasing level). However, after adjusting for ethnicity, 25(OH)D was no longer associated with any of the outcomes. Sex-specific associations for abdominal circumference and sum of skinfolds were found (P for interaction<0·05). In conclusion, in a multiethnic cohort of pregnant women with high prevalence of vitamin D deficiency, we found no independent relation between maternal vitamin D levels and any of the neonatal anthropometric measures, and the strong association between ethnicity and neonatal outcomes was not affected by maternal vitamin D status.

Vitamin D status and the prevalence of deficiency in lactating women from eight provinces and municipalities in China

BACKGROUND

Vitamin D deficiency has become prevalent worldwide in recent years. However, less evidence was available for lactating women.

OBJECTIVE

The purpose of the study was to understand vitamin D status and prevalence of deficiency in lactating women and associated risk factors for vitamin D deficiency from eight provinces and municipalities in China.

METHODS

Lactating women within 1-10 months postpartum were recruited in 2011-2013 from eight provinces and municipalities in China. Radioimmunoassay was used to measure serum 25-hydroxyvitamin D [25(OH)D] concentration. Standardized questionnaire was used to collect information on season, living site, ethnicity and socio-demographic characteristics.

RESULTS

Totally 2004 lactating women were recruited. The median (p25, p75) of 25(OH)D was 15.8 (10.5, 24.0) nmol/L. The prevalence of vitamin D deficiency was 85.3% as 25(OH)D <30nmol/L. Serum 25(OH)D levels of lactating women were significantly lower during October-January (14.0nmol/L) than during February-May (18.0nmol/L) (P<0.001), and were significantly higher in Dai ethnicity (22.5nmol/L) than in Hui ethnicity (Chinese Muslims) (9.0nmol/L) (P<0.001). For every 10,000 CNY annual income per capita increasing, serum 25(OH)D levels significantly increased 1.04 times (P<0.001). The odds of vitamin D deficiency in winter were 2.56 times higher than that in spring (OR 2.56, 95%CI: 1.91-3.43).

CONCLUSIONS

Vitamin D deficiency of lactating women was highly prevalent in the eight provinces and municipalities in China. It is urgent to study the strategy and intervention ways for improving vitamin D status of lactating women, especially for certain population groups during low sunlight exposure season.

Maternal vitamin D insufficiency and risk of adverse pregnancy and birth outcomes: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Three previous reviews on the association of vitamin D insufficiency in pregnancy with preterm birth (PTB) and stillbirth were limited in scope and deemed inconclusive. With important new evidence accumulating, there is the need to update the previous estimates and assess evidence on other clinically important outcomes such as spontaneous abortion and Apgar score. We conducted a systematic review and meta-analysis to evaluate the quality and strength of the available evidence on the relations between vitamin D nutritional status, and pregnancy and birth outcomes.

METHODS

PubMed and Scopus databases were searched from their inception to June, 2015 with no language restrictions imposed. Eighteen longitudinal studies satisfied the inclusion criteria. Random effects model was applied in computing the summary effect estimates and their corresponding 95% confidence intervals.

RESULTS

Serum 25(OH)D levels <75 nmol/l was associated with 83% (95% CI: 1.23, 2.74) and 13% (95% CI: 0.94, 1.36) increased risk of PTB measured at <32-34 weeks and <35-37 weeks, respectively. An inverse dose-response relation was observed for both PTB outcome. Serum 25(OH)D levels <75 nmol/l was also associated with 11% increased risk of spontaneous PTB (<35-37 weeks; RR = 1.11; 95% CI: 0.75, 1.65) with a dose-response relation also noted. Vitamin D insufficiency was not associated with risk of spontaneous abortion and stillbirth (RR of 1.04 [95% CI: 0.95, 1.13] and 1.02 [95% CI: 0.96, 1.09], respectively), as well as short gestational length (ES = -0.24, 95% CI: -0.69, 0.22), and low Apgar score.

CONCLUSIONS

We found vitamin D insufficiency to be associated with risk of PTB. Regarding spontaneous abortion and stillbirth, the available evidence suggest no association with low vitamin D levels. The evidence on vitamin D nutrition and Apgar score is conflicting and controversial. Overall, the experimental evidence uncovered was small and weak. Hence, the benefits of vitamin D supplementation during pregnancy should be further evaluated through rigorous intervention studies.

Does involvement in a cohort study improve health and affect health inequalities? A natural experiment

BACKGROUND

Evidence suggests that the process of taking part in health research can improve participants' health, independent of any intended intervention. However, no research has yet explored whether these effects differ across socioeconomic groups. If the effect of mere participation in health research also has a social gradient this could increase health inequalities and bias research results. This study used the Born in Bradford family cohort (BIB) to explore whether simply taking part in BIB had improved participants' health and, if so, whether this effect was mediated by socioeconomic status.

METHODS

Survey data on self-reported health behaviours were collected between 2007 and 2010 as part of BIB. These were augmented by clinical data on birth weight. Pregnant women on their second pregnancy, joining BIB for the first time formed the control group. Their health was compared to women on their second pregnancy who had both pregnancies within the study, who formed the exposed group. In order to limit the inherent bias in a non-randomised study, propensity score analysis was used, matching on age, ethnicity, education and date of questionnaire. The results were then compared according to mothers' education.

RESULTS

Of six outcomes tested, only alcohol consumption showed a statistically significant reduction with exposure to BIB (OR: 0.35, 95% CIs 0.13, 0.92). Although effect estimates were larger for women with higher education compared to lower education, these effects were not statistically significant.

CONCLUSIONS

Despite one significant finding, these results overall are insufficient to conclude that simply taking part in BIB affected participants' health. We recommend that socioeconomic status is considered in future studies testing effects of research participation, and that randomised studies with larger sample sizes are conducted.

Extremely High Prevalence of Maternal and Neonatal Vitamin D Deficiency in the Arab Population

BACKGROUND

Vitamin D deficiency is a global public health problem. The published literature on vitamin D deficiency is limited among Arab pregnant women and its association with different metabolic markers.

OBJECTIVE

To determine the prevalence of vitamin D deficiency in Arab pregnant women and neonates and its association with various biomarker profiles.

METHODS

This is a multicenter study taken from a large prospective project in Riyadh, the capital city of Saudi Arabia. Maternal biochemical levels were measured routinely. Maternal and neonatal 25(OH)D levels were assessed using a chemiluminescence immunoassay. A total of 1,097 pregnant women >16 years old with gestational ages <24 weeks were recruited from different tertiary hospitals in Riyadh between February 2011 and June 2012.

RESULTS

Almost 85% of pregnant subjects had 25(OH)D level <50 nmol/L. Vitamin D deficiency among neonates was 88%. Maternal 25(OH)D was significantly associated with neonatal 25(OH)D (r = 0.54, p < 0.01), as well as serum calcium (r = 0.16, p = 0.02) and phosphate levels (r = 0.17, p = 0.02), and had an inverse correlation with parathyroid hormone (r = -0.22, p = 0.001).

CONCLUSION

Maternal and neonatal vitamin D deficiency is alarmingly high in Arabs and significantly associated with each another. Universal screening for serum 25(OH)D may be appropriate for Arab mothers and vitamin D supplementation mandatory until term. The study puts a spotlight on vitamin D deficiency with the hope that health professionals will address it adequately to prevent the known long-term consequences for metabolism and bone health of both mothers and their children.

Low Prevalence of Vitamin D Insufficiency among Nepalese Infants Despite High Prevalence of Vitamin D Insufficiency among Their Mothers

Background: Describing vitamin D status and its predictors in various populations is important in order to target public health measures. Objectives: To describe the status and predictors of vitamin D status in healthy Nepalese mothers and infants. Methods: 500 randomly selected Nepalese mother and infant pairs were included in a cross-sectional study. Plasma 25(OH)D concentrations were measured by LC-MS/MS and multiple linear regression analyses were used to identify predictors of vitamin D status. Results: Among the infants, the prevalence of vitamin D insufficiency (25(OH)D <50 nmol/L) and deficiency (<30 nmol/L) were 3.6% and 0.6%, respectively, in contrast to 59.8% and 14.0% among their mothers. Infant 25(OH)D concentrations were negatively associated with infant age and positively associated with maternal vitamin D status and body mass index (BMI), explaining 22% of the variability in 25(OH)D concentration. Global solar radiation, maternal age and BMI predicted maternal 25(OH)D concentration, explaining 9.7% of its variability. Conclusion: Age and maternal vitamin D status are the main predictors of vitamin D status in infants in Bhaktapur, Nepal, who have adequate vitamin D status despite poor vitamin D status in their mothers.

