Maternal plasma 25-hydroxyvitamin D concentrations and the risk for gestational diabetes mellitus

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 gestational outcomes.

OBJECTIVES

To examine whether 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 (31 October 2011), the International Clinical Trials Registry Platform (ICTRP) (31 October 2011), the Networked Digital Library of Theses and Dissertations (28 October 2011) and also contacted relevant organisations (8 April 2011).

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.

MAIN RESULTS

The search strategy identified 34 potentially eligible references. We included six trials assessing a total of 1023 women, excluded eight studies, and 10 studies are still ongoing. Five trials involving 623 women compared the effects of vitamin D alone versus no supplementation/placebo and one trial with 400 women compared the effects of vitamin D and calcium versus no supplementation.Only one trial with 400 women reported on pre-eclampsia: women who received 1200 IU vitamin D along with 375 mg of elemental calcium per day were as likely to develop pre-eclampsia as women who received no supplementation (average risk ratio (RR) 0.67; 95% confidence interval (CI) 0.33 to 1.35). Data from four trials involving 414 women consistently show that women who received vitamin D supplements had higher concentrations of vitamin D in serum at term than those women who received no intervention or a placebo; however the magnitude of the response was highly heterogenous. Data from three trials involving 463 women suggest that women who receive vitamin D supplements during pregnancy less frequently had a baby with a birthweight below 2500 grams than those women receiving no treatment or placebo; statistical significance was borderline (RR 0.48; 95% CI 0.23 to 1.01).In terms of other conditions, there were no significant differences in adverse side effects including nephritic syndrome (RR 0.17; 95% CI 0.01 to 4.06; one trial, 135 women); stillbirths (RR 0.17; 95% CI 0.01 to 4.06; one trial, 135 women) or neonatal deaths (RR 0.17; 95% CI 0.01 to 4.06; one trial, 135 women) between women who received vitamin D supplements in comparison with women who received no treatment or placebo. No studies reported on preterm birth, maternal death, admission to neonatal intensive care unit/special nursery or Apgar scores.

AUTHORS' CONCLUSIONS

Vitamin D supplementation in a single or continued dose during pregnancy increases serum vitamin D concentrations as measured by 25-hydroxyvitamin D at term. The clinical significance of this finding and the potential use of this intervention as a part of routine antenatal care are yet to be determined as the number of high quality trials and outcomes reported is too limited to draw conclusions on its usefulness and safety. Further rigorous randomised trials are required to evaluate the role of vitamin D supplementation in pregnancy.

Gestational Diabetes

Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and is strongly related to subsequent risk of type 2 diabetes. The epidemics of obesity and diabetes and the increasing incidence of GDM in recent years highlight the importance of preventing GDM among women at high risk to avoid the associated short- and long-term adverse health outcomes for both mothers and their offspring. Indeed, women may be more likely to adopt healthy lifestyle habits during pregnancy and maintain these habits into the postpartum period. Although there is substantial evidence that targeting at-risk groups for type 2 diabetes prevention is effective if lifestyle changes are made, relatively little attention has been paid to the prevention of GDM. Therefore, the objective of this article is to review the scientific evidence regarding the association between modifiable risk factors and GDM; discuss how lifestyle interventions, including weight management through diet and exercise could be successful in reducing the risk for GDM; and provide recommendations for future lifestyle intervention programs with a focus on translation and dissemination of research findings.

First-trimester maternal vitamin D status and risk for gestational diabetes (GDM) a nested case-control study

BACKGROUND

Vitamin D deficiency may contribute to impaired glucose metabolism. There are sparse data regarding vitamin D and the development of gestational diabetes (GDM). The objective of this study was to assess if first-trimester vitamin D deficiency is more prevalent in women later diagnosed with GDM compared with women with uncomplicated pregnancies.

METHODS

We conducted a nested case-control study of pregnant women who had previously given blood for routine genetic multiple marker screening and subsequently delivered at a tertiary hospital between November 2004 and July 2009. From an overall cohort of 4225 women, 60 cases of GDM were matched by race/ethnicity with 120 women delivering at term (≥37 weeks) with uncomplicated pregnancies. Banked maternal serum was used to measure maternal 25-hydroxyvitamin D [25(OH)D].

RESULTS

The prevalence of first-trimester maternal vitamin D deficiency (defined as 25(OH)D < 50 nmol/L) was comparable among women with GDM compared with controls (5/60 vs 8/120, p = 0.90). The median 25(OH)D level for all subjects was 89 nmol/L (interquartile range, 73-106 nmol/L). Seventy three percent (117/160) of the cohort had 25(OH)D levels ≥75 nmol/L.

CONCLUSIONS

In a cohort of pregnant women with mostly sufficient levels of serum 25(OH)D, vitamin D deficiency was not associated with GDM. Further studies are warranted with larger cohorts, especially in populations with lower levels of vitamin D.

Effects of a single post-partum injection of a high dose of vitamin D on glucose tolerance and insulin resistance in mothers with first-time gestational diabetes mellitus

AIM

This study was performed to determine the effect of a single, large, intramuscular injection of vitamin D post-partum on glucose tolerance and insulin resistance in women with gestational diabetes.

