Vitamin D and gestational diabetes mellitus

The Effect of Vitamin D3 Intervention on the Association Among Vitamin D3, Adiponectin, and Body Mass Index in Pregnant Women With Gestational Diabetes

INTRODUCTION

Vitamin D3 (VD3) deficiency is a strong predictor of gestational diabetes. Therefore, VD3 supplementation during the antenatal period could prevent the development of gestational diabetes via its effects on insulin secretion, insulin sensitivity, body mass index (BMI), and adiponectin production.

OBJECTIVES

To observe the effect of VD3 supplementation on adiponectin and BMI and to explore the effect of VD3 supplementation on the association among VD3, adiponectin, and BMI in pregnant women with gestational diabetes.

METHODS

A randomized control trial was performed after receiving consent at Postgraduate Medical Institute, Lahore. Subjects at 20-26 weeks of gestation with gestational diabetes and with a deficiency/insufficiency of VD3 were included. The study excluded those who were smokers, had multiple pregnancies, or had other gestational complications. Subjects were categorized into interventional (VD3 supplementation) and control groups. The institutional ethical committee approved the study. Serum samples were used for enzyme-linked immunosorbent assay estimation of VD3 and adiponectin levels. Statistical Product and Service Solutions (SPSS) (IBM SPSS Statistics for Windows, Version 21.0, Armonk, NY) software was used to analyze data. Student t-tests were applied to compare quantitative variables, and Chi-square tests were utilized to compare qualitative variables. Pearson's correlation and linear regressions were performed to explore the association. At a 95% confidence interval, a p-value of ≤0.05 was taken as significant.

RESULTS

With an increase in serum VD3 levels, a decrease in serum adiponectin level was observed in pregnant women with gestational diabetes (interventional group: r = -0.088, p = 0.74); however, after the intervention of VD3 supplementation in the same subjects, an increase in serum adiponectin level was noted with an increase in VD3 (interventional group: r = 0.273, p = 0.28). A significant direct relationship was found between BMI and adiponectin in the same study population (interventional group: r = 0.7, p = 0.001). Interestingly, after the intervention, BMI tends to be less likely to increase adiponectin levels (interventional group: r = 0.09, p = 0.73). Moreover, an inverse association was exhibited between BMI and VD3 levels in all the study groups before intervention (control group: r = -0.07, p = 0.78; interventional group: r = -0.035, p = 0.89) and after intervention (interventional group: r = -0.12, p = 0.65), except in the control group after the intervention span, where BMI mildly raises the VD3 levels (r = -0.12, p = 0.65).

CONCLUSION

BMI increases with an increase in serum adiponectin levels in gestational diabetic women, but after VD3 supplementation, BMI was less likely to influence adiponectin. Also, with an increase in BMI, a decrease in the VD3 in all study groups was observed except in the control group after VD3 supplementation.

Effect of third trimester maternal vitamin D levels on placental weight to birth weight ratio in uncomplicated pregnancies

OBJECTIVES

Vitamin D has critical role for the fetal and placental development. Today, placental weight (PW), fetal birth weight (BW), and the PW/BW ratio are used as markers of fetal development. The aim of this study is to evaluate the relationship between vitamin D levels and these markers in uncomplicated pregnancies.

METHODS

This study included 108 women with uncomplicated pregnancies, defined as full-term and healthy pregnancies without perinatal complications. Vitamin D levels <12 ng/mL were classified as deficient, 12-20 ng/mL as insufficient, and >20 ng/mL as normal. Postnatal BW and PW were compared according to maternal serum vitamin D levels.

RESULTS

Maternal age, maternal height, maternal weight, body mass index, nulliparity, gestational age at delivery, mode of delivery, and fetal gender were similar between groups. Postnatal BW, PW, fetal height at birth, and fetal head circumference parameters were similar between the groups. The PW/BW ratio was 21.77±2.20 in the vitamin D deficient group, 21.20±2.40 in the insufficient group, and 19.98±2.37 in the normal group (p=0.012). In addition, there was a significant negative correlation between vitamin D level and the PW/BW ratio (p=0.012, r=0.031).

CONCLUSIONS

Our results indicated that PW/BW ratio which is the marker for prediction adverse perinatal outcomes were significantly increased in the presence of vitamin D deficiency and insufficiency.

Effects of vitamin D on insulin resistance and fasting blood glucose in pregnant women with insufficient or deficient vitamin D: a randomized, placebo-controlled trial

BACKGROUND

Gestational diabetes is one of the most common metabolic disorders during pregnancy. Some studies have reported the effect of vitamin D deficiency on the incidence of this disorder. Therefore, the purpose of the present study was to determine the effect of vitamin D supplementation on fasting blood glucose (FBG) levels, fasting blood insulin (FBI) levels and insulin resistance index (HOMA-IR) (primary outcomes) and symptoms of depression, musculoskeletal pain, frequency of gestational diabetes and the frequency of abortion (secondary outcomes).

METHODS

In this triple-blind randomized controlled trial, 88 pregnant women at 8-10 weeks of pregnancy who had the vitamin D of less than 30 ng/ml were randomly assigned to the vitamin D group (n = 44) and control group (n = 44) using block randomization. The vitamin D group received 4,000 units of vitamin D tablets daily and the control group received placebo tablets for 18 weeks. Independent t-test, Mann-Whitney U and ANCOVA tests were used to analyze the data.

RESULTS

After the intervention, there was no statistically significant difference between the two groups in terms of FBG (P = 0.850), FBI (P = 0.353), HOMA-IR (P = 0.632), mean score of depressive symptoms (P = 0.505), frequency of gestational diabetes (P = 0.187) and frequency of abortion (P = 1.000) and there was only a difference in terms of serum vitamin D level (P = 0.016) and musculoskeletal pain including knee pain (P = 0.025), ankle pain (P < 0.001) and leg pain (P < 0.001).

CONCLUSION

Vitamin D could improve the musculoskeletal pain in pregnant women but couldn't decrease FBG, FBI, HOMA-IR, depression symptoms score, incidence of GDM and abortion.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials (IRCT): IRCT20120718010324N59. Date of registration: 4/11/2020. URL: https://en.irct.ir/user/trial/50973/view ; Date of first registration: 21/11/2020.