Prevalence and predictors of vitamin D deficiency based on maternal mid-gestation and neonatal cord bloods: The Generation R Study

BACKGROUND

Population-based studies have confirmed that the prevalence of vitamin D deficiency is substantial in many societies, and is of particular concern in pregnant women. Vitamin D deficiency during pregnancy is associated with a wide range of adverse maternal and offspring health outcomes. To date, studies of vitamin D deficiency during pregnancy have focused on measurements at one or two time points in isolation. We examined both midgestation and cord blood 25 hydroxyvitamin D (25OHD) concentration and explored the prevalence and correlates of vitamin D deficiency in a large ethnically diverse cohort of pregnant women and their infants in the Netherlands.

METHODS

This study was embedded in the Generation R Study, a population-based prospective cohort from fetal life onwards in Rotterdam, The Netherlands. Using a highly sensitive tandem mass spectroscopy-based assay, we measured 25OHD in 7256 midgestation samples (mean gestation 20.6 weeks) and 5023 neonatal cord blood samples (mean gestation 40.0 weeks). Using a conservative threshold of less than 25nmol/L to define vitamin D deficiency, we examined the prevalence and socio-demographic correlates of vitamin D deficiency in mothers and infants. We also derived a measure of vitamin D deficiency based on the two time points in order to explore persistent vitamin D deficiency in mother-infant pairs.

RESULTS

The prevalence of vitamin D deficiency at midgestation was 26%, while in neonates 46% were deficient. 21% of the mother-infant pairs had persistent vitamin D deficiency (i.e., deficient in maternal and cord samples) and an additional 29% were vitamin D deficient in one of the two samples only. Persistent vitamin D deficiency was strongly associated with non-European ancestry and spring birth.

CONCLUSIONS

A sizeable proportion of women and their neonatal offspring in the Generation R cohort were vitamin D deficient. In light of the large body of evidence linking vitamin D deficiency with adverse health outcomes for pregnant women and their offspring, our findings indicate a large unmet need in this population. In particular, women and infants from non-European ethnic background are at high risk of vitamin D deficiency.

Maternal Vitamin D Status at Week 30 of Gestation and Offspring Cardio-Metabolic Health at 20 Years: A Prospective Cohort Study over Two Decades

Background/Objectives

Vitamin D deficiency is common among pregnant women and since the fetus relies exclusively on maternal supply, deficiency could potentially interfere with fetal development. Vitamin D blood concentrations during pregnancy have been associated with offspring cardio-metabolic health in a few previous studies but the evidence is still inconsistent and only one previous study has followed the offspring into adulthood. The aim of the present study was to investigate the association between maternal serum concentration of vitamin D (25(OH)D) in week 30 of gestation and offspring cardio-metabolic risk factors at 20 years.

Subjects/Methods

A follow up study of a Danish birth cohort from 1988–89 (n = 965) was conducted. A blood sample was drawn from the women in week 30 of gestation. In 2008–2009, 95% of the original mother and child dyads could be identified in the central registration registry and were alive and living in Denmark. The offspring were followed up with self-reported anthropometrics (N = 629, 69%) and a clinical examination (N = 410, 45%). Multiple linear regression was used to estimate the association between maternal 25(OH)D and offspring cardio-metabolic risk factors adjusting for potential confounders.

Results

No overall association was observed between maternal 25(OH)D in week 30 of gestation and offspring cardio-metabolic risk factors. However, the analyses did suggest a possible inverse association with blood pressure in females.

Conclusions

No clear association between maternal 25(OH)D concentration in week 30 of gestation and cardio-metabolic risk factors in the 20 year old offspring was found.

Vitamin D modulation of innate immune responses to respiratory viral infections

Vitamin D, in addition to its classical functions in bone homeostasis, has a modulatory and regulatory role in multiple processes, including host defense, inflammation, immunity, and epithelial repair. Patients with respiratory disease are frequently deficient in vitamin D, implying that supplementation might provide significant benefit to these patients. Respiratory viral infections are common and are the main trigger of acute exacerbations and hospitalization in children and adults with asthma and other airways diseases. Respiratory monocytes/macrophages and epithelial cells constitutively express the vitamin D receptor. Vitamin D, acting through this receptor, may be important in protection against respiratory infections. Whether the in vitro findings can be translated into a substantial in vivo benefit still remains uncertain. Here we review the in vitro data on the role of vitamin D in antiviral innate immunity, the data concerning the deficient levels of vitamin D in lung diseases, and the in vivo role of supplementation as protection against respiratory viral infections in healthy individuals and in patients with chronic respiratory diseases. Finally, we suggest ways of improving the effectiveness of vitamin D as an adjuvant in the prevention and treatment of acute respiratory infections.

Ultraviolet radiation and effects on humans: the paradigm of maternal vitamin D production during pregnancy

Current evidence indicates that neonates born of mothers with vitamin D deficiency during pregnancy have greater risk for developing hypocalcemia, rickets and extra-skeletal disorders. Despite the classic knowledge that ultraviolet-B (UVB) exposure is the most efficient way for a future mother to obtain optimal vitamin D concentrations, no current consensus or clinical recommendations exist regarding the duration and timing of UVB exposure for pregnant women. This article offers a narrative review of available data regarding how UVB exposure affects maternal vitamin D production during pregnancy, along with a discourse on clinical implications of this public health issue. Future studies would benefit from adopting UVB exposure estimates to recommend appropriate UVB exposure to pregnant women. Doing so could provide a more holistic and practical approach in managing maternal hypovitaminosis D during pregnancy.

An estimate of the economic burden of vitamin D deficiency in pregnant women in the United Kingdom

Pregnancy is associated with an increased risk of vitamin D deficiency beyond that of the general population. The aim of the current analysis was to synthesize the current evidence on the dose-outcome relationship of vitamin D/serum 25 hydroxyvitamin D (25-OHD) and complications during pregnancy. An additional aim was to estimate the economic burden attributable to inadequate levels of serum 25-OHD. Published literature on the effects of vitamin D supplementation/serum 25-OHD on pregnancy complications, including randomized control trials and non-interventional studies, was searched in bibliographic databases including Pubmed, Google Scholar, Scopus and EMBASE. A positive and significant treatment effect was obtained for pre-eclampsia (OR = 0.75 95% CI 0.662-0.843), but not for preterm birth (OR = 0.783, 95% CI 0.49-1.251) or small for gestational age (OR = 0.76 95% CI 0.38-1.28). Inadequate vitamin D accounted for 14.04% of risk for pre-eclampsia. It is estimated that addressing vitamin D inadequacy in pregnant women in England and Wales would reduce the number of cases of pre-eclampsia by 4126; and would result in a net saving of £18.6 million for the NHS in England and Wales. The current results suggest that based on current evidence a public health policy preventing vitamin D inadequacy in pregnant women is likely to have a positive impact on the NHS budget in England and Wales. This is contingent upon further evidence regarding the vitamin D dose-pregnancy outcome relationship becoming available.

Vitamin D status is associated with uteroplacental dysfunction indicated by pre-eclampsia and small-for-gestational-age birth in a large prospective pregnancy cohort in Ireland with low vitamin D status

BACKGROUND

Associations between vitamin D and pregnancy outcomes have been inconsistent.

OBJECTIVES

We described the distribution of 25-hydroxyvitamin D3 [25(OH)D3], 3-epi-25(OH)D3, and 25(OH)D2 in early pregnancy and investigated associations with pre-eclampsia and small-for-gestational-age (SGA) birth, which are indicative of uteroplacental dysfunction.

DESIGN

The SCOPE (Screening for Pregnancy Endpoints) Ireland prospective pregnancy cohort study included 1768 well-characterized low-risk, nulliparous women resident at 52°N. Serum 25(OH)D3, 3-epi-25(OH)D3, and 25(OH)D2 were quantified at 15 wk of gestation with the use of a CDC-accredited liquid chromatography-tandem mass spectrometry method.

RESULTS

The mean ± SD total 25(OH)D concentration was 56.7 ± 25.9 nmol/L, and 17% and 44% of women had 25(OH)D concentrations <30 and <50 nmol/L, respectively. The prevalence of pre-eclampsia was 3.8%, and 10.7% of infants were SGA. There was a lower risk of pre-eclampsia plus SGA combined (13.6%) at 25(OH)D concentrations >75 nmol/L (adjusted OR: 0.64; 95% CI: 0.43, 0.96). The main predictors of 25(OH)D were the use of vitamin D-containing supplements (adjusted mean difference: 20.1 nmol/L; 95% CI: 18.5, 22.7 nmol/L) and summer sampling (adjusted mean difference: 15.5 nmol/L; 95% CI: 13.4, 17.6 nmol/L). Non-Caucasian ethnicity (adjusted mean difference: -19.3 nmol/L; 95% CI: -25.4, -13.2 nmol/L) and smoking (adjusted mean difference: -7.0 nmol/L; 95% CI: -10.5, -3.6 nmol/L) were negative predictors of 25(OH)D. The mean ± SD concentration of 3-epi-25(OH)D3, which was detectable in 99.9% of samples, was 2.6 ± 1.6 nmol/L. Determinants of 3-epi-25(OH)D3 were 25(OH)D3 (adjusted mean difference: 0.052 nmol/L; 95% CI: 0.050, 0.053 nmol/L) and maternal age (adjusted mean difference: -0.018 nmol/L; 95% CI: -0.026, -0.009 nmol/L). The mean ± SD concentration of 25(OH)D2 was 3.1 ± 2.7 nmol/L, which was present in all samples. No adverse effects of 25(OH)D concentrations >125 nmol/L were observed.