METHODS

Forty-five participants in a randomized controlled trial on gestational diabetes mellitus were divided into an intervention group and a control group. Only subjects in the intervention group received one intramuscular injection of 300,000 IU of vitamin D3. HbA(1c), serum 25-hydroxyvitamin D3, fasting insulin and blood glucose, C-peptide, homeostasis model assessment insulin resistance index (HOMA-IR), β-cell function, insulin sensitivity and the Quantitative Insulin Sensitivity Check Index (QUICKI) were measured at baseline and after 3 months of intervention.

RESULTS

Approximately 80% of the mothers had a degree of vitamin D deficiency. Post-intervention, this was found in 4.2 and 71.4% in the intervention and control groups, respectively. The medians of HOMA-IR indices before and after intervention were 0.6 and 0.5 (P = 0.7), respectively, in subjects in the intervention group, and 0.5 and 0.9 (P = 0.01) in subjects in the control group. The mean of the QUICKI fell only in the control group (P = 0.008). In the control group, β-cell function increased by ~8% (P = 0.01) and insulin sensitivity decreased after 3 months (P = 0.002). Post-intervention, the median C-peptide decreased in the intervention group and increased in the control group, but the change was significant only in the control group (P = 0.03).

CONCLUSIONS

A single injection of 300,000 IU of vitamin D3 achieves a 3-month serum 25-hydroxyvitamin D range of 50-80 nmol/l and is an efficient, effective and safe procedure for improving the vitamin status and indices of insulin resistance in mothers with gestational diabetes after delivery.

Physical activity and dietary behaviors associated with weight gain and impaired glucose tolerance among pregnant Latinas

Pregnancy has been proposed as a critical period for the development of subsequent maternal overweight and/or obesity. Excessive gestational weight gain is, in turn, associated with maternal complications such as cesarean delivery, hypertension, preeclampsia, impaired glucose tolerance, and gestational diabetes mellitus. Although there is substantial evidence that targeting at-risk groups for type 2 diabetes prevention is effective if lifestyle changes are made, relatively little attention has been paid to the prevention of excessive gestational weight gain and impaired glucose tolerance during pregnancy. Latinos are the largest minority group in the United States, with the highest birth and immigration rates of any minority group and are disproportionately affected by overweight and obesity. However, due to cultural factors, socioeconomic factors, and language barriers, Latinos have had limited access to public health interventions that promote healthy lifestyles. Therefore, the objective of this article is to review the scientific evidence regarding the association between physical activity, dietary behaviors, and gestational weight gain and impaired glucose tolerance among Latinas. A second objective is to discuss how lifestyle interventions including weight management through diet and exercise could be successful in reducing the risk of excessive gestational weight gain and gestational diabetes mellitus. Finally, recommendations are provided for future lifestyle intervention programs in this population with a focus on translation and dissemination of research findings.

Inadequate vitamin D status in pregnancy: evidence for supplementation

The role of vitamin D in maintaining a healthy pregnancy has seen emerging interest among clinicians and researchers in recent years. The functions of this hormone are widespread and complex, and during pregnancy and breastfeeding it facilitates crucial transfer of calcium from mother to child for skeletal development. Aside from the role of vitamin D in bone development and health, a myriad of other physiological actions are now known, and it is hypothesized that maternal deficiency may increase susceptibility to adverse pregnancy events during pregnancy such as pre-eclampsia. The role of vitamin D in pregnancy and breastfeeding is summarized and applied to the knowledge from studies associating vitamin D deficiency with a range of adverse pregnancy outcomes, including pre-eclampsia and childhood asthma. Current clinical guidelines for vitamin D supplementation in pregnancy are discussed in the context of the available evidence. The need for robust randomized controlled trials to address areas of existing uncertainty is highlighted.

Calcitriol inhibits interleukin-10 expression in cultured human trophoblasts under normal and inflammatory conditions

Preeclampsia is associated with systemic inflammation and increased expression of placental Th1-cytokines. IL-10 and calcitriol inhibit proinflammatory cytokines expression in human placenta helping to fetal allograft toleration. Regulation of placental IL-10 by calcitriol and Th-1 cytokines has not yet been fully elucidated. Since it is believed that calcitriol promotes a shift from a Th1- to a Th2 profile, we hypothesized that it would stimulate IL-10 in a normal and an inflammatory scenario to conjointly restrain inflammation. Therefore, we investigated calcitriol effects upon IL-10 expression in cultured human trophoblasts obtained from normal (NT) and preeclamptic (PE) pregnancies. Similar studies in the presence of TNF-α (as an inflammatory stressor) were also performed. Calcitriol dose-dependently inhibited IL-10 expression in NT, PE and TNF-α-challenged trophoblasts (P<0.05). This effect was prevented by a vitamin D receptor (VDR) antagonist. IL-10 expression was significantly stimulated by TNF-α and IL-1β, inhibited by IFN-γ and was not affected by IL-6. Finally, calcitriol inhibited TNF-α and IL-1β stimulation upon IL-10. In summary, in cultured human trophoblasts, calcitriol down-regulates IL-10 expression under normal as well as under natural and experimental inflammatory conditions. This effect is mediated by the VDR and might involve direct inhibition of TNF-α. In view of these and previous results it seems that in placenta calcitriol suppresses both Th1- and Th2 cytokines while undertakes the anti-inflammatory effects of IL-10 by itself, since both factors exert this task redundantly. The regulation of IL-10 by IFN-γ suggests that this cytokine could be a viable candidate to explain low IL-10 levels in preeclampsia.