Association between vitamin D levels in early pregnancy and gestational diabetes mellitus: A systematic review and meta-analysis

Background

This meta-analysis aimed to pool all the available data to provide a well-powered assessment of the role of maternal Vitamin D levels in developing gestational diabetes mellitus (GDM) because already published studies evaluating this association are small in sample size and yielded conflicting findings.

Material and Methods

A systematic review and meta-analysis of observational studies was performed. We searched electronic databases (PubMed and Cochrane Central) from inception to April 2021 for published and unpublished observational studies that determined the association between the reduction of Vitamin D levels and the risk of developing GDM in pregnant women. Results from studies were pooled as mean ± standard deviation (SD) and odds ratios (OR) using the random-effects model.

Results

Forty-four studies, consisting of 37,838 pregnant women were included in this meta-analysis. Dichotomous studies showed a significant association between maternal Vitamin D deficiency and increased risk of GDM (OR = 1.38; 95% confidence interval [CI] = 1.21-1.57; P < 0.00001). Studies with continuous data also showed a significant association between maternal Vitamin D deficiency and the risk of developing GDM (weighted mean difference (WMD): -5.14 nmol/L, 95% CI = -6.28 to -4.00; P < 0.00001). Moderate heterogeneity was also detected.

Conclusion

In conclusion, all studies demonstrated that lower levels of maternal serum Vitamin D were associated with a higher risk of developing GDM in pregnancy.

Vitamin D Status and Gestational Diabetes in Russian Pregnant Women in the Period between 2012 and 2021: A Nested Case-Control Study

Several meta-analyses found an association between low maternal serum 25-hydroxyvitamin D (25(OH)D) level and gestational diabetes mellitus (GDM). However, some of them reported significant heterogeneity. We examined the association of serum 25(OH)D concentration measured in the first and in the second halves of pregnancy with the development of GDM in Russian women surveyed in the periods of 2012−2014 and 2018−2021. We conducted a case−control study (including 318 pregnant women) nested on two previous studies. In 2012−2014, a total of 214 women (83 GDM and 131 controls) were enrolled before 15 weeks of gestation and maternal serum 25(OH)D concentrations were measured twice: at 8th−14th week of gestation and simultaneously with two-hour 75 g oral glucose tolerance test (OGTT) at 24th−32nd week of gestation. In the period of 2018−2021, 104 women (56 GDM and 48 controls) were included after OGTT and 25(OH)D concentrations were measured at 24th−32nd week of gestation. Median 25(OH)D levels were 20.0 [15.1−25.7] vs. 20.5 [14.5−27.5] ng/mL (p = 0.565) in GDM and control group in the first half of pregnancy and 25.3 [19.8−33.0] vs. 26.7 [20.8−36.8] ng/mL (p = 0.471) in the second half of pregnancy, respectively. The prevalence rates for vitamin D deficiency (25(OH)D levels < 20 ng/mL) were 49.4% and 45.8% (p = 0.608) in the first half of pregnancy and 26.2% vs. 22.1% (p = 0.516) in the second half of pregnancy in women who developed GDM and in women without GDM, respectively. The frequency of vitamin D supplements intake during pregnancy increased in 2018−2021 compared to 2012−2014 (p = 0.001). However, the third trimester 25(OH)D levels and prevalence of vitamin D deficiency (25.5 vs. 23.1, p = 0.744) did not differ in women examined in the periods of 2012−2014 and 2018−2021. To conclude, there was no association between gestational diabetes risk and maternal 25(OH)D measured both in the first and in the second halves of pregnancy. The increased prevalence of vitamin D supplements intake during pregnancy by 2018−2021 did not lead to higher levels of 25(OH)D.

Vitamin D intake modifies the association of household air pollution exposure with maternal disorders of pregnancy

To date, only three studies have investigated the association of household air pollution (HAP) exposure with pregnancy disorders. The ameliorating role of diet and nutrition in the association has never been explored. We conducted a cross-sectional study among 799 mothers who had recently given singleton birth in the Cape Coast Metropolis, Ghana. Structured questionnaire and semi-quantitative food frequency questionnaire were used to assess HAP exposure (from use of biomass fuels for cooking and garbage burning at home) and vitamin D (vitD) intake, respectively. Multivariable binary logistic regression was used to investigate the association between HAP exposure and pregnancy disorders. HAP exposure due to cooking with biomass fuels and garbage burning at home was associated with two fold (AOR = 2.15; 95% confidence interval [CI]: 1.05, 4.43) and six fold (AOR = 6.35; 95% CI: 2.43, 16.58) increased odds of hypertensive disorders of pregnancy (HDP). For gestational diabetes (GDM), the increased odds were two folds for both exposures but the 95% CI included the null value. Stove stacking was also associated with two folds increased odds of GDM (AOR = 1.83; 95% CI: 0.91, 3.68). In stratified analysis, the odds of HDP and GDM associated with biomass fuels use decreased with increasing vitD intake. All the interaction p values were, however, greater than 0.05. We provide the first evidence on the ameliorating role of vitD intake on the effect of HAP exposure on pregnancy disorders. In LMICs where solid fuel use and garbage burning at home is widespread, health workers should advise mothers during antenatal care visits to increase intake of vitamin D rich foods.

Plasma 25(OH)D Concentrations and Gestational Diabetes Mellitus among Pregnant Women in Taiwan

Vitamin D’s function in the development of gestational diabetes mellitus (GDM) is not consistent in the literature. We examined the association between maternal plasma 25(OH)D concentration and GDM risk. A national cross-sectional study (1497 pregnant women) was conducted between 2017 and 2019 across Taiwan. Blood samples were drawn at recruitment to assess 25(OH)D concentrations, including vitamin D deficiency (VDD) (<20 ng/mL), insufficiency (<32 ng/mL), and sufficiency (≥32 ng/mL). GDM was detected from 24 to 28 weeks of gestation with the results extracted from the antenatal visit records. The prevalence of GDM was 2.9%. Logistic model analysis showed that 25(OH)D concentrations were not significantly associated with the risk of GDM (adjusted odds ratio (AOR) = 0.97, p = 0.144). However, subjects with VDD had a significantly greater risk of GDM (AOR = 2.26, p = 0.041), but not in those with vitamin D insufficiency (AOR = 1.20, p = 0.655). Furthermore, cubic piecewise spline regression was used to explore the relationship between five-unit intervals of 25(OH)D and the predicted probability of GDM. As the proportion of GDM increased for low 25(OH)D concentrations, it decreased at moderate concentrations and increased again at higher concentrations. These findings revealed a nonlinear relationship between 25(OH)D and GDM risk. VDD would be risky for GDM occurrence.