CONCLUSIONS

In the first report to our knowledge of CDC-accredited 25(OH)D data and pregnancy outcomes from a large, clinically validated, prospective cohort study, we observed a protective association of a 25(OH)D concentration >75 nmol/L and a reduced risk of uteroplacental dysfunction as indicated by a composite outcome of SGA and pre-eclampsia. Well-designed, adequately powered randomized controlled trials are required to verify this observation. The SCOPE pregnancy cohort was registered at www.anzctr.org.au as ACTRN12607000551493.

Vitamin supplementation in pregnancy

Ensuring that a woman is well-nourished, both before and during pregnancy, is crucial for the health of the woman and that of the unborn child.(1) Maternal deficiency in key nutrients has been linked to pre-eclampsia, restricted fetal growth, neural tube defects, skeletal deformity and low birth weight.(1,2) Many nutritional supplements containing vitamins, minerals and other micronutrients are heavily marketed to women for all stages of pregnancy. However, much of the evidence for vitamin supplementation in pregnancy comes from studies carried out in low-income countries,(3) where women are more likely to be undernourished or malnourished than within the UK population. The challenges lie in knowing which supplements are beneficial and in improving uptake among those at most need. Here we summarise current UK guidance for vitamin supplementation in pregnancy and review the evidence behind it.

The Current Recommended Vitamin D Intake Guideline for Diet and Supplements During Pregnancy Is Not Adequate to Achieve Vitamin D Sufficiency for Most Pregnant Women

Background

The aims of this study were to determine if pregnant women consumed the recommended vitamin D through diet alone or through diet and supplements, and if they achieved the current reference range vitamin D status when their reported dietary intake met the current recommendations.

Methods

Data and banked blood samples collected in second trimester from a subset of 537 women in the APrON (Alberta Pregnant Outcomes and Nutrition) study cohort were examined. Frozen collected plasma were assayed using LC-MS/MS (liquid chromatography-tandem mass spectrometry) to determine 25(OH)D₂, 25(OH)D₃, 3-epi-25(OH)D₃ concentrations. Dietary data were obtained from questionnaires including a Supplement Intake Questionnaire and a 24-hour recall of the previous day’s diet.

Results

Participants were 87% Caucasian; mean (SD) age of 31.3 (4.3); BMI 25.8 (4.7); 58% were primiparous; 90% had education beyond high school; 80% had a family income higher than CAN $70,000/year. 25(OH)D₂, 25(OH)D₃, and 3-epi-25(OH)D₃) were identified in all of the 537 plasma samples;3-epi-25(OH)D₃ contributed 5% of the total vitamin D. The median (IQR) total 25(OH)D (D₂+D₃) was 92.7 (30.4) nmol/L and 20% of women had 25(OH)D concentration < 75 nmol/L. The median (IQR) reported vitamin D intake from diet and supplements was 600 (472) IU/day. There was a significant relationship between maternal reported dietary vitamin D intake (diet and supplement) and 25(OH)D and 3-epi-25(OH)D₃ concentrations in an adjusted linear regression model.

Conclusions

We demonstrated the current RDA (600 IU/ day) may not be adequate to achieve vitamin D status >75 nmol/L in some pregnant women who are residing in higher latitudes (Calgary, 51°N) in Alberta, Canada and the current vitamin D recommendations for Canadian pregnant women need to be re-evaluated.

Maternal vitamin D levels and the risk of perinatal death

OBJECTIVE

To determine the association between maternal vitamin D levels and perinatal death.

METHODS

A retrospective cross-sectional study of all non-anomalous, singleton births (≥24 weeks) with perinatal death compared to a matched control group. Only pregnancies with a recorded vitamin D level at booking (8-19 weeks gestation) were included for analysis. Maternal vitamin D levels were categorized into normal, deficient and insufficient cohorts and variables compared between the three groups.

RESULTS

There were 31 perinatal deaths which were compared to 111 controls. Median vitamin D levels were lower in the perinatal death cohort compared to the control group (55 nmol/L versus 64 nmol/L, p = 0.43). There was no significant increase in deaths between the normal and deficient (p = 0.33) or insufficient (p = 0.09) groups.

CONCLUSIONS

Low maternal vitamin D levels at booking were not associated with an increased risk of perinatal demise.

Maternal vitamin D concentrations during pregnancy, fetal growth patterns, and risks of adverse birth outcomes

BACKGROUND

Maternal vitamin D deficiency during pregnancy may affect fetal outcomes.

OBJECTIVE

The objective of this study was to examine whether maternal 25-hydroxyvitamin D [25(OH)D] concentrations in pregnancy affect fetal growth patterns and birth outcomes.

DESIGN

This was a population-based prospective cohort in Rotterdam, Netherlands in 7098 mothers and their offspring. We measured 25(OH)D concentrations at a median gestational age of 20.3 wk (range: 18.5-23.3 wk). Vitamin D concentrations were analyzed continuously and in quartiles. Fetal head circumference and body length and weight were estimated by repeated ultrasounds, and preterm birth (gestational age <37 wk) and small size for gestational age (less than the fifth percentile) were determined.

RESULTS

Adjusted multivariate regression analyses showed that, compared with mothers with second-trimester 25(OH)D concentrations in the highest quartile, those with 25(OH)D concentrations in the lower quartiles had offspring with third-trimester fetal growth restriction, leading to a smaller head circumference, shorter body length, and lower body weight at birth (all P < 0.05). Mothers who had 25(OH)D concentrations in the lowest quartile had an increased risk of preterm delivery (OR: 1.72; 95% CI: 1.14, 2.60) and children who were small for gestational age (OR: 2.07; 95% CI: 1.33, 3.22). The estimated population attributable risk of 25(OH)D concentrations <50 nmol/L for preterm birth or small size for gestational age were 17.3% and 22.6%, respectively. The observed associations were not based on extreme 25(OH)D deficiency, but presented within the common ranges.

CONCLUSIONS

Low maternal 25(OH)D concentrations are associated with proportional fetal growth restriction and with an increased risk of preterm birth and small size for gestational age at birth. Further studies are needed to investigate the causality of these associations and the potential for public health interventions.

Impact of vitamin D deficiency on maternal and birth outcomes in the Saudi population: a cross-sectional study

Background

Low serum vitamin D [25(OH)D] has been associated with different health problems worldwide. However, its causal role in several diseases remains unclear. We aimed to correlate vitamin D status with maternal and neonatal outcomes in pregnant females.

Method

One thousand pregnant women were recruited during early labour from the labour ward of King Khaled University Hospital, Riyadh, Saudi Arabia. Detailed medical data of all participants were collected from their records. Delivery events and birth outcomes were also documented. Serum 25(OH)D levels were measured using an enzyme-linked immunosorbent assay. A receiver operating characteristic (ROC) curve was constructed to evaluate the ability of vitamin D levels to predict complicated pregnancies. Regression analysis was used to test the correlation between serum 25(OH)D levels and different variables.

Results

Most of the participants were Saudis (89.9 %) and housewives (85.1 %) and 86.4 % of them had vitamin D deficiency (mean: 30.46 ± 19.6 nmol/L). Gestational diabetes mellitus (GDM) was the commonest complication detected (11.1 %) while the history of miscarriage was elevated (24.5 %). There was no association between GDM and low 25(OH)D. Yet, there was a significant negative correlation between serum 25(OH)D levels and fasting blood glucose among females older than 35 years (r = −0.2, p = 0.03). Hypertensive disorders of pregnancy and pre-existing hypertension were less than 1.5 % of frequency. Nevertheless, they were only recorded in women with insufficient and deficient vitamin D. ROC curve revealed that 25(OH)D levels were not able to discriminate between normal and adverse pregnancy outcomes (AUROC curve: 0.51; 95 % confidence interval (CI): 0.44–0.58; p = 0.8).

Conclusion

Hypovitaminosis D, a highly prevalent health problem among pregnant females in Riyadh, has no relation to adverse pregnancy outcomes except for a higher prevalence of miscarriage in women with low 25(OH)D.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-0901-4) contains supplementary material, which is available to authorized users.

Vitamin D Status in Pregnancy and Determinants in a Southern European Cohort Study

BACKGROUND

Population-based data on vitamin D status in pregnancy in southern European countries are scarce. We assessed the prevalence and determinants of vitamin D insufficiency and deficiency in pregnancy in Spain.