Vitamin D, the placenta and pregnancy

Impaired vitamin D status is common to many populations around the world. However, data suggest that this is a particular problem for specific groups such as pregnant women. This has raised important questions concerning the physiological and clinical impact of low vitamin D levels during pregnancy, with implications for classical skeletal functions of vitamin D, as well as its diverse non-classical actions. The current review will discuss this with specific emphasis on the classical calciotropic effects of vitamin D as well as the less well established immunological functions of vitamin D that may influence pregnancy outcome. The review also describes the pathways that are required for metabolism and function of vitamin D, and the various clinical complications that have been linked to impaired vitamin D status during pregnancy.

Effect of dietary and lifestyle factors on the risk of gestational diabetes: review of epidemiologic evidence

Gestational diabetes mellitus (GDM), defined as glucose intolerance with onset or first recognition in pregnancy, is a common pregnancy complication and a growing health concern. GDM has been related to significant short-term and long-term adverse health outcomes for both mothers and offspring. Importantly, this number is increasing with the increasing burden of obesity among women of reproductive age. Collectively, these data highlight the significance of understanding risk factors, in particular modifiable factors, for GDM and of preventing GDM among high-risk populations. Research in the past decade has identified a few diet and lifestyle factors that are associated with GDM risk. This review provides an overview of emerging diet and lifestyle factors that may contribute to the prevention of GDM. It also discusses major methodologic concerns about the available epidemiologic studies of GDM risk factors.

Vitamin D: role in pregnancy and early childhood

Several studies in pregnant women and early childhood suggest that vitamin D deficiency (serum 25-hydroxyvitamin D levels <50 nmol/l) is common in both population groups. Recent recommendations have therefore reviewed the literature regarding the role of vitamin D in pregnant women and in early childhood. The Institute of Medicine, in their most recent assessment in 2010, recommended 600 IU per day in pregnant and lactating women. In 2011, the US Endocrine Task Force on Vitamin D commented that 600 IU per day may not be sufficient to correct vitamin D deficiency in pregnant and lactating women. Their recommendation was 1,500-2,000 IU vitamin D per day in pregnant and lactating women with vitamin D deficiency. For infants, the recommendation from both societies is consistently 400 IU vitamin D per day, and also in children both societies recommend 600 IU vitamin D per day. This review will summarize the scientific basis that led to the most recent recommendations.

Maternal serum 25-hydroxyvitamin D levels at 11(+0) -13(+6) weeks in pregnant women with diabetes mellitus and in those with macrosomic neonates

OBJECTIVE

To investigate whether maternal serum levels of 25-hydroxyvitamin D [25(OH)D] in the first trimester are altered in pregnant women with pre-existing type 2 diabetes, women who subsequently develop gestational diabetes mellitus (GDM) and women who deliver large for gestational age (LGA) neonates compared with normoglycaemic pregnant women who deliver an appropriate for gestational age (AGA) neonate.

DESIGN

Case-control study.

SETTING

Antenatal clinic.

POPULATION

Singleton pregnancies at 11(+0) -13(+6) weeks, including 50 women with type 2 diabetes, 100 women who subsequently developed GDM, 50 nondiabetic women who subsequently delivered LGA neonates and 1000 nondiabetic controls who delivered AGA neonates.

METHODS

Maternal serum total 25(OH)D levels were measured in the four groups of pregnancies. Multiple regression analysis in the controls was used to identify factors among maternal characteristics with a significant contribution to the levels of serum 25(OH)D, so that the values in all cases were expressed as a multiple of the median (MoM) in the controls.

MAIN OUTCOME MEASURES

Comparison of MoM 25(OH)D in the four groups.

RESULTS

In controls, significant independent contributions to the serum level of 25(OH)D were provided by maternal age, body mass index, smoking status, racial origin and season of sampling. The median and interquartile range (IQR) of serum 25(OH)D in the type 2 diabetes group (1.01; IQR, 0.68-1.47 MoM), GDM group (0.93; IQR, 0.67-1.23 MoM) and LGA group (0.97; IQR, 0.67-1.25 MoM) were not significantly different from those in the controls (0.99; IQR, 0.71-1.33 MoM) (overall P = 0.643).

CONCLUSIONS

The first-trimester maternal serum level of 25(OH)D is not altered in women with type 2 diabetes, those who develop GDM or those who deliver LGA neonates.

Vitamin D - roles in women's reproductive health?