The Association between Maternal Serum Vitamin D Levels and Gestational Diabetes Mellitus among Filipino Patients: A Cross-Sectional Study

Objectives

To determine the association between low maternal serum vitamin D and gestational diabetes mellitus (GDM) among Filipino women in St. Luke’s Medical Center, Quezon City.

Methodology

A cross-sectional study involving pregnant women at outpatient clinics in a tertiary hospital in the Philippines. Simultaneous testing for fasting blood sugar, 75g oral glucose tolerance test and serum vitamin D was done. Participants were classified as GDM versus non-GDM, and normal versus low serum vitamin D. Univariate and multivariate statistics were done to determine relationship between vitamin D and GDM.

Results

Of 211 included women, 198 (93.8%) had low vitamin D levels, and 56 (26.5%) had GDM. Vitamin D was significantly higher in the GDM group (21.0±8.1 vs 18.8±5.3 ng/mL, p=0.0189). The proportion of women with low vitamin D levels was significantly higher among those without GDM (96.1% vs 87.5%, OR=0.28, p=0.029]. After adjusting for age, parity, history of GDM and pre-pregnancy BMI, no significant association was observed (adjusted OR=0.66, p=0.522). No correlation was seen between vitamin D and FBS (r=0.28, p=0.095), 1-hour post-75 g OGTT (r=0.26, p=0.643), and 2-hour post-75 g OGTT (r=0.28, p=0.113).

Conclusion

There was an association found between maternal serum vitamin D level and GDM in the univariate analysis, but none was evident after adjusting for possible confounders. The unanticipated high prevalence of low vitamin D levels among pregnant Filipinos needs to be verified in future studies.

A Vegetable Dietary Pattern Is Associated with Lowered Risk of Gestational Diabetes Mellitus in Chinese Women

BACKGROUND

Identification of modifiable dietary factors, which are involved in the development of gestational diabetes mellitus (GDM), could inform strategies to prevent GDM.

METHODS

We examined the dietary patterns in a Chinese population and evaluated their relationship with GDM risk using a case-control study including 1,464 cases and 8,092 control subjects. Propensity score matching was used to reduce the imbalance of covariates between cases and controls. Dietary patterns were identified using factor analysis while their associations with GDM risk were evaluated using logistic regression models.

RESULTS

A "vegetable" dietary pattern was characterized as the consumption of green leafy vegetables (Chinese little greens and bean seedling), other vegetables (cabbages, carrots, tomatoes, eggplants, potatoes, mushrooms, peppers, bamboo shoots, agarics, and garlic), and bean products (soybean milk, tofu, kidney beans, and cowpea). For every quartile increase in the vegetables factor score during 1 year prior to conception, the first trimester, and the second trimester of pregnancy, the GDM risk lowered by 6% (odds ratio [OR], 0.94; 95% confidence interval [CI], 0.89 to 0.99), 7% (OR, 0.94; 95% CI, 0.88 to 0.99), and 9% (OR, 0.91; 95% CI, 0.86 to 0.96).

CONCLUSION

In conclusion, our study suggests that the vegetable dietary pattern is associated with lower GDM risk; however, the interpretation of the result should with caution due to the limitations in our study, and additional studies are necessary to explore the underlying mechanism of this relationship.

The Effect of Dietary Intake of Vitamin D on Gestational Diabetes Mellitus

Diabetes mellitus (DM) is a growing health issue that has been reaching epidemic proportions in the recent years. Low intake of some nutrients like vitamin D may increase the risk of gestational diabetes mellitus (GDM). This study was to investigate the association between the dietary intake of Vitamin D and GDM among women in the Eastern Region of Saudi Arabia. A case-control study was conducted in a sample of 121 women, among those 72 were with GDM and 49 were controls. Vitamin D was estimated using food frequency questionnaire. Also, the 24-h’s dietary recall was carried out for 3 days to determine the nutrient intake as well as biochemical analysis for blood glucose level. In this study, GDM subjects were consuming significantly more eggs (P = .040). Vitamin D and vitamin C intakes in GDM and control pregnant women were lower than recommended dietary allowances (RDA). It was also found that low-fat milk, full-fat milk, fortified yogurt, and fortified orange juice were significantly associated with GDM (P < 0.05). Saudi women with GDM need a well-organized dietary counseling before, during pregnancy, and after delivery especially for vitamin D sources.

Hypovitaminosis D Is Associated with Some Metabolic Indices in Gestational Diabetes Mellitus

Background

Gestational diabetes mellitus (GDM), a pregnancy complication, is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. Vitamin D deficiency and insufficiency has recently been recognized as a contributing factor to the pathogenesis of GDM, and this link might be associated with hyperglycemia, insulin resistance, and inflammation, which are implicated in GDM.

Objectives

This study aims at investigating the relationship between vitamin D, fasting plasma glucose (FPG), insulin, zinc, ferritin, and high-sensitivity C-reactive protein (CRP) in GDM.

Method

A case-control study in which 80 women attending the antenatal clinic of University College Hospital (UCH), Ibadan, Nigeria, were recruited; the women were grouped into controls (40 nondiabetic pregnant women) and cases (40 pregnant women with GDM). Blood samples were taken at the second trimester, and metabolites were quantified by standard laboratory methods. Student's t test and Pearson correlation were used to compare variables and determine the relationship between variables, respectively.

Results

Results showed significant (p < 0.05) low levels of serum vitamin D and zinc, and significant (p < 0.05) higher levels of FPG and serum insulin, ferritin, and CRP in the GDM group compared to the control group. In the GDM group, a positive weak relationship was observed between vitamin D and zinc (r = 0.18, p < 0.05), while vitamin D was inversely correlated with FPG, serum insulin, ferritin, and CRP (r = -0.23, -0.21, -0.20, -0.46, respectively, p < 0.05).

Conclusion

This study suggests that hypovitaminosis D might be associated with glucose intolerance, insulin insensitivity, and inflammation, which are factors implicated in the development and progression of GDM.