METHODS

Plasma 25-hydroxyvitamin D3 (25(OH)D3) concentration was measured at the first trimester of gestation in 2,036 pregnant women from several geographical areas of Spain (latitude 39-42°N). Uni- and multivariable regression models were conducted to identify predictors of circulating 25(OH)D3 concentration and vitamin D insufficiency (20-30 ng/mL) and deficiency (<20 ng/mL).

RESULTS

Thirty-one per cent and 18% of women were vitamin D insufficient and deficient, respectively. Season at blood collection, latitude, age, social class, tobacco smoking, physical activity and use of vitamin D supplements were identified as independent determinants of 25(OH)D3 concentration. Lower risk of vitamin D insufficiency and deficiency was associated with summer season at blood collection (RR for insufficiency = 0.34, confidence intervals (CI) 0.25, 0.48; and RR for deficiency = 0.07, 95% CI 0.04, 0.12), southern latitude (RR for insufficiency = 0.71, 95% CI 0.50, 1.02; RR for deficiency = 0.60, 95% CI 0.38, 0.94); use of vitamin D supplements (RR for insufficiency = 0.50, 95% CI 0.35, 0.71; RR for deficiency = 0.24, 95% CI 0.14, 0.41); and strong physical activity (RR for insufficiency = 0.80, 95% CI 0.58, 1.09; and RR for deficiency = 0.67, 95% CI 0.46, 1.03). Higher risk of vitamin D deficiency was related to lower social class (RR = 1.94, 95% CI 1.19, 3.16) and smoking (RR = 1.76, 95% CI 1.23, 2.54).

CONCLUSIONS

Vitamin D insufficiency and deficiency are highly prevalent in pregnancy. Recommendations and policies to detect and prevent hypovitaminosis D during pregnancy should be developed taking into account the associated factors.

Vitamin D status in mothers with pre-eclampsia and their infants: a case-control study from Serbia, a country without a vitamin D fortification policy

OBJECTIVE

The objective of the present study was to determine if vitamin D intake and status are associated with pre-eclampsia in a country without a vitamin D fortification policy.

DESIGN

A case-control study of pregnancies with (case) and without (control) pre-eclampsia was conducted from January to April when UVB is minimal. Maternal and cord blood obtained at delivery were measured for plasma 25-hydroxycholecalciferol (25-OH-D3), 3-epimer of 25-OH-D3 (3-epi-25-OH-D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) by LC-MS/MS and maternal 1,25-dihydroxyvitamin D (1,25-(OH)2D). Differences between groups were tested with ANOVA and Bonferroni post hoc tests (P<0·05).

SETTING

Clinical Center of Serbia.

SUBJECTS

Pregnant women with and without pre-eclampsia (n 60) and their infants.

RESULTS

Exogenous vitamin D intake (0·95-16·25 µg/d (38-650 IU/d)) was not significantly different between groups. Women with pre-eclampsia delivered infants at an earlier gestational age and had significantly lower mean total plasma 25-hydroxyvitamin D (25-OH-D; case: 11·2 (sd 5·1); control: 16·1 (sd 5·7) ng/ml; P=0·0006), 25-OH-D3 (case: 10·0 (sd 4·9); control: 14·2 (sd 5·8) ng/ml; P=0·002), 3-epi-25-OH-D3 (case: 0·5 (sd 0·2); control: 0·7 (sd 0·2) ng/ml; P=0·0007) and 1,25-(OH)2D (case: 56·5 (sd 26·6); control: 81·0 (sd 25·7) pg/ml; P=0·018), while 24,25-(OH)2D3 was not different between groups. Infants did not differ in total plasma 25-OH-D, 25-OH-D3, 3-epi-25-OH-D3 and 24,25-(OH)2D3, but the mean proportion of 3-epi-25-OH-D3 was higher in the infant case group (case: 7·9 (sd 1·1); control: 7·0 (sd 1·4) % of total 25-OH-D3; P=0·005).

CONCLUSIONS

A high prevalence of vitamin D deficiency, as defined by plasma 25-OH-D<12 ng/ml, was observed in 47 % of all mothers and 77 % of all infants. These data underscore the need for prenatal vitamin D supplementation and a food fortification policy in Serbia.

Maternal and cord blood vitamin D status and childhood infection and allergic disease: a systematic review

CONTEXT

It is unclear how in utero vitamin D deficiency affects the extraskeletal health of children, despite the known risks for adverse pregnancy/birth outcomes.

OBJECTIVE

This systematic review seeks to assess the effect of in utero vitamin D exposure on childhood allergy and infection outcomes using the PRISMA guidelines.

DATA SOURCES

MEDLINE, Cochrane Library, and Web of Science databases were searched.

STUDY SELECTION

Literature published through April 2015 was searched for studies reporting on the association between maternal pregnancy or cord blood vitamin D status and childhood allergy and infection.

DATA EXTRACTION

Of 4175 articles identified, 43 studies met the inclusion criteria. They examined a wide variety of outcomes, using many different vitamin D cutoff values in their analyses.

DATA SYNTHESIS

For most outcomes, results were inconsistent, although there appeared to be a protective effect between higher in utero vitamin D status and childhood lower respiratory tract infection (5 of 10 studies).

CONCLUSIONS

More research is needed on childhood allergy and infection outcomes, and future studies should standardize outcome reporting, especially with regard to cutoff values for vitamin D concentrations. Evidence of a protective association between in utero vitamin D exposure and lower respiratory tract infection was found, while the other outcomes were either understudied or showed inconsistent results.PROSPERO registration no. CRD42013006156.

Epigenetic Biomarkers of Preterm Birth and Its Risk Factors

A biomarker is a biological measure predictive of a normal or pathogenic process or response. Biomarkers are often useful for making clinical decisions and determining treatment course. One area where such biomarkers would be particularly useful is in identifying women at risk for preterm delivery and related pregnancy complications. Neonates born preterm have significant morbidity and mortality, both in the perinatal period and throughout the life course, and identifying women at risk of delivering preterm may allow for targeted interventions to prevent or delay preterm birth (PTB). In addition to identifying those at increased risk for preterm birth, biomarkers may be able to distinguish neonates at particular risk for future complications due to modifiable environmental factors, such as maternal smoking or alcohol use during pregnancy. Currently, there are no such biomarkers available, though candidate gene and epigenome-wide association studies have identified DNA methylation differences associated with PTB, its risk factors and its long-term outcomes. Further biomarker development is crucial to reducing the health burden associated with adverse intrauterine conditions and preterm birth, and the results of recent DNA methylation studies may advance that goal.

Use of a web-based dietary assessment tool in early pregnancy

BACKGROUND

Maternal diet is critical to fetal development and lifelong health outcomes. In this context, dietary quality indices in pregnancy should be explicitly underpinned by data correlating food intake patterns with nutrient intakes known to be important for gestation.

AIMS

Our aim was to assess the correlation between dietary quality scores derived from a novel online dietary assessment tool (DAT) and nutrient intake data derived from the previously validated Willett Food Frequency Questionnaire (WFFQ).

METHODS

524 women completed the validated semi-quantitive WFFQ and online DAT questionnaire in their first trimester. Spearman correlation and Kruskal-Wallis tests were used to test associations between energy-adjusted and energy-unadjusted nutrient intakes derived from the WFFQ, and diet and nutrition scores obtained from the DAT.

RESULTS

Positive correlations were observed between respondents' diet and nutrition scores derived from the online DAT, and their folate, vitamin B12, iron, calcium, zinc and iodine intakes/MJ of energy consumed derived from the WFFQ (all P < 0.001). Negative correlations were observed between participants' diet and nutrition scores and their total energy intake (P = 0.02), and their percentage energy from fat, saturated fat, and non-milk extrinsic sugars (NMES) (all P ≤ 0.001). Median dietary fibre, beta carotene, folate, vitamin C and vitamin D intakes derived from the WFFQ, generally increased across quartiles of diet and nutrition score (all P < 0.001).

CONCLUSIONS

Scores generated by this web-based DAT correlate with important nutrient intakes in pregnancy, supporting its use in estimating overall dietary quality among obstetric populations.

Effect of vitamin D replacement on maternal and neonatal outcomes: a randomised controlled trial in pregnant women with hypovitaminosis D. A protocol

INTRODUCTION

The vitamin D recommended doses during pregnancy differ between societies. The WHO guidelines do not recommend routine prenatal supplementation, but they underscore the fact that women with the lowest levels may benefit most. The effects of routine supplementation during pregnancy on maternal and neonatal clinical outcomes have not been investigated in the Middle East, where hypovitaminosis D is prevalent. Our hypothesis is that in Middle Eastern pregnant women, a vitamin D dose of 3000 IU/day is required to reach a desirable maternal 25-hydroxyvitamin D [25(OH)D] level, and to positively impact infant bone mineral content (BMC).