In the past few years a growing interest in vitamin D can be observed in the lay and biomedical literature due to findings demonstrating a low vitamin D status in the population. In addition to its importance for the regulation of calcium and phosphorus homeostasis recent epidemiologic studies have observed relationships between low vitamin D levels and multiple disease states. This secosteroid hormone also regulates the expression of a large number of genes in reproductive tissues implicating a role for vitamin D in female reproduction. In this report we summarize the recent evidence that vitamin D status influences female reproductive and pregnancy outcomes. Human and animal data suggest that low vitamin D status is associated with impaired fertility, endometriosis and polycystic ovary syndrome. Evidence from observational studies shows higher rates of preeclampsia, preterm birth, bacterial vaginosis and gestational diabetes in women with low vitamin D levels. However, confirmation of experimental observations establishing an association of vitamin D deficiency with adverse reproductive outcomes by high quality observational and large-scale randomized clinical trials is still lacking. The determination of optimal 25(OH)D3 levels in the reproductive period and the amount of vitamin D supplementation required to achieve those levels for the numerous actions of vitamin D throughout a woman's life would have important public health implications.

First-trimester maternal serum 25-hydroxyvitamin D₃ status and pregnancy outcome

OBJECTIVE

To determine the pregnancy outcome as a function of the first-trimester serum 25-hydroxyvitamin D(3) [25(OH)D] status and to compare the 25(OH)D levels in the first and third trimesters.

METHODS

Pregnant women (n=466) tested for serum 25(OH)D levels during the first trimester were followed up until the end of pregnancy, and the obstetric and neonatal outcomes were compared in reference to the baseline 25(OH)D status. The third-trimester 25(OH)D levels were additionally measured in a subset of women (n=148).

RESULTS

The obstetric and neonatal outcomes did not vary as a function of the first-trimester 25(OH)D status. Neither did the 25(OH)D levels vary as a function of pregnancy outcomes. Overall, the 25(OH)D levels significantly decreased from the first to the third trimester. The first- and third-trimester 25(OH)D levels of samples initially taken during autumn/winter were significantly lower than those that were initially taken during spring/summer. Interestingly, the decrease in 25(OH)D levels during the third trimester was independent of the season of sampling.

CONCLUSION

The pregnancy outcome was independent of the first-trimester 25(OH)D status. Overall, the 25(OH)D levels significantly decreased in the third trimester. More research in this area is warranted.

Micronutrients in pregnancy: current knowledge and unresolved questions

Micronutrient status is increasingly recognized to play an important role in the health and well-being of pregnant women and in the development and long-term health of the offspring. On 26th - 28th February 2009, The Child Health Foundation invited leading experts in this area to a scientific workshop at Obergurgl, Austria to review and critically discuss current knowledge, to identify issues that may need to be addressed in future recommendations, and to highlight priorities and opportunities for future research. This report summarizes updated key conclusions of the workshop with regards to micronutrients' intake and physiological role related to mother, placenta and fetus, as well as relevance for adverse pregnancy and long-term outcomes.

Vitamin D deficiency before bariatric surgery: should supplement intake be routinely prescribed?

BACKGROUND

Before bariatric surgery, we demonstrate a 96% rate of vitamin D deficiency in morbidly obese French patients: should supplement intake be routinely prescribed? We conducted a prospective observational study to demonstrate the prevalence of vitamin D deficiency in morbidly obese patients awaiting bariatric surgery.

METHODS

Clinical and biological data were collected on 50 successive patients.

RESULTS

Data showed vitamin D deficiency in 96% (25-OH vitamin D = 31 ± 13 nmol/l), with a cut-point of 50 nmol/l. Secondary hyperparathyroidism was found in 44% of patients with hypovitaminosis D (parathyroid hormone (PTH), 59 ± 24 pg/ml). Impaired PTH level concerned 89% of this group, considering the cut-point at 30 pg/ml. No significant correlation appeared between vitamin D and calcium or phosphate levels.

CONCLUSIONS

Before surgery, we demonstrated a higher incidence of vitamin D deficiency in morbidly obese French patients as compared to the general population. The incidence was also higher than previous American studies. Screening for hypovitaminosis D may routinely be considered in morbid obesity. Long-term observation is, however, needed to assess the advantages and potential side effects of systematic vitamin D supplements.

Vitamin D status and its predictive factors in pregnancy in 2 Australian populations

BACKGROUND

High prevalence rates of suboptimal vitamin D levels have been observed in women who are not considered 'at risk'. The effect of behavioural factors such as sun exposure, attire, sunscreen use and vitamin D supplementation on vitamin D levels in pregnancy is unknown.

AIM

To determine prevalence and predictive factors of suboptimal vitamin D levels in 2 antenatal clinics in Australia--Campbelltown, NSW and Canberra, ACT.

METHODS

A cross-sectional study of pregnant women was performed with a survey of demographic and behavioural factors and a mid-pregnancy determination of maternal vitamin D levels.

RESULTS

The prevalence of vitamin D deficiency (≤25 nmol/L) and insufficiency (26-50 nmol/L) was 35% in Canberra (n=100) and 25.7% in Campbelltown (n=101). The majority of participants with suboptimal D levels had vitamin D insufficiency. Among the vitamin D-deficient women, 38% were Caucasian. Skin exposure was the main behavioural determinant of vitamin D level in pregnancy in univariate analysis. Using pooled data ethnicity, season, BMI and use of vitamin D supplements were the main predictive factors of suboptimal vitamin D. Vitamin D supplementation at 500 IU/day was inadequate to prevent insufficiency.