The Role of Vitamin D in the Development of Diabetes Post Gestational Diabetes Mellitus: A Systematic Literature Review

Women diagnosed with gestational diabetes mellitus (GDM) are more likely to later develop diabetes. Evidence from some previous reviews suggests that low vitamin D status during pregnancy increases the risk of developing GDM, but whether vitamin D during pregnancy also influences the risk of diabetes post GDM is less well studied. Thus, the aim of this systematic literature review was to summarize the current available literature on that topic. This review considered observational studies and randomized controlled trials (RCTs). Five databases were searched. The risk of bias of the included studies was assessed. A total of six studies were included: three observational studies and three RCTs. Findings were inconsistent across the six included studies. However, when considering RCTs only, the findings more strongly suggested that vitamin D supplementation during and after pregnancy did not have an influence on markers of diabetes development or diabetes development post GDM. This systematic review highlights inconsistent findings on the associations between vitamin D supplementation or concentration during and after pregnancy and markers of diabetes development or diabetes development post GDM; and although results from randomized interventional studies more strongly suggested no associations, the conclusion holds a high degree of uncertainty.

Vitamin D-Binding Protein in Pregnancy and Reproductive Health

Vitamin D-binding protein (VDBP), the main carrier of vitamin D, has recently been implicated in reproductive health and pregnancy outcomes including endometriosis, polycystic ovary syndrome (PCOS), pre-eclampsia, and gestational diabetes mellitus (GDM). Improved methods for measuring VDBP and an increased understanding of its role in biological processes have led to a number of newly published studies exploring VDBP in the context of pregnancy. Here, we synthesize the available evidence regarding the role of VDBP in reproductive health and pregnancy, and we highlight areas requiring further study. Overall, low levels of maternal serum VDBP concentrations have been associated with infertility, endometriosis, PCOS and spontaneous miscarriage, as well as adverse pregnancy outcomes including GDM, pre-eclampsia, preterm birth and fetal growth restriction. However, increased VDBP concentration in cervicovaginal fluid has been linked to unexplained recurrent pregnancy loss and premature rupture of membranes. Some genetic variants of VDBP have also been associated with these adverse outcomes. Further studies using more accurate VDBP assays and accounting for ethnic variation and potential confounders are needed to clarify whether VDBP is associated with reproductive health and pregnancy outcomes, and the mechanisms underlying these relationships.

The Effect of Vitamin D Supplementation on Glycaemic Control in Women with Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Vitamin D deficiency is highly prevalent amongst pregnant women and is linked to a range of adverse complications, including gestational diabetes. However, there is no consensus among researchers regarding the impact of vitamin D supplementation in alleviating adverse effects in gestational diabetes. The objective of this systematic review and meta-analysis was to determine whether supplementation of vitamin D given to women with gestational diabetes can promote glycaemic control. EMBASE and PubMed were searched up to November, 2018. The selection criteria included randomised controlled trials of the effect of vitamin D supplementation (1000-4762 IU/day) on pregnant women with gestational diabetes mellitus. Study data and outcome measures (fasting blood glucose, glycated haemoglobin and serum insulin) were extracted from included studies. Random-effects models were used for meta-analyses. Heterogeneity tests, and analysis of the risk of bias were conducted. Most of the studies were graded as having either low risk or moderate risk of bias although two studies had a high risk of bias in the areas of blinding of participants and personnel, and incomplete outcome data. On the other hand, the heterogeneity statistic (I²) ranged from 0-41% in the studies included. Five randomised controlled trials were selected for this review and meta-analysis (involving a total of 173 participants supplemented with vitamin D and 153 participants as control drawn from the studies). Vitamin D supplementation was associated with a decrease in fasting blood glucose by a mean of 0.46 mmol/L (-0.68, -0.25) (p < 0.001), glycated haemoglobin by a mean of 0.37% (-0.65, -0.08) (p < 0.01) and serum insulin concentration by mean of 4.10 µIU/mL (-5.50, -2.71) (p < 0.001) compared to controls. This review shows evidence that vitamin D supplementation has the potential to promote glycaemic control in women with Gestational Diabetes Mellitus (GDM). However, due to the limited number of studies in the meta-analysis, the conclusion should be interpreted with caution. Further studies are needed to fully understand the exact mechanism by which vitamin D influences glucose metabolism.

Changes in Micronutrient Intake and Status, Diet Quality and Glucose Tolerance from Preconception to the Second Trimester of Pregnancy

Data on changes in dietary intake and related blood parameters throughout pregnancy are scarce; moreover, few studies have examined their association with glucose homeostasis. Therefore, we monitored intake of folate, vitamin B6, vitamin B12, vitamin D and iron, their status markers, and diet quality from preconception to the second trimester of pregnancy, and we examined whether these dietary factors were associated with glucose homeostasis during pregnancy. We included 105 women aged 18⁻40 years with a desire to get pregnancy or who were already <24 weeks pregnant. Women at increased gestational diabetes (GDM) risk were oversampled. Measurements were scheduled at preconception (n = 67), and 12 (n =53) and 24 weeks of pregnancy (n =66), including a fasting venipuncture, 75-grams oral glucose tolerance test, and completion of a validated food frequency questionnaire. Changes in micronutrient intake and status, and associations between dietary factors and glucose homeostasis, were examined using adjusted repeated measures mixed models. Micronutrient intake of folate, vitamin B6 and vitamin D and related status markers significantly changed throughout pregnancy, which was predominantly due to changes in the intake of supplements. Micronutrient intake or status levels were not associated with glucose homeostasis, except for iron intake (FE µg/day) with fasting glucose (β = -0.069 mmol/L, p = 0.013) and HbA1c (β = -0.4843 mmol, p = 0.002). Diet quality was inversely associated with fasting glucose (β = -0.006 mmol/L for each DHD15-index point, p = 0.017). It was shown that micronutrient intakes and their status markers significantly changed during pregnancy. Only iron intake and diet quality were inversely associated with glucose homeostasis.

The role of vitamin D in perinatology. An up-to-date review

The role of vitamin D in perinatology is a subject of major interest in current medicine. There is growing evidence about the role of maternal vitamin D levels in pregnancy outcomes. The aim of this review is to summarize the current literature about the role of vitamin D in perinatology. Evidence from this review suggests associations between low levels of maternal vitamin D and higher risk of certain obstetrical complications. Vitamin D has been found to be related to preeclampsia, gestational diabetes mellitus, low birth weight, and preterm birth. The current literature supports vitamin D supplementation in pregnant women, but more high-quality data are necessary. The problem that remains is how to achieve an optimal 25-hydroxyvitamin D level. To determine the real benefits of vitamin D supplementation in pregnancy, we need high-quality trials in larger groups.