METHODS AND ANALYSIS

This is a multicentre blinded randomised controlled trial. Pregnant women presenting to the Obstetrics and Gynaecology clinics will be approached. Eligible women will be randomised to daily equivalent doses of cholecalciferol, 600 IU or 3000 IU, from 15 to 18 weeks gestation until delivery. Maternal 25(OH)D and chemistries will be assessed at study entry, during the third trimester and at delivery. Neonatal anthropometric variables and 25(OH)D level will be measured at birth, and bone and fat mass assessment by dual-energy X-ray absorptiometry scan at 1 month. A sample size of 280 pregnant women is needed to demonstrate a statistically significant difference in the proportion of women reaching a 25(OH)D level ≥ 50 nmol/L at delivery, and a difference in infant BMC of 6 (10)g, for a 90% power and a 2.5% level of significance. The proportions of women achieving a target 25(OH)D level will be compared between the two arms, using χ(2). An independent t test will be used to compare mean infant BMC between the two arms. The primary analysis is an intention-to-treat analysis of unadjusted results.

ETHICS AND DISSEMINATION

The protocol has been approved by the Institutional Review Board at the American University of Beirut-Lebanon (IM.GEHF.22). The trial results will be published in peer-reviewed medical journals and presented at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT02434380.

Dynamics of Vitamin D Metabolism in Maternal-Fetal Dyads

OBJECTIVES

Metabolites of vitamin D in maternal-neonatal dyads remain relatively unexplored. The goal of this study was to evaluate concentrations of 25(OH)D3, 24,25(OH)2D3, and 3-epi-25(OH)D3 in maternal-infant pairs at delivery.

METHODS

Serum samples of maternal and infant cord blood were collected on 131 mother-infant pairs at delivery. Vitamin D metabolites were analyzed in triplicate using liquid chromatography-tandem mass spectrometry. Statistical analysis was conducted using the Fisher exact test, Wilcoxon rank sum test, and Spearman correlation coefficients.

RESULTS

Mean 25(OH)D3 concentrations in maternal and cord blood were 32.9 and 18.5 ng/mL, respectively; mean maternal and cord 24,25(OH)2D3 were 2.0 versus 1.1 ng/mL, respectively. Absolute concentrations of 3-epi-25(OH)D3 were similar in maternal and cord samples (2.4 vs 2.2 ng/mL), whereas the proportion of the total 25(OH)D as the 3-epimer was 6.5% in maternal samples and 10.5% in cord samples. This suggests that the fetus contributes significantly to 3-epi-25(OH)D3 production. In contrast, the ratio of 25(OH)D3:24,25(OH)2D3 was identical in maternal and cord samples (18.5) suggesting equivalent CYP24A1 activity in mother and fetus. Maternal and cord metabolite levels were highly correlated (r = 0.78, 0.90, 0.89 for 25(OH)D3, 24,25(OH)2D3, and 3-epi-25(OH)D3, respectively, P = 0.001 for all). Serum concentrations of all metabolites were lower in nonwhite infants compared with white infants. Maternal and cord concentrations of 25(OH)D3 were positively associated with birth weight (r = 0.21, P = 0.02; r = 0.25, P = 0.003, respectively).

CONCLUSIONS

This data suggests that although maternal and cord concentrations of vitamin D metabolites are highly correlated, regulation of specific vitamin D metabolites in the mother and the neonate may be mediated independently.

Maternal Serum 25-Hydroxyvitamin D Concentrations during Pregnancy and Infant Birthweight for Gestational Age: a Three-Cohort Study

BACKGROUND

In response to inconsistent findings, we investigated associations between maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations and infant birthweight for gestational age (BW/GA), including potential effect modification by maternal race/ethnicity and infant sex.

METHODS

Data from 2558 pregnant women were combined in a nested case-control study (preterm and term) sampled from three cohorts: the Omega study, the Pregnancy, Infection and Nutrition study, and the Pregnancy Outcomes and Community Health study. Maternal 25(OH)D concentrations were sampled at 4 to 29 weeks gestation (80% 14-26 weeks). BW/GA was modelled as sex and gestational age-specific birthweight z-scores. General linear regression models (adjusting for age, education, parity, pre-pregnancy body mass index, season at blood draw, and smoking) assessed 25(OH)D concentrations in relation to BW/GA.

RESULTS

Among non-Hispanic Black women, the positive association between 25(OH)D concentrations and BW/GA was of similar magnitude in pregnancies with female or male infants [beta (β) = 0.015, standard error (SE) = 0.007, P = 0.025; β = 0.018, SE = 0.006, P = 0.003, respectively]. Among non-Hispanic White women, 25(OH)D-BW/GA association was observed only with male infants, and the effect size was lower (β = 0.008, SE = 0.003, P = 0.02).

CONCLUSIONS

Maternal serum concentrations of 25(OH)D in early and mid-pregnancy were positively associated with BW/GA among non-Hispanic Black male and female infants and non-Hispanic White male infants. Effect modification by race/ethnicity may be due, in part, to overall lower concentrations of 25(OH)D in non-Hispanic Blacks. Reasons for effect modification by infant sex remain unclear.

Vitamin D deficiency and supplementation in pregnancy in a multiethnic population-based cohort

BACKGROUND

To investigate ethnic differences in vitamin D levels during pregnancy, assess risk factors for vitamin D deficiency and explore the effect of vitamin D supplementation in women with deficiency in early pregnancy.

METHODS

This is a population-based, multiethnic cohort study of pregnant women attending Child Health Clinics for antenatal care in Oslo, Norway. Serum-25-hydroxyvitamin D [25(OH)D] was measured in 748 pregnant women (59% ethnic minorities) at gestational weeks (GW) 15 (SD:3.6) and 28 (1.4). Women with 25(OH)D <37 nmol/L at GW 15 were for ethical reasons recommended vitamin D3 supplementation. Main outcome measure was 25(OH)D, and linear regression models were performed.

RESULTS

Severe deficiency (25(OH)D <25 nmol/L) was found at GW 15 in 45% of women from South Asia, 40% from the Middle East and 26% from Sub-Saharan Africa, compared to 2.5% in women from East Asia and 1.3% of women from Western Europe. Women from South Asia, the Middle East and Sub-Saharan Africa had mean values that were -28 (95 % CI:-33, -23), -24 (-29, -18) and -20 (-27, -13) nmol/L lower than in Western women, respectively. Ethnicity, education, season and intake of vitamin D were independently associated with 25(OH)D. At GW 28, the mean 25(OH)D had increased from 23 (SD:7.8) to 47 (27) nmol/L (p < 0.01) in women who were recommended vitamin D supplementation, with small or no change in women with sufficient vitamin D levels at baseline.

CONCLUSIONS

Vitamin D deficiency was prevalent among South Asian, Middle Eastern and African women. The serum levels of 25(OH)D increased significantly from GW 15 to 28 in vitamin D deficient women who received a recommendation for supplementation. This recommendation of vitamin D supplementation increased vitamin D levels in deficient women.

Vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D deficiency or insufficiency is thought to be common among pregnant women. Vitamin D supplementation during pregnancy has been suggested as an intervention to protect against adverse pregnancy outcomes.

OBJECTIVES

To examine whether oral supplements with vitamin D alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve maternal and neonatal outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (23 February 2015), the International Clinical Trials Registry Platform (31 January 2015), the Networked Digital Library of Theses and Dissertations (28 January 2015) and also contacted relevant organisations (31 January 2015).

SELECTION CRITERIA

Randomised and quasi-randomised trials with randomisation at either individual or cluster level, evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy.

DATA COLLECTION AND ANALYSIS

Two review authors independently i) assessed the eligibility of studies against the inclusion criteria ii) extracted data from included studies, and iii) assessed the risk of bias of the included studies. Data were checked for accuracy. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