CONCLUSIONS

Behavioural factors were not as predictive as ethnicity, season and BMI. As most participants had one of the predictive risk factors for suboptimal vitamin D, a case could be made for universal supplementation with a higher dose of vitamin D in pregnancy and continued targeted screening of the women at highest risk of vitamin D deficiency.

Oxidative DNA damage in early pregnancy and risk of gestational diabetes mellitus: A pilot study

OBJECTIVES

To examine the association of maternal early pregnancy oxidative stress with risk of gestational diabetes mellitus (GDM).

DESIGN AND METHODS

A pilot prospective, nested case-control study was conducted. Study participants were recruited before 20weeks gestation. Maternal urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of systemic oxidative DNA damage and repair, was measured using competitive immunoassays. Logistic regression was used to calculate odds ratio (OR) and 95% confidence intervals (95%CI).

RESULTS

Elevations in early pregnancy urinary 8-OHdG concentrations were associated with increased GDM risk. After adjusting for confounders, the OR for extreme quartiles (≥8.01 vs. <4.23ng/mg creatinine) of 8-OHdG was 3.79 (95%CI 1.03-14.00). The risk for GDM was highest for overweight women with urine 8-OHdG concentrations ≥8.01ng/mg creatinine (OR=5.36, 95%CI 1.33-21.55) when compared with lean women who had 8-OHdG concentrations <8.01ng/mg creatinine.

CONCLUSIONS

Elevated urine 8-OHdG concentrations in early pregnancy appear to be associated with increased GDM risk.

First-trimester circulating 25-hydroxyvitamin D levels and development of gestational diabetes mellitus

OBJECTIVE

To investigate the association between first-trimester maternal serum levels of 25-hydroxyvitamin D (25-OH-D) as measured by liquid chromatography-tandem mass spectrometry and development of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

We conducted a case-control study involving 248 women in the first-trimester of pregnancy, 90 of whom developed GDM and 158 remained normoglycemic.

RESULTS

Although booking 25-OH-D levels correlated negatively with 2-h glucose post-oral glucose tolerance test and positively with HDL cholesterol, as well as with ethnicity, obesity, and smoking (all P < 0.05), there were no statistically significant differences in baseline maternal mean 25-OH-D levels between those who subsequently developed GDM, 18.9 ng/mL (SD 10.7) and those who remained normoglycemic, 19.0 ng/mL (10.7) (P = 0.874), even after adjustment for possible confounders including sampling month (P = 0.784).

CONCLUSIONS

Our large and well-phenotyped prospective study did not find evidence of an association between first-trimester maternal levels of 25-OH-D and subsequent development of GDM.

VITAMIN D AND HUMAN PREGNANCY

At the end of 2007, Time magazine listed the “benefits of vitamin D” as one of its top 10 medical breakthroughs for that year. Since then there has been a remarkable upsurge of interest in vitamin D, with new research advances seemingly published on a weekly basis. In particular, there has been increasing awareness of the variability of vitamin D status in populations across the globe and, significantly, a growing debate about the need for revised parameters for vitamin D supplementation. Although sub-optimal vitamin D is likely to be a widespread problem for 21stcentury societies, it is also clear that some groups are at much greater risk of low vitamin D status. Prominent amongst these are pregnant women and the aim of the following review article will be to discuss this problem in further detail with specific emphasis on its potential physiological and clinical impact.

Review Article: Health benefit of increased serum 25(OH)D levels from oral intake and ultraviolet-B irradiance in the Nordic countries

Aims: A low serum 25-hydroxyvitamin D [25(OH)D] level is a risk factor for many diseases, including musculoskeletal diseases, many types of cancer, cardiovascular diseases, diabetes mellitus, infectious diseases, autoimmune diseases, and brain diseases. This report estimates the reduction in mortality rates for the five Nordic countries for an increase in population mean serum 25-hydroxyvitamin D level to 105 nmol/L. Methods: Serum vitamin D dose—incidence/prognosis relationships can be developed with significant levels of reliability for most vitamin D-sensitive diseases on the basis of ecological, cross-sectional, and observational studies, randomized controlled trials, and meta-analysis of such studies. These dose—response relations are used to estimate the population-wide benefit of raising mean serum 25(OH)D concentration to 105 nmol/L for the five Nordic countries. Results: From this study, the reductions in mortality rates possible by raising population mean serum 25(OH)D levels to 105 nmol/L are: Denmark, 17% (estimated range,11%—24%); Finland, 24% (17%—32%); Iceland, 24% (17%—32%); Norway, 18% (11%—26%); and Sweden, 18% (8%—25%). Conclusions: Reaching these levels would require changes in health policies with respect to solar ultraviolet-B (UVB) irradiance, vitamin D fortification of food, availability of vitamin D and calcium supplements, and attitude toward use of UVB lamps. Adverse effects of oral vitamin D intake are limited, and those from UVB irradiance are minor compared with the benefits.