Vitamin D: effects on pregnancy, maternal, fetal and postnatal outcomes

A high prevalence of vitamin D deficiency and its negative consequences for health is identified as area of primary concern for scientists and clinicians worldwide. Vitamin D deficiency affects not only bone health but many socially significant acute and chronic diseases. Observational studies support that pregnant and lactating women, children and teenagers represent the high risk groups for developing vitamin D deficiency. Current evidence highlights a crucial role of vitamin D in providing the fetal life-support system and fetus development, including implantation, placental formation, intra - and postpartum periods. Hypovitaminosis D during pregnancy is associated with a higher incidence of placental insufficiency, spontaneous abortions and preterm birth, preeclampsia, gestational diabetes, impaired fetal and childhood growth, increased risk of autoimmune diseases for offsprings. Potential mechanisms for the observed associations contain metabolic, immunomodulatory and antiinflammatory effects of vitamin D. Epigenetic modifications in vitamin D-associated genes and fetal programming are of particular interest. The concept of preventing vitamin D deficiency is actively discussed, including supplementation in different ethnic groups, required doses, time of initiation and therapy duration, influence on gestation and childbirth. An adequate supply of vitamin D during pregnancy improves the maternal and fetal outcomes, short and long term health of the offspring. Still current data on relationship between maternal vitamin D status and pregnancy outcomes remains controversial. The large observational and interventional randomized control trials are required to create evidence-based guidelines for the supplementation of vitamin D in pregnant and lactating women.

Gestational diabetes mellitus: Multi-disciplinary treatment approaches

Gestational diabetes mellitus (GDM) is the most common metabolic disease of pregnancy, associated with several perinatal complications. Adequate glycemic control has been proved to decrease risk of GDM-related complications. Several studies have shown the beneficial effect of exercise and medical nutrition treatment on glycemic and weight control in GDM-affected women. Moreover, pharmacological agents, such as insulin and specific oral anti-diabetic agents can be prescribed safely during pregnancy, decreasing maternal blood glucose and, thus, perinatal adverse outcomes. Multi-disciplinary treatment approaches that include both lifestyle modifications (medical nutritional therapy and daily physical exercise) and pharmacological treatment, in cases of failure of the former, constitute the most effective approach. Insulin is the gold standard pharmacological agent for GDM treatment. Metformin and glyburide are two oral anti-diabetic agents that could serve as alternative, although not equal in terms of effectiveness and safety, treatment for GDM. As studies on short-term safety of metformin are reassuring, in some countries it is considered as first-line treatment for GDM management. More studies are needed to investigate the long-term effects on offspring. As safety issues have been raised on the use of glyburide during pregnancy, it must be used only when benefits surpass possible risks.

Treatments for women with gestational diabetes mellitus: an overview of Cochrane systematic reviews

BACKGROUND

Successful treatments for gestational diabetes mellitus (GDM) have the potential to improve health outcomes for women with GDM and their babies.

OBJECTIVES

To provide a comprehensive synthesis of evidence from Cochrane systematic reviews of the benefits and harms associated with interventions for treating GDM on women and their babies.

METHODS

We searched the Cochrane Database of Systematic Reviews (5 January 2018) for reviews of treatment/management for women with GDM. Reviews of pregnant women with pre-existing diabetes were excluded.Two overview authors independently assessed reviews for inclusion, quality (AMSTAR; ROBIS), quality of evidence (GRADE), and extracted data.

MAIN RESULTS

We included 14 reviews. Of these, 10 provided relevant high-quality and low-risk of bias data (AMSTAR and ROBIS) from 128 randomised controlled trials (RCTs), 27 comparisons, 17,984 women, 16,305 babies, and 1441 children. Evidence ranged from high- to very low-quality (GRADE). Only one effective intervention was found for treating women with GDM.EffectiveLifestyle versus usual careLifestyle intervention versus usual care probably reduces large-for-gestational age (risk ratio (RR) 0.60, 95% confidence interval (CI) 0.50 to 0.71; 6 RCTs, N = 2994; GRADE moderate-quality).PromisingNo evidence for any outcome for any comparison could be classified to this category.Ineffective or possibly harmful Lifestyle versus usual careLifestyle intervention versus usual care probably increases the risk of induction of labour (IOL) suggesting possible harm (average RR 1.20, 95% CI 0.99 to 1.46; 4 RCTs, N = 2699; GRADE moderate-quality).Exercise versus controlExercise intervention versus control for return to pre-pregnancy weight suggested ineffectiveness (body mass index, BMI) MD 0.11 kg/m², 95% CI -1.04 to 1.26; 3 RCTs, N = 254; GRADE moderate-quality).Insulin versus oral therapyInsulin intervention versus oral therapy probably increases the risk of IOL suggesting possible harm (RR 1.3, 95% CI 0.96 to 1.75; 3 RCTs, N = 348; GRADE moderate-quality).Probably ineffective or harmful interventionsInsulin versus oral therapyFor insulin compared to oral therapy there is probably an increased risk of the hypertensive disorders of pregnancy (RR 1.89, 95% CI 1.14 to 3.12; 4 RCTs, N = 1214; GRADE moderate-quality).InconclusiveLifestyle versus usual careThe evidence for childhood adiposity kg/m² (RR 0.91, 95% CI 0.75 to 1.11; 3 RCTs, N = 767; GRADE moderate-quality) and hypoglycaemia was inconclusive (average RR 0.99, 95% CI 0.65 to 1.52; 6 RCTs, N = 3000; GRADE moderate-quality).Exercise versus controlThe evidence for caesarean section (RR 0.86, 95% CI 0.63 to 1.16; 5 RCTs, N = 316; GRADE moderate quality) and perinatal death or serious morbidity composite was inconclusive (RR 0.56, 95% CI 0.12 to 2.61; 2 RCTs, N = 169; GRADE moderate-quality).Insulin versus oral therapyThe evidence for the following outcomes was inconclusive: pre-eclampsia (RR 1.14, 95% CI 0.86 to 1.52; 10 RCTs, N = 2060), caesarean section (RR 1.03, 95% CI 0.93 to 1.14; 17 RCTs, N = 1988), large-for-gestational age (average RR 1.01, 95% CI 0.76 to 1.35; 13 RCTs, N = 2352), and perinatal death or serious morbidity composite (RR 1.03; 95% CI 0.84 to 1.26; 2 RCTs, N = 760). GRADE assessment was moderate-quality for these outcomes.Insulin versus dietThe evidence for perinatal mortality was inconclusive (RR 0.74, 95% CI 0.41 to 1.33; 4 RCTs, N = 1137; GRADE moderate-quality).Insulin versus insulinThe evidence for insulin aspart versus lispro for risk of caesarean section was inconclusive (RR 1.00, 95% CI 0.91 to 1.09; 3 RCTs, N = 410; GRADE moderate quality).No conclusions possibleNo conclusions were possible for: lifestyle versus usual care (perineal trauma, postnatal depression, neonatal adiposity, number of antenatal visits/admissions); diet versus control (pre-eclampsia, caesarean section); myo-inositol versus placebo (hypoglycaemia); metformin versus glibenclamide (hypertensive disorders of pregnancy, pregnancy-induced hypertension, death or serious morbidity composite, insulin versus oral therapy (development of type 2 diabetes); intensive management versus routine care (IOL, large-for-gestational age); post- versus pre-prandial glucose monitoring (large-for-gestational age). The evidence ranged from moderate-, low- and very low-quality.