In this updated review we included 15 trials assessing a total of 2833 women, excluded 27 trials, and 23 trials are still ongoing or unpublished. Nine trials compared the effects of vitamin D alone versus no supplementation or a placebo and six trials compared the effects of vitamin D and calcium with no supplementation. Risk of bias in the majority of trials was unclear and many studies were at high risk of bias for blinding and attrition rates. Vitamin D alone versus no supplementation or a placebo Data from seven trials involving 868 women consistently show that women who received vitamin D supplements alone, particularly on a daily basis, had higher 25-hydroxyvitamin D than those receiving no intervention or placebo, but this response was highly heterogeneous. Also, data from two trials involving 219 women suggest that women who received vitamin D supplements may have a lower risk of pre-eclampsia than those receiving no intervention or placebo (8.9% versus 15.5%; risk ratio (RR) 0.52; 95% CI 0.25 to 1.05, low quality). Data from two trials involving 219 women suggest a similar risk of gestational diabetes among those taking vitamin D supplements or no intervention/placebo (RR 0.43; 95% CI 0.05, 3.45, very low quality). There were no clear differences in adverse effects, with only one reported case of nephritic syndrome in the control group in one study (RR 0.17; 95% CI 0.01 to 4.06; one trial, 135 women, low quality). Given the scarcity of data for this outcome, no firm conclusions can be drawn. No other adverse effects were reported in any of the other studies.With respect to infant outcomes, data from three trials involving 477 women suggest that vitamin D supplementation during pregnancy reduces the risk preterm birth compared to no intervention or placebo (8.9% versus 15.5%; RR 0.36; 95% CI 0.14 to 0.93, moderate quality). Data from three trials involving 493 women also suggest that women who receive vitamin D supplements during pregnancy less frequently had a baby with a birthweight below 2500 g than those receiving no intervention or placebo (RR 0.40; 95% CI 0.24 to 0.67, moderate quality).In terms of other outcomes, there were no clear differences in caesarean section (RR 0.95; 95% CI 0.69 to 1.31; two trials; 312 women); stillbirths (RR 0.35 95% CI 0.06, 1.99; three trials, 540 women); or neonatal deaths (RR 0.27; 95% CI 0.04, 1.67; two trials, 282 women). There was some indication that vitamin D supplementation increases infant length (mean difference (MD) 0.70, 95% CI -0.02 to 1.43; four trials, 638 infants) and head circumference at birth (MD 0.43, 95% CI 0.03 to 0.83; four trials, 638 women). Vitamin D and calcium versus no supplementation or a placeboWomen who received vitamin D with calcium had a lower risk of pre-eclampsia than those not receiving any intervention (RR 0.51; 95% CI 0.32 to 0.80; three trials; 1114 women, moderate quality), but also an increased risk of preterm birth (RR 1.57; 95% CI 1.02 to 2.43, three studies, 798 women, moderate quality). Maternal vitamin D concentration at term, gestational diabetes, adverse effects and low birthweight were not reported in any trial or reported only by one study.

AUTHORS' CONCLUSIONS

New studies have provided more evidence on the effects of supplementing pregnant women with vitamin D alone or with calcium on pregnancy outcomes. Supplementing pregnant women with vitamin D in a single or continued dose increases serum 25-hydroxyvitamin D at term and may reduce the risk of pre-eclampsia, low birthweight and preterm birth. However, when vitamin D and calcium are combined, the risk of preterm birth is increased. The clinical significance of the increased serum 25-hydroxyvitamin D concentrations is still unclear. In light of this, these results need to be interpreted with caution. Data on adverse effects were lacking in all studies.The evidence on whether vitamin D supplementation should be given as a part of routine antenatal care to all women to improve maternal and infant outcomes remains unclear. While there is some indication that vitamin D supplementation could reduce the risk of pre-eclampsia and increase length and head circumference at birth, further rigorous randomised trials are required to confirm these effects.

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

Functional deficiencies of the immune system are known to predispose human and animal neonates to death. Thus, immune competency may be a significant factor influencing the mortality of lambs. Vitamin D has been recognised to improve immune function and is transferred across the placenta. This study tested the hypotheses that (1) supplementation of Merino ewes with cholecalciferol during late pregnancy will increase the concentrations of vitamin D in the ewe and lamb at birth and (2) supplementation of Merino ewes with cholecalciferol during late pregnancy is correlated with an increase in innate phagocytic and adaptive antibody immune responses in the lamb. Merino ewes (n = 53) were injected intramuscularly with 1 × 106 IU cholecalciferol at Days 113 and 141 of pregnancy. A control group (n = 58) consisted of ewes receiving no additional nutritional treatments. The vitamin D status of ewes and lambs was assessed up until 1 month post-lambing. Lamb immune function was assessed by analysing the functional capacity of phagocytes, and the plasma IgG and anti-tetanus-toxoid antibody concentrations between birth and weaning. Maternal supplementation with cholecalciferol increased the plasma 25(OH)D concentrations of both ewes (137 vs 79 nmol/L; P < 0.001) and lambs (49 vs 24 nmol/L; P < 0.001) at birth compared with the controls. Supplementation with cholecalciferol had no significant effect on the phagocytic capacity of monocytes or polymorphonuclear leukocytes, the concentration of IgG in the colostrum or plasma of lambs, or the vaccine-specific antibody response against tetanus toxoid. Overall, the results support our first hypothesis, but suggest that maternal supplementation with 1 × 106 IU cholecalciferol does not improve innate, passive or adaptive immune function in lambs.

Potential impact of maternal vitamin D status on obstetric well-being

Despite its discovery 100 years ago, vitamin D (VD) has emerged as one of the most controversial nutrients and prohormones of the 21st century. In the past few years, a growing interest in VD has been observed in the biomedical literature due to evidences demonstrating a relevant relationship not only between regulation of calcium and phosphorus homeostasis, but also multiple disease states and low VD status in the population. Indeed, several studies carried out to decipher its role in the body in almost every cell, tissue, and different organs. Recent findings suggested a significant implication of VD in different physiologic processes , such as vascular health, immune function, metabolism, and placental function. In the attempt to focus the attention on effect of VD on female reproductive health, there has been a paucity of data from randomized controlled trials to establish clear beneficial. Human and animal data suggest that low VD status is associated with impaired fertility, endometriosis, and polycystic ovary syndrome. Findings from observational studies show higher rates of preeclampsia, gestational diabetes, preterm birth, and bacterial vaginosis in women with low VD levels. By recent evidences, this review explored the association between maternal VD status and selected effects on maternal, perinatal, and infant health, and the impact of VD supplementation during pregnancy on obstetric well-being.

Early pregnancy vitamin D status and risk for adverse maternal and infant outcomes in a bi-ethnic cohort: the Behaviors Affecting Baby and You (B.A.B.Y.) Study

Vitamin D deficiency is common during pregnancy and higher in Hispanic as compared with non-Hispanic white women. However, the association between vitamin D deficiency and adverse pregnancy outcomes remains unclear and may vary across ethnic groups, in part because of genetic variation in the metabolism of vitamin D. Few studies have included Hispanic women. Therefore, we investigated this association among 237 participants in the Behaviors Affecting Baby and You Study, a randomised trial of an exercise intervention among ethnically diverse prenatal care patients in Massachusetts. Baseline serum 25-hydroxyvitamin D (25(OH)D) was measured at 15·2 (sd 4·7) weeks' gestation. Information on adverse pregnancy outcomes was abstracted from medical records. Mean 25(OH)D was 30·4 (sd 12·0) ng/ml; 53·2 % of participants had insufficient (<30 ng/ml) and 20·7 % had deficient (<20 ng/ml) 25(OH)D levels. After adjusting for month of blood draw, gestational age at blood draw, gestational age at delivery, age, BMI and Hispanic ethnicity, women with insufficient and deficient vitamin D had infants with birth weights 139·74 (se 69·16) g (P=0·045) and 175·52 (se 89·45) g (P=0·051) lower compared with women with sufficient vitamin D levels (≥30 ng/ml). Each 1 ng/ml increase in 25(OH)D was associated with an increased risk for gestational diabetes mellitus among Hispanic women only (relative risk 1·07; 95 % CI 1·03, 1·11) in multivariable analysis. We did not observe statistically significant associations between maternal vitamin D status and other pregnancy outcomes. Our findings provide further support for an adverse impact of vitamin D deficiency on birth weight in Hispanic women.

Vitamin D deficiency and dyslipidemia in early pregnancy

Background

Vitamin D deficiency is a common nutritional issue and dietary supplementation in the general population, including pregnant women, is generally advised. Appropriately high levels of vitamin D are expected to play a role in containing the glycemic and atherogenic profiles observed in pregnancy. However, the relation between vitamin D status and the lipid metabolic profile in Saudi women, who are known to suffer from chronic vitamin D deficiency and high incidence of obesity and type II DM, during the course of pregnancy is not known.

Methods

In this study, we analyzed the relation between serum vitamin D level and various serum metabolic markers among Saudi women (n = 515) in their first trimester of pregnancy (11.2 ± 3.4 weeks). Coefficients of Pearson correlation and Spearman rank correlation were calculated for Gaussian and non-Gaussian variables, respectively. Serum vitamin D status was defined as (in nmol/L): deficient (<25), insufficient (25–50); sufficient (50–75) and desirable (>75).

Results

Results indicated that vitamin D status was sufficient in only 3.5 % of the study participants and insufficient and deficient in 26.2 % and 68.0 % of participants, respectively. Serum vitamin D values in the overall study population correlated positively with serum levels of total cholesterol (R = 0.172; p < 0.01), triglycerides (R = 0.184; p < 0.01) and corrected calcium (R = 0.141; p < 0.05). In the subgroup of vitamin D deficient subjects (n = 350), log serum vitamin D values correlated with serum triglycerides (R = 0.23; p = 0.002) and cholesterol (R = 0.26; p = 0.001).

Conclusions

The positive correlations between serum vitamin D and the atherogenic factors such as total cholesterol and triglycerides indicate a pro-atherogenic metabolic status in vitamin D deficient expectant mothers. This may represent an adaptation to the high metabolic demands of pregnancy.