Association of modifiable and nonmodifiable factors with vitamin D status in pregnant women and neonates in Oakland, CA

There is little information on the contribution of modifiable vs nonmodifiable factors to maternal and neonatal vitamin D status in temperate regions of the United States. The purpose of this cross-sectional observation study conducted between December 2006 and February 2008 was to identify associations between observed and measured maternal characteristics and vitamin D status at term in pregnant women and their infants in a multiethnic community in Oakland, CA. Two hundred seventy-five pregnant women aged 18 to 45 years and carrying a singleton fetus were recruited and data from 210 mother-infant pairs were included in analyses. Analysis of covariance identified predictors of maternal and cord serum 25-hydroxyvitamin D [25(OH)D] in a multivariate model considering vitamin D intake, lifestyle factors, and skin pigmentation. Maternal serum 25(OH)D was significantly associated with season of delivery (P=0.0002), average daily D intake (P=0.0008), right upper inner arm pigmentation (P=0.0035), and maternal pre- or early-pregnancy body mass index (calculated as kg/m²) (P=0.0207). The same factors were significant for cord serum 25(OH)D, which was highly correlated with maternal serum 25(OH)D (r=0.79; P<0.0001). During the year, 54% of mothers and 90% of neonates had 25(OH)D <30 ng/mL (<75 nmol/L). Of women taking daily prenatal vitamin/mineral supplements (400 IU vitamin D), 50.7% had serum 25(OH)D <30 ng/mL (<75 nmol/L). In conclusion, 25(OH)D <30 ng/mL (<75 nmol/L) was prevalent in mothers and neonates across racial groups and seasons, and vitamin D status was associated with both modifiable and nonmodifiable risk factors.

Global maternal early pregnancy peripheral blood mRNA and miRNA expression profiles according to plasma 25-hydroxyvitamin D concentrations

OBJECTIVE

We investigated associations of early pregnancy maternal vitamin D concentrations with differential gene expression and post-transcription regulation.

METHOD

Plasma 25-hydroxyvitamin D (25[OH]D) was measured among participants of a nested case-control study. Participants with low (<25.5 ng/ml) and high (≥31.7 ng/ml) 25[OH]D were identified among controls. Peripheral blood messenger RNA (mRNA) (N = 21) and microRNA (miRNA) (N = 13) expression studies were conducted among participants with low and high 25[OH]D concentrations. Differential expression between low/high groups were evaluated using Student's t-test, fold change, and SAM comparisons. We further investigated functions and functional relationships of differentially expressed mRNAs and targets of differentially expressed miRNAs.

RESULTS

Three hundred and five genes (299 upregulated and 6 downregulated) and 11 miRNAs (10 downregulated and 1 upregulated) were differentially expressed among participants with low 25[OH]D compared with those who had high 25[OH]D. Genes that participate in a wide range of cellular functions, including organ and system development (e.g. angiogenesis), inflammation and metabolic processes (e.g. carbohydrate/lipid metabolism), as well as miRNAs that target these genes were differentially expressed among women with low 25[OH]D compared with those with high 25[OH]D.

CONCLUSION

Early pregnancy plasma 25[OH]D concentrations are associated with maternal peripheral blood gene expression and post-transcription regulation.

Vitamin D effects on pregnancy and the placenta

Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.

Prevalence and predictors of vitamin D insufficiency in women of reproductive age living in northern latitude

OBJECTIVE

This study assessed the prevalence of vitamin D deficiency (serum 25-hydroxyvitamin D (25OHD) ≤ 50 nmol/l) and insufficiency (serum 25OHD 51-74 nmol/l) during summer and the predictors of serum 25OHD in young women of reproductive age.

DESIGN

Cross-sectional study.

METHODS

Between May and September 2006, 153 healthy, ambulatory and essentially Caucasian women, aged 18-41 years, were recruited. Serum 25OHD and parathyroid hormone (PTH) levels were measured, and questionnaires were evaluated.

RESULTS

About 3.9% of women had serum 25OHD ≤ 50 nmol/l with an additional 26.8% in the insufficient range. Most women (56.9%) had their blood sampled in September. Month of blood collection significantly influenced serum 25OHD. Body mass index (BMI) was inversely associated with serum 25OHD, while traveling to a warmer climate during winter/spring and using oral contraceptive pills (OCP) were associated with higher serum 25OHD. Sunscreen was used by 77.8% of women, but only 3.3% reported consuming vitamin D supplements. BMI, serum PTH, travel to a warmer climate, and OCP use were independently and significantly associated with serum 25OHD, after adjustment for the month of sampling, and explained 40% of the variance in serum 25OHD.

CONCLUSIONS

In Canada, the prevalence of vitamin D insufficiency is relatively high (30%) during summer in healthy women of reproductive age. Given the expected decrease in serum 25OHD during winter and the low consumption of vitamin D supplements, a high prevalence of vitamin D deficiency and insufficiency is to be anticipated during winter, except maybe for those traveling to a warmer climate.

Vitamin D deficiency is common among pregnant women in rural Victoria

There is increasing evidence to implicate vitamin D deficiency in a variety of diseases. Previous advice has been to screen high-risk pregnant women. This study shows that, despite abundant sunshine and latitude consistent with year-long vitamin D synthesis, 65.5% of a largely low-risk antenatal population in rural Victoria have insufficient vitamin D. Over 5.0% of women have vitamin D levels that pose a significant neonatal and adult health risk. These findings support routine antenatal testing of vitamin D levels.