AUTHORS' CONCLUSIONS

Currently there is insufficient high-quality evidence about the effects on health outcomes of relevance for women with GDM and their babies for many of the comparisons in this overview comparing treatment interventions for women with GDM. Lifestyle changes (including as a minimum healthy eating, physical activity and self-monitoring of blood sugar levels) was the only intervention that showed possible health improvements for women and their babies. Lifestyle interventions may result in fewer babies being large. Conversely, in terms of harms, lifestyle interventions may also increase the number of inductions. Taking insulin was also associated with an increase in hypertensive disorders, when compared to oral therapy. There was very limited information on long-term health and health services costs. Further high-quality research is needed.

Vitamin D: Effects on human reproduction, pregnancy, and fetal well-being

Pregnancy places exceptional demands on vitamin D and calcium availability; thus, their deficiencies during pregnancy threaten the woman and her fetus. Globally, vitamin D and other micronutrient deficiencies are common during pregnancy, especially in developing countries where pregnant women have less access to nutritional supplements. Vitamin D deficiency has been reported to be as high as 40% among pregnant women. As a pregnancy progresses, the requirements for vitamin D increase and thus, can worsen preexisting hypovitaminosis D. Consequently, hypovitaminosis D is increasingly associated with a higher incidence of fetal miscarriage, preeclampsia, gestational diabetes, bacterial vaginosis, and impaired fetal and childhood growth and development. This review explores the recent advances in the understanding of vitamin D and the pivotal role it plays in human reproduction, with an emphasis on pregnancy and its outcomes. Given the seriousness of the issue, there is a pressing need for clinicians to become aware of the risks associated with not identifying and correcting vitamin D deficiency. Identifying and correcting vitamin D deficiency, including safe exposure to sunlight, is particularly relevant for those who seek assistance with fertility issues or prenatal counseling, and those in the beginning of their pregnancy. The data point to a significant protective effects of vitamin D during pregnancy when the 25(OH)D serum level exceeds 30 ng/mL before pregnancy and during the first trimester and, sufficient levels are maintained throughout the pregnancy.

Prepregnancy habitual intake of vitamin D from diet and supplements in relation to risk of gestational diabetes mellitus: A prospective cohort study

BACKGROUND

Vitamin D may play a pivotal role in regulating insulin secretion and insulin sensitivity. However, the effect of vitamin D intake, either from the diet or from supplements, on the development of gestational diabetes mellitus (GDM) remains unclear. We prospectively examined the association of prepregnancy habitual intake of vitamin D from diet and supplements with the risk of incident GDM in a well-established cohort.

METHODS

The present study was performed on 21 356 singleton pregnancies from 15 225 women in the Nurses' Health Study II cohort. Diet information, including vitamin D intake from food sources and supplements, was assessed in 1991 and every 4 years thereafter by validated food frequency questionnaires. Log-binomial models with generalized estimating equations were used to estimate relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS

During 10 years of follow-up, 865 incident GDM cases were documented. After adjustment for age, parity, race/ethnicity, family history of diabetes, dietary and lifestyle factors, and body mass index, the RRs (95% CIs) of GDM risk associated with supplemental vitamin D intake of 0, 1-399, and ≥400 IU/day were 1.00 (reference), 0.80 (0.67-0.96), and 0.71 (0.56-0.90), respectively (P_trend  = 0.002). Dietary and total vitamin D intakes were also inversely associated with GDM risk, but the associations were not statistically significant.

CONCLUSIONS

Prepregnancy supplemental vitamin D intake was significantly and inversely associated with risk of GDM. This study indicates potential benefits of increasing vitamin D intake from supplements in the prevention of GDM in women of reproductive age.

Maternal vitamin D status, gestational diabetes and infant birth size

BACKGROUND

Maternal vitamin D status has been associated with both gestational diabetes mellitus (GDM) and fetal growth restriction, however, the evidence is inconsistent. In Finland, maternal vitamin D status has improved considerably due to national health policies. Our objective was to compare maternal 25-hydroxy vitamin D concentrations [25(OH)D] between mothers with and without GDM, and to investigate if an association existed between maternal vitamin D concentration and infant birth size.

METHODS

This cross-sectional study included 723 mother-child pairs. Mothers were of Caucasian origin, and infants were born at term with normal birth weight. GDM diagnosis and birth size were obtained from medical records. Maternal 25(OH)D was determined on average at 11 weeks of gestation in pregnancy and in umbilical cord blood (UCB) at birth.

RESULTS

GDM was observed in 81 of the 723 women (11%). Of the study population, 97% were vitamin D sufficient [25(OH)D ≥ 50 nmol/L]. There was no difference in pregnancy 25(OH)D concentration between GDM and non-GDM mothers (82 vs 82 nmol/L, P = 0.99). Regression analysis confirmed no association between oral glucose tolerance test results and maternal 25(OH)D (P > 0.53). Regarding the birth size, mothers with optimal pregnancy 25(OH)D (≥ 80 nmol/L) had heavier newborns than those with suboptimal pregnancy 25(OH)D (P = 0.010). However, mothers with optimal UCB 25(OH)D had newborns with smaller head circumference than those with suboptimal 25(OH)D (P = 0.003), which was further confirmed as a linear association (P = 0.024).