High prevalence of vitamin D deficiency among women of child-bearing age in Lahore Pakistan, associating with lack of sun exposure and illiteracy

BACKGROUND

Vitamin D status is a key determinant of maternal and neonatal health. Deficiency has been reported to be common in Pakistani women, but information regarding environmental and genetic determinants of vitamin D status is lacking in this population.

METHODS

We conducted a cross-sectional study among three groups of healthy women living in Lahore, Pakistan: university students, students or employees of Medrasas or Islamic Institutes, and employees working in office, hospital or domestic settings. Multivariate analysis was performed to identify environmental and genetic determinants of vitamin D status: polymorphisms in genes encoding the vitamin D receptor, vitamin D 25-hydroxylase enzyme CYP2R1 and vitamin D binding protein [DBP] were investigated. We also conducted analyses to identify determinants of body ache and bone pain in this population, and to determine the sensitivity and specificity of testing for hypocalcaemia and raised serum alkaline phosphatase to screen for vitamin D deficiency.

RESULTS

Of 215 participants, 156 (73 %) were vitamin D deficient (serum 25[OH]D <50 nmol/L). Risk of vitamin D deficiency was independently associated with illiteracy (adjusted OR 4.0, 95 % CI 1.03-15.52, P = 0.04), <30 min sun exposure per day (adjusted OR 2.13, 95 % CI 1.08-4.19, P = 0.02), sampling in January to March (adjusted OR 2.38, 95 % CI 1.20-4.70), P = 0.01) and lack of regular intake of multivitamins (adjusted OR 2.61, 95 % CI 1.32-5.16, p = 0.005). Participants with the GG genotype of the rs4588 polymorphism in the gene encoding vitamin D binding protein tended to have lower 25(OH)D concentrations than those with GT/TT genotypes (95 % CI for difference 22.7 to -0.13 nmol/L, P = 0.053). Vitamin D deficiency was independently associated with increased risk of body ache or bone pain (adjusted OR 4.43, 95 % CI 2.07 to 9.49, P = 0.001). Hypocalcaemia (serum calcium concentration ≤9.5 mg/dL) and raised alkaline phosphatase concentration (≥280 IU/L) had low sensitivity and very low specificity for identification of vitamin D deficiency.

CONCLUSION

Vitamin D deficiency is common among healthy women of child-bearing age in Lahore, Pakistan: illiteracy, decreased sun exposure and lack of multivitamin intake are risk factors.

Season of birth is associated with birth weight, pubertal timing, adult body size and educational attainment: a UK Biobank study

Season of birth, a marker of in utero vitamin D exposure, has been associated with a wide range of health outcomes. Using a dataset of ∼450,000 participants from the UK Biobank study, we aimed to assess the impact of this seasonality on birth weight, age at menarche, adult height and body mass index (BMI). Birth weight, age at menarche and height, but not BMI, were highly significantly associated with season of birth. Individuals born in summer (June-July-August) had higher mean birth weight (P = 8 × 10^-10), later pubertal development (P = 1.1 × 10^-45) and taller adult height (P = 6.5 × 10^-9) compared to those born in all other seasons. Concordantly, those born in winter (December-January-February) showed directionally opposite differences in these outcomes. A secondary comparison of the extreme differences between months revealed higher odds ratios [95% confidence intervals (CI)] for low birth weight in February vs. September (1.23 [1.15-1.32], P = 4.4 × 10^-10), for early puberty in September vs. July (1.22 [1.16-1.28], P = 7.3 × 10^-15) and for short stature in December vs. June (1.09 [1.03-1.17], P = 0.006). The above associations were also seen with total hours of sunshine during the second trimester, but not during the first three months after birth. Additional associations were observed with educational attainment; individuals born in autumn vs. summer were more likely to continue in education post age 16 years (P = 1.1 × 10^-91) or attain a degree-level qualification (P = 4 × 10^-7). However, unlike other outcomes, an abrupt difference was seen between those born in August vs. September, which flank the start of the school year. Our findings provide support for the 'fetal programming' hypothesis, refining and extending the impact that season of birth has on childhood growth and development. Whilst other mechanisms may contribute to these associations, these findings are consistent with a possible role of in utero vitamin D exposure.

Vitamin D and the development of allergic disease: how important is it?

Vitamin D has known effects on lung development and the immune system that may be important in the development, severity, and course of allergic diseases (asthma, eczema, and food allergy). Vitamin D deficiency is prevalent worldwide and may partly explain the increases in asthma and allergic diseases that have occurred over the last 50-60 years. In this review, we explore past and current knowledge on the effect of vitamin D on lung development and immunomodulation and present the evidence of its role in allergic conditions. While there is growing observational and experimental evidence for the role of vitamin D, well-designed and well-powered clinical trials are needed to determine whether supplementation of vitamin D should be recommended in these disorders.

Comparison of Vitamin D levels in cases with preeclampsia, eclampsia and healthy pregnant women

The aim of this study is to assess vitamin D levels in eclampsia, preeclampsia and healthy pregnant women and the role of vitamin D deficiency in the etiology of preeclampsia (PE). Forty healthy pregnant women, 83 preeclamptic and 32 eclamptic pregnant women were included. Maternal and infant medical records were reviewed. Blood samples were obtained from all groups. Demographics and serum vitamin D levels were compared between the groups. No statistical differences were observed in age, gravidity, parity, weight, height and BMI between the three groups. Week of pregnancy and weight at birth in eclamptic and preeclamptic patients were lower compared to the healthy patients (P<0.001 and P<0.001, respectively). Systolic and diastolic blood pressures were higher in eclamptic (P<0.001) and preeclamptic patients (P<0.001) compared to the healthy pregnant group. The rate of cesarean section was found to be higher in preeclamptic and eclamptic patients (P<0.001). Vitamin D levels were lower in both preeclamptic and eclamptic patients compared to healthy normotensive pregnant women (P<0.001). Preeclamptic and eclamptic women were similar in terms of the data compared. Vitamin D supplementation is considered to decrease the risk of both preeclampsia and eclampsia in the patient population at risk for vitamin D deficiency.

The Relationship between Maternal Vitamin D Deficiency and Low Birth Weight Neonates

OBJECTIVE

Maternal hypovitaminosis D may impair fetal growth and cause adverse pregnancy outcomes including intrauterine growth restriction and neonatal low birth weight. The aim of this study is to evaluate the relationship between maternal vitamin D status and neonate's birth weight.

MATERIALS AND METHODS

A cross-sectional, descriptive analytical study was carried out in the nursery ward of 2 hospitals (Tehran-Iran) during one year (January 2011- January 2012). One hundred and two neonates were categorized into two groups, neonates with birth weight< 2500 gr (n=52) and neonates with birth weight>2500 gr (n = 50). Data regarding medical history, physical examination and anthropometric measurements of neonates were noted in a questionnaire. Birth time blood samples of their mothers were analyzed for serum 25-(OH)-vitamin D by ELISA method. Maternal vitamin D status was compared in two groups.

RESULTS

Mean maternal vitamin D (vit D) level was 31.46 nmol/L. Forty eight percent of mothers had vitamin D deficiency, 27.5% had vit D insufficiency and 24.5% were normal. Mean maternal vitamin D level of LBW neonates was lower than other group; 25.05 vs. 38.13 (p = 0.001). All mothers of neonates with head circumference ≤ 33 cm also had vitamin D deficiency (p = 0.007).

CONCLUSION

Maternal Vitamin D deficiency may increase the risk of low birth weight neonate and modifying maternal nutrition behavior and their vit D level could be beneficial on pregnancy outcome.

Vitamin D metabolism in the premature newborn: A randomized trial

BACKGROUND & AIMS

Vitamin D status during infancy has been associated with important pediatric health outcomes; however concentrations of many vitamin D metabolites in premature infants are not yet described. The objective of this study was to evaluate concentrations of 25(OH)D3, 24,25(OH)2D3, and 3-epi-25(OH)D3 in premature infants.

METHODS

32 infants <32 weeks gestation were randomized to receive 400 or 800IU/day of vitamin D3 orally. Vitamin D metabolites from serum obtained monthly were analyzed in triplicate using a novel, very sensitive Liquid Chromatography-Tandem Mass Spectrometry-based method. Statistical analysis was conducted using the Fisher's exact test, Wilcoxon Rank Sum test, and Spearman correlation coefficients. Measurements over time were fit with linear mixed effect models. A p-value of <0.05 was considered statistically significant.

RESULTS

Mean serum 25(OH)D3 concentrations in cord blood were 17.3 ng/mL; mean 3-epi-25(OH)D3 were 1.3 ng/mL, mean 24,25(OH)2D3 were 1.4 ng/mL. Both 25(OH)D3 and 3-epi-25(OH)D3 increased significantly over time, and the percent of total 25(OH)D3 concentration that was 3-epi-25(OH)D3 also increased significantly (7.2% vs. 29.7%, p < 0.0001 for cord blood vs. 8 weeks). Serum 25(OH)D3:24,25(OH)2D3 ratios at weeks 4 and 8 were higher than ratios reported in older children and adults.