Vitamin D effects on pregnancy and the placenta

Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.

Prognostic value of follicular fluid 25-OH vitamin D and glucose levels in the IVF outcome

OBJECTIVES

The aim of the present study was to measure serum and follicular fluid 25-OH vitamin D and glucose levels in women who underwent IVF-ET treatment and to further investigate whether the circulating 25-OH vitamin D and glucose levels correlate with IVF success.

METHODS

This prospective observational study included 101 consecutive women who underwent 101 IVF-ICSI ovarian stimulation cycles and were allocated to one of the three groups according to their follicular fluid 25-OH vitamin D concentrations. Group A (n = 31) with less than 20 ng/ml, group B (n = 49) with vitamin levels between 20.1 and 30 ng/ml and group C (n = 21) with more than 30 ng/ml vitamin concentration.

RESULTS

Follicular fluid vitamin levels significantly correlated with the quality of embryos in total (r = -0.27, p = 0.027), while the quality of embryos of group C were of lower quality as compared to those of groups A and B (p = 0.009). Follicular fluid glucose levels were lower in women of group C as compared to the respective levels of groups A and B (p = 0.003). Clinical pregnancy rate demonstrated in 14.5% in women of group C and 32.3% and 32.7% in groups A and B, respectively (p = 0.047).

CONCLUSION

The data suggests that excess serum and follicular fluid vitamin levels in combination with decreased follicular fluid glucose levels have a detrimental impact on the IVF outcome.

Vitamin D, blood pressure, and African Americans: toward a unifying hypothesis

Vitamin D deficiency has increasingly been recognized in the general population and especially in African Americans whose deep skin pigmentation makes vitamin D photosynthesis inefficient. Over the last decade there has been increasing interest in the role that vitamin D deficiency may play in BP modulation because many epidemiologic studies have shown an inverse association between serum vitamin D concentration and BP. There is a high prevalence of vitamin D deficiency in African Americans who also have an increased susceptibility to develop hypertension and its consequences. This paper will review the circumstances leading to vitamin D deficiency in the African American population and will also discuss how vitamin D deficiency can affect the renin-angiotensin system, free radical production, inflammatory processes, and carbohydrate tolerance that in turn influence vascular endothelial function and vascular structure producing increased vascular resistance. It will speculate that the presence of vitamin D deficiency throughout life from its earliest phases may adversely affect the microvasculature in African Americans, thereby playing a major role in the genesis and maintenance of hypertension.

Vitamin D and multiple sclerosis

The hypothesis that adequate vitamin D nutrition can contribute to the prevention of multiple sclerosis (MS) was originally proposed to explain the geographical distribution of MS, but only recently has the relation between various measures of vitamin D (eg, sun exposure, dietary sources, and serum concentrations of 25-hydroxyvitamin D) and risk of developing MS been rigorously investigated. Overall, the results of these studies support a protective effect of vitamin D, but there are uncertainties and many unanswered questions, including how vitamin D exerts a protective effect, how genetic variations modify the effect, and whether vitamin D can influence the course of MS progression.

Vitamin D and diabetes

Type 1 (T1D) and type 2 (T2D) diabetes are considered multifactorial diseases in which both genetic predisposition and environmental factors participate in their development. Many cellular, preclinical, and observational studies support a role for vitamin D in the pathogenesis of both types of diabetes including: (1) T1D and T2D patients have a higher incidence of hypovitaminosis D; (2) pancreatic tissue (more specifically the insulin-producing beta-cells) as well as numerous cell types of the immune system express the vitamin D receptor (VDR) and vitamin D-binding protein (DBP); and (3) some allelic variations in genes involved in vitamin D metabolism and VDR are associated with glucose (in)tolerance, insulin secretion, and sensitivity, as well as inflammation. Moreover, pharmacologic doses of 1,25-dihydroxyvitamin D (1,25(OH)(2)D), the active form of vitamin D, prevent insulitis and T1D in nonobese diabetic (NOD) mice and other models of T1D, possibly by immune modulation as well as by direct effects on beta-cell function. In T2D, vitamin D supplementation can increase insulin sensitivity and decrease inflammation. This article reviews the role of vitamin D in the pathogenesis of T1D and T2D, focusing on the therapeutic potential for vitamin D in the prevention/intervention of T1D and T2D as well as its complications.

Maternal serum 25-hydroxyvitamin D concentrations are associated with small-for-gestational age births in white women

Maternal vitamin D deficiency has been associated with numerous adverse health outcomes, but its association with fetal growth restriction remains uncertain. We sought to elucidate the association between maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations in early pregnancy and the risk of small-for-gestational age birth (SGA) and explore the association between maternal single nucleotide polymorphisms (SNP) in the vitamin D receptor (VDR) gene and the risk of SGA. We conducted a nested case-control study of nulliparous pregnant women with singleton pregnancies who delivered SGA infants (n = 77 white and n = 34 black) or non-SGA infants (n = 196 white and n = 105 black). Women were followed from <16 wk gestation to delivery. Women's banked sera at <22 wk were newly measured for 25(OH)D and DNA extracted for VDR genotyping. SGA was defined as live-born infants that were <10th percentile of birth weight according to nomograms based on gender and gestational age. After confounder adjustment, there was a U-shaped relation between serum 25(OH)D and risk of SGA among white mothers, with the lowest risk from 60 to 80 nmol/L. Compared with serum 25(OH)D 37.5-75 nmol/L, SGA odds ratios (95% CI) for levels <37.5 and >75 nmol/L were 7.5 (1.8, 31.9) and 2.1 (1.2, 3.8), respectively. There was no relation between 25(OH)D and SGA risk among black mothers. One SNP in the VDR gene among white women and 3 SNP in black women were significantly associated with SGA. Our results suggest that vitamin D has a complex relation with fetal growth that may vary by race.