CONCLUSIONS

Maternal vitamin D concentration was similar in mothers with and without GDM in a mostly vitamin D sufficient population. Associations between maternal vitamin D status and birth size were inconsistent. A sufficient maternal vitamin D status, specified as 25(OH)D above 50 nmol/L, may be a threshold above which the physiological requirements of pregnancy are achieved.

TRIAL REGISTRATION

The project protocol is registered in ClinicalTrials.gov in November 8, 2012 ( NCT01723852 ).

Effect of Vitamin D Supplementation on the Incidence of Gestational Diabetes

Background:

The aim of this study was survey of the effect of Vitamin D supplementation on the incidence of gestational diabetes (GDM) in pregnant women.

Materials and Methods:

This randomized clinical trial was conducted at Alzahra and Shahid Beheshti Hospital in Isfahan, Iran, from January, 2013 to January, 2014 on 210 pregnant women referred to gynecology clinics. Serum levels of Vitamin D were measured, and those with lower serum levels of 10 nmol/L randomly divided into two groups of A and B. Pregnant women with normal Vitamin D level assigned as Group C. Group A was given 50,000 IU Vitamin D supplement every 2 weeks for 10 weeks, and Group B were given the omega-3 pearl as placebo. Then, the incidence of GDM was measured in 24–26 weeks of pregnancy with glucose tolerance test and compared in three groups. Data were analyzed using SPSS version 20 by descriptive statistics, Chi-square and Logistic regression.

Results:

The mean age of participants was 24.76 years (8.02 standard deviation, range 16–36 years). The incidence of GDM at 24–26 weeks gestational age were 8.57% in normal Vitamin D group, 10.00% in Vitamin D deficiency with treatment group, and 11.43% in Vitamin D deficiency without treatment group. The difference between groups in terms of incidence of GDM was not statistically significant (P = 0.112).

Conclusion:

Vitamin D supplementation had not effect on incidence of GDM during pregnancy.

Rationale and Design of Khuzestan Vitamin D Deficiency Screening Program in Pregnancy: A Stratified Randomized Vitamin D Supplementation Controlled Trial

BACKGROUND

Although there have been marked improvements in our understanding of vitamin D functions in different diseases, gaps on its role during pregnancy remain. Due to the lack of consensus on the most accurate marker of vitamin D deficiency during pregnancy and the optimal level of 25-hydroxyvitamin D, 25(OH)D, for its definition, vitamin D deficiency assessment during pregnancy is a complicated process. Besides, the optimal protocol for treatment of hypovitaminosis D and its effect on maternal and neonatal outcomes are still unclear.

OBJECTIVE

The aim of our study was to estimate the prevalence of vitamin D deficiency in the first trimester of pregnancy and to compare vitamin D screening strategy with no screening. Also, we intended to compare the effectiveness of various treatment regimens on maternal and neonatal outcomes in Masjed-Soleyman and Shushtar cities of Khuzestan province, Iran.

METHODS

This was a two-phase study. First, a population-based cross-sectional study was conducted; recruiting 1600 and 900 first trimester pregnant women from health centers of Masjed-Soleyman and Shushtar, respectively, using stratified multistage cluster sampling with probability proportional to size (PPS) method. Second, to assess the effect of screening strategy on maternal and neonatal outcomes, Masjed-Soleyman participants were assigned to a screening program versus Shushtar participants who became the nonscreening arm. Within the framework of the screening regimen, an 8-arm blind randomized clinical trial was undertaken to compare the effects of various treatment protocols. A total of 800 pregnant women with vitamin D deficiency were selected using simple random sampling from the 1600 individuals of Masjed-Soleyman as interventional groups. Serum concentrations of 25(OH)D were classified as: (1) severe deficient (<10ng/ml), (2) moderate deficient (10-20ng/ml), and (3) normal status (>20ng/ml). Those with severe and moderate deficiency were randomly divided into 4 subgroups and received vitamin D3 based on protocol and were followed until delivery. Data was analyzed according to the intention-to-treat principle.

RESULTS

Recruitment commenced in July, 2014, and as estimated, nearly 3.5 years is needed to complete the study. Results of this study will (1) provide reliable information regarding the prevalence of vitamin D deficiency during pregnancy using universal vitamin D screening approach and (2) determine the beneficial effects of universal screening and compare the various treatment protocols in terms of pregnancy outcomes.

CONCLUSIONS

Since vitamin D deficiency is a prevalent disorder in pregnancy among Iranian population, this study will ensure creation of reliable evidence-based findings and will enable clinicians to better evaluate and treat vitamin D deficient pregnant women.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN): 2014102519660N1; http://www.irct.ir/searchresult.php?keyword=&id=19660&number=1&prt=7805&total=10&m=1 (Archived by WebCite at http://www.webcitation.org/6p3lkqFdV).

Evaluation of Relationship between Body Mass Index with Vitamin D Receptor Gene Expression and Vitamin D Levels of Follicular Fluid in Overweight Patients with Polycystic Ovary Syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder associated with reproductive disorders and metabolic dysfunctions including insulin resistance. The roles of vitamin D in the regulation of metabolic modulations specifically involving insulin and reproduction processing are introduced. In addition, obesity appears to be closely associated with severity of PCOS. The present study is to evaluate the effect of body mass index (BMI) on vitamin D levels in follicular fluid and vitamin D receptor (VDR) expression levels in granulos cells.

MATERIALS AND METHODS

A comparative study was conducted on 80 women with average age of 20-35 years referred for in vitro fertilization (IVF). Patients were divided into four groups, and serum levels of testosterone and insulin resistance (IR) were evaluated at the puncture time. Also, vitamin D levels of follicular fluid were evaluated. VDR gene expression was assayed by quantified-polymerase chain reaction (PCR) technique. Correlations were evaluated with calculation of the Spearman coefficient, and also independent relationships were assessed by means of multiple regression analysis.

RESULTS

Vitamin D levels of follicular fluid decreased in PCOS patients compared with non-PCOS. Also, over-weight individuals had lower vitamin D levels compared with normal-weight patients. Vitamin D levels of follicular fluid were highly correlated with BMI (r=-0.51, P<0.01). Homeostatic model assessment-IR (HOMA-IR) values were significantly higher in women of PCOS/overweight and PCOS/normal weight in comparison with women of non-PCOS/normal weight (P<0.01). The gene expression data of VDR in granulosa cells were significantly lower in the PCOS/overweight group compared with the non-PCOS/normal weight (P<0.01).