CONCLUSION

Vitamin D metabolism in infants appears to have distinct differences from adults. Vitamin D supplementation was effective in raising 25(OH)D3 concentrations; however significant increases in 3-epi-25(OH)D3 also occurred. Increased 25(OH)D3: 24,25(OH)2D3 ratios in premature infants may be due to immature expression of CYP24A1. Further work is necessary to determine if there are developmental advantages to this unique vitamin D metabolism.

ENDOCRINOLOGY IN PREGNANCY: Influence of maternal vitamin D status on obstetric outcomes and the fetal skeleton

Vitamin D status has been increasingly associated with wide-ranging clinical outcomes. There is now a wealth of observational studies reporting on its associations with obstetric complications, including pre-eclampsia, gestational diabetes and the mode and timing of delivery. The findings are inconsistent, and currently there is a lack of data from high-quality intervention studies to confirm a causal role for vitamin D in these outcomes. This is similarly true with regards to fetal development, including measures of fetal size and skeletal mineralisation. Overall, there is an indication of possible benefits of vitamin D supplementation during pregnancy for offspring birthweight, calcium concentrations and bone mass as well as for reduced maternal pre-eclampsia. However, for none of these outcomes is the current evidence base conclusive, and the available data justify the instatement of high-quality randomised placebo controlled trials in a range of populations and health care settings to establish the potential efficacy and safety of vitamin D supplementation to improve particular outcomes.

Maternal vitamin D supplementation during pregnancy and lactation to promote infant growth in Dhaka, Bangladesh (MDIG trial): study protocol for a randomized controlled trial

Background

Vitamin D regulates bone mineral metabolism and skeletal development. Some observational studies have suggested that prenatal vitamin D deficiency increases the risk of adverse pregnancy and/or birth outcomes; however, there is scant evidence from controlled trials, leading the World Health Organization to advise against routine vitamin D supplementation in pregnancy. Importantly, little is known about the effect of maternal vitamin D status on infant linear growth in communities in South Asia where stunting is highly prevalent and maternal-infant vitamin D status is commonly suboptimal.

Methods/Design

The Maternal Vitamin D for Infant Growth study is a randomized, placebo-controlled, dose-ranging trial of maternal vitamin D supplementation during pregnancy and lactation in Dhaka, Bangladesh. The primary aims are to estimate (1) the effect of maternal prenatal oral vitamin D₃ supplementation (4200 IU/wk, 16,800 IU/wk, or 28,000 IU/wk, administered as weekly doses) versus placebo on infant length at 1 year of age and (2) the effect of maternal postpartum oral vitamin D₃ supplementation (28,000 IU/wk) versus placebo on length at 1 year of age among infants born to women who received vitamin D 28,000 IU/wk during pregnancy. Generally healthy pregnant women (n = 1300) in the second trimester (17–24 weeks of gestation) are randomized to one of five parallel arms: placebo 4200 IU/wk, 16,800 IU/wk, or 28,000 IU/wk in the prenatal period and placebo in the postpartum period or 28,000 IU/wk in the prenatal period and 28,000 IU/wk in the postpartum period. Household- and clinic-based follow-up of mother-infant pairs is conducted weekly by trained personnel until 26 weeks postpartum and every 3 months thereafter. The primary trial outcome measure is length for age z-score at 1 year of age. Anthropometric measurements, clinical information, and biological specimens collected at scheduled intervals will enable the assessment of a range of maternal, perinatal, and infant outcomes.

Discussion

The role of vitamin D in maternal and infant health remains unresolved. This trial is expected to contribute unique insights into the effects of improving maternal-infant vitamin D status in a low-income setting where stunting and adverse perinatal outcomes represent significant public health burdens.

Trial registration

ClinicalTrials.gov identifier: NCT01924013. Registered on 13 August 2013

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-015-0825-8) contains supplementary material, which is available to authorized users.

A review of the literature regarding nutritional supplements and their effect on vaginal flora and preterm birth

PURPOSE OF REVIEW

The aim of this review was to evaluate recently published review articles which examine the use of nutritional supplements to prevent preterm birth (PTB) by modifying vaginal bacteria.

RECENT FINDINGS

Probiotics, vitamin D and vitamin C were all identified as nutritional supplements that have the potential to alter bacterial flora and consequently reduce PTB and treat or prevent genital infections. Evidence shows that probiotics may reduce the incidence of PTB as well as being effective at treating bacterial vaginosis, a known cause for PTB. Low vitamin D levels may be associated with bacterial vaginosis, although no evidence was identified which demonstrated that vitamin D supplementation reduced the risk of having bacterial vaginosis or PTB.There is little evidence regarding vitamin C supplementation, although it does suggest a possible benefit with regard to preterm rupture of membranes; however, this did not appear to reduce rates of PTB.

SUMMARY

Although there is evidence that taking probiotics in pregnancy may reduce the incidence of PTB, it is mainly derived from small, poor quality studies. Vitamin D and vitamin C may have potential benefits, but these remain to be proven. Large randomized controlled trials are needed to more accurately evaluate the potential benefits of these low-cost interventions for reducing PTB and its consequences.

Favorable effects of vitamin D supplementation on pregnancy outcomes in gestational diabetes: a double blind randomized controlled clinical trial

Gestational diabetes mellitus (GDM) has been recognized as a significant risk factor for unfavorable pregnancy outcomes. Prevalence of vitamin D deficiency is highly prevalent among women with GDM. This study was designed to assess the effect of vitamin D supplementation on pregnancy outcomes of pregnant women with GDM who were not on oral hypoglycemic agents. This randomized controlled clinical trial was performed among 45 pregnant women diagnosed with GDM at 24-28 weeks' gestation. Subjects were randomly assigned to consume either vitamin D supplements (cholecalciferol) or placebo. Individuals in the vitamin D group (n=22) received 50 000 IU vitamin D3 pearl 2 times during the study: at study baseline and day 21 of intervention and those in placebo group (n=23) received 2 placebos at the mentioned times. Fasting blood samples were taken at baseline to measure fasting plasma glucose. Participants underwent a 3-h oral glucose tolerance tests (OGTT) and the blood samples were collected at time 60, 120, and 180 min to measure plasma glucose levels. Newborn's weight, height, head circumference, Apgar score, and hyperbilirubinemia were determined. Taking vitamin D supplements, compared with placebo, resulted in improved pregnancy outcomes; such that those in the vitamin D group had no case of polyhydramnios, while 17.4% of subjects in placebo group had this condition (p=0.04). In addition, newborn's hyperbilirubinemia was significantly lower in vitamin D group than that in placebo group (27.3% vs. 60.9%, p=0.02). In conclusion, vitamin D supplementation for 6 weeks among pregnant women with GDM resulted in decreased maternal polyhydramnios and infant hyperbilirubinemia compared with placebo. Clinical trial registration number www.irct.ir:IRCT201305115623N7.

Serum 25-Hydroxyvitamin D Levels: Variability, Knowledge Gaps, and the Concept of a Desirable Range

Hypovitaminosis D is prevalent worldwide but proportions vary widely between regions, depending on genetic and lifestyle factors, the threshold to define deficiency, and accuracy of 25-hydroxyvitamin D (25OHD) assays used. Latitude, pollution, concealing clothing, sun exposure, gender, dietary habits, and lack of government regulation account for up to 50% in variations in serum 25OHD levels, whereas genetic polymorphisms in the vitamin D pathway account for less than 5%. Organizations/societies have developed guidelines for recommended desirable 25OHD levels and vitamin D doses to reach them, but their applicability across age groups and populations are still debated. This article and the accompanying online Supporting Information highlight sources of variations in circulating 25OHD levels, uncertainties and knowledge gaps, and analytical problems facing 25OHD assays, while keeping efficacy and safety data as the dominant factors when defining a desirable range for 25OHD levels. We propose a desirable range of 20 to 40 ng/mL (50 to 100 nmol/L), provided precise and accurate assays are used. Although slightly lower levels, 15 to 20 ng/mL, may be sufficient for some infants and adults, higher levels, 40 to 60 ng/mL, may still be safe. This desirable range allows physicians to tailor treatment while taking season, lifestyle, vitamin D intake, and other sources of variation into account. We reserve 25OHD measurements for at-risk patients, defined by disease or lifestyle, and the use of 25OHD assays calibrated against the recommended international standards. Most target groups reach desirable target levels by a daily intake of 400 to 600 IU for children and 800 IU for adults. A total daily allowance of vitamin D of up to 1000 IU in the pediatric age groups, and up to 2000 IU in adults, tailored to an individual patient risk profile, is probably safe over long durations. Additional data are needed to validate the proposed range and vitamin D doses, especially in children, pregnant women, and non-white populations.