Vitamin D may be a link to black-white disparities in adverse birth outcomes

In the United States, significant, intractable disparities exist in rates of major pregnancy outcomes between non-Hispanic black and non-Hispanic white women. A previously unexplored candidate influence on the black-white disparity in adverse birth outcomes is maternal vitamin D status. This review summarizes the evidence relating maternal vitamin D to preeclampsia, spontaneous preterm birth, gestational diabetes, and fetal growth restriction, and addresses gaps in our understanding of the contribution of vitamin D to the intractable black-white disparity in these conditions. The literature reviewed highlights strong biologic plausibility of role for vitamin D in the pathophysiology of these poor pregnancy outcomes. Data also suggest that maternal vitamin D deficiency may increase the risk of preeclampsia and fetal growth restriction. Less research has been done in support of relations with spontaneous preterm birth and gestational diabetes, and fetal and infant survival have rarely been studied. Few trials of vitamin D supplementation have been conducted in pregnant women with adequate power to test effects on birth outcomes. Importantly, black pregnant women have rarely been studied in vitamin D-birth outcomes research. Although vitamin D is a promising candidate influence on black-white disparities in preeclampsia, spontaneous preterm birth, fetal growth restriction, and gestational diabetes, these associations require further study in large samples of black US women. Because vitamin D deficiency is widespread and black-white disparities in pregnancy outcomes and infant survival have been resistant to previous interventions, research to test vitamin D as a causal factor is of major public health significance.

TARGET AUDIENCE

Obstetricians & Gynecologist, Family Physicians.

LEARNING OBJECTIVES

After completion of this educational activity, the reader will be able to appreciate risk factors for inadequate vitamin D status. Understand the basic aspects of vitamin D metabolism. Become aware of recent literature linking inadequate vitamin D status and adverse pregnancy outcomes such as preeclampsia and preterm birth.

Environmental factors and their timing in adult-onset multiple sclerosis

Multiple sclerosis (MS) is a common, complex neurological disease. Epidemiological data implicate both genetic and environmental factors in the etiology of MS, with various factors interacting with one another. Environmental exposures might occur long before the disease becomes clinically evident, as suggested by the wide range in onset age. In this Review, we examine the key time periods during which the environment might contribute to MS susceptibility, as well as the potential environmental factors involved. Understanding the nature of environmental influences in MS is highly relevant to the development of public health measures that are aimed at preventing this debilitating disease.

Understanding the role of diet in type 2 diabetes prevention

The number of people with type 2 diabetes is increasing at an alarming rate. Almost 4% of the UK population currently have diagnosed diabetes. Non-modifiable risk factors for diabetes include genetic predisposition, some black and ethnic minority groups and increasing age. Type 2 diabetes, (formally known as maturity onset diabetes), used to be a condition affecting adults only, although due to the increasing levels of obesity, it is now being diagnosed in young people and children. A healthy diet and lifestyle can help to prevent or delay the development of type 2 diabetes. In particular, strategies to reduce obesity will have a beneficial effect on the prevalence of type 2 diabetes, as excess adiposity (particularly central adiposity) is a strong risk factor for the condition. Dietary measures to reduce the risk of coronary heart disease will also help prevent diabetes. Diets low in fat (particularly saturated fat), and high in fibre and complex carbohydrates are effective in reducing the risk of developing diabetes. Good quality evidence from trials is required to determine the role of specific micronutrients in diabetes prevention.

Vitamin D deficiency during pregnancy may impair maternal and fetal outcomes

Over the past decade, new evidence has shown that vitamin D deficiency may contribute to the risk of developing a wide range of common chronic diseases that are different from the classic action on calcium and bone homeostasis. Acting through the vitamin D receptor, vitamin D can produce a wide array of favorable biological effects via genomic, non-genomic or intracrine mechanisms and, therefore, contributes to the improvement of human health in humans. We hypothesize that some of these effects may be even more critical during pregnancy. The focus of this paper is to review the data on the classic and non-classic actions of vitamin D with regards to pregnancy. It appears that vitamin D insufficiency during pregnancy is potentially associated with increased risk of preeclampsia, insulin resistance and gestational diabetes mellitus. Furthermore, experimental data also anticipate that vitamin D sufficiency is critical for fetal development, and especially for fetal brain development and immunological functions. Vitamin D deficiency during pregnancy may, therefore, not only impair maternal skeletal preservation and fetal skeletal formation but also be vital to the fetal "imprinting" that may affect chronic disease susceptibility soon after birth as well as later in life.