CONCLUSION

The findings indicated significant differences in VDR gene expression in granulosa cells and vitamin D of follicular fluid in PCOS/overweight patients.

Vitamin D deficiency and impaired placental function: potential regulation by glucocorticoids?

Maternal vitamin D deficiency has been implicated in a range of pregnancy complications including preeclampsia, preterm birth and intrauterine growth restriction. Some of these adverse outcomes arise from alterations in placental function. Indeed, vitamin D appears critical for implantation, inflammation, immune function and angiogenesis in the placenta. Despite these associations, absence of the placental vitamin D receptor in mice provokes little effect. Thus, interactions between maternal and fetal compartments are likely crucial for instigating adverse placental changes. Indeed, maternal vitamin D deficiency elicits changes in glucocorticoid-related parameters in pregnancy, which increase placental and fetal glucocorticoid exposure. As in utero glucocorticoid excess has a well-established role in eliciting placental dysfunction and fetal growth restriction, this review proposes that glucocorticoids are an important consideration when understanding the impact of vitamin D deficiency on placental function and fetal development.

Effects of vitamin D supplementation on metabolic indices and hs-CRP levels in gestational diabetes mellitus patients: a randomized, double-blinded, placebo-controlled clinical trial

BACKGROUND/OBJECTIVES

Vitamin D plays an important role in the etiology of gestational diabetes mellitus (GDM). This study evaluated the effect of vitamin D supplementation on metabolic indices and hs-C-reactive protein (CRP) levels in GDM patients.

SUBJECTS/METHODS

The study was a randomized, placebo-controlled, double-blinded clinical trial. Seventy-six pregnant women with GDM and gestational age between 24-28 weeks were assigned to receive four oral treatments consisting of 50,000 IU of vitamin D3 (n = 38) or placebo (n = 38) once every 2 weeks for 2 months. Fasting blood glucose (FG), insulin, HbA1c, 25-hydroxyvitamin D, lipid profile, hs-CRP, and homeostasis model assessment-insulin resistance (HOMA-IR) were measured before and after treatment. Independent and paired t-tests were used to determine intra- and intergroup differences, respectively. ANCOVA was used to assess the effects of vitamin D supplementation on biochemical parameters.

RESULTS

Compared with the placebo group, in the vitamin D group, the serum level of 25-hydroxyvitamin D increased (19.15 vs. -0.40 ng/ml; P < 0.01) and that of FG (-4.72 vs. 5.27 mg/dl; P = 0.01) as well as HbA1c (-0.18% vs. 0.17%; P = 0.02) decreased. Improvements in the lipid profiles were observed in the vitamin D group, but without statistical significance. Significant increases in concentrations of hs-CRP, FG, HbA1c, total cholesterol, and LDL cholesterol were observed in the placebo group. No significant change in fasting insulin and HOMA-IR was observed in either group.

CONCLUSIONS

In GDM patients, vitamin D supplementation improved FG and HbA1c but had no significant effects on lipid profile or hs-CRP.

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.

Inverse association between maternal 25OHD level and cord GLP-1/GIP concentrations

BACKGROUND

Because vitamin D may have beneficial effects on glucose metabolism in pregnant women with gestational diabetes mellitus, we explored whether maternal 25-hydroxyvitamin D (25OHD) levels in normal pregnancy have association with diabetes-related hormone levels and glycated albumin (GA).

METHODS

A prospective cohort study was performed to collect serum samples from 612 pairs of pregnant women and cord blood of their offspring. Levels of 25OHD and GA in maternal and cord blood were measured by radioimmunoassay and enzyme assay, respectively. Using cord serum, 12 diabetes-related hormones were assayed. Spearman's rank correlation coefficient was used to quantify the strength of association between biomarkers.

RESULTS

A prominent association between maternal and cord 25OHD levels (r = 0.76, 95% confidence intervals (CIs): 0.73-0.79, P < 0.0001) and weak association between maternal and cord GA (r = 0.22, 95% CIs: 0.14-0.30, P < 0.0001) were shown. Among the 12 diabetes-related hormones, both maternal and cord 25OHD levels showed prominent negative associations with glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

CONCLUSIONS

These results suggest that decreased maternal 25OHD may be associated with decreased cord 25OHD and increased cord GLP-1 and GIP levels, which may be involved with the transfer of maternal glucose to the fetus.

Effect of vitamin D supplementation on insulin resistance and glycaemic control in prediabetes: a systematic review and meta-analysis

AIMS

To evaluate the effect of vitamin D on insulin resistance and glycaemic control in prediabetes.

METHODS

A literature search was conducted of MEDLINE, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, Web of Science and www.clinicaltrials.gov, together with a historical search through the reference lists of relevant articles until end of June 2014. Studies were included if they were randomized controlled trials of vitamin D or vitamin D analogues in prediabetes and if they reported homeostatic model assessment of insulin resistance or 2-h plasma glucose after oral glucose tolerance test. Treatment effect was estimated according to mean difference in the changes from baseline of homeostatic model assessment of insulin resistance, 2-h oral glucose tolerance test plasma glucose, fasting plasma glucose and HbA1c between vitamin D and control groups. Meta-analysis of eligible studies was performed.

RESULTS

A total of 10 randomized controlled trials were included. Vitamin D did not significantly improve homeostatic model assessment of insulin resistance and 2-h oral glucose tolerance test plasma glucose: the mean differences were -0.06 (95% CI -0.36 to 0.24) and -0.23 mmol/l (95% CI -0.65 to 0.19), respectively. Subgroup analysis suggested that vitamin D improved homeostatic model assessment of insulin resistance in a subgroup with baseline 25-hydroxyvitamin D ≥ 50 nmol/l [mean difference -0.59 (95% CI -1.14 to -0.04); P = 0.03] and improved 2-h oral glucose tolerance test plasma glucose in the subgroup with baseline 25-hydroxyvitamin D < 50 nmol/l [mean difference -0.68 mmol/l (95% CI -1.35 to -0.01); P = 0.05]. Vitamin D significantly reduced fasting plasma glucose and HbA1c levels. The mean differences were -0.10 mmol/l (95% CI -0.18 to -0.03), P = 0.006 and -1 mmol/mol (95% CI -2 to 0), P = 0.008, respectively.

CONCLUSIONS

No beneficial effect of vitamin D in improving insulin resistance was identified.

Vitamin D and the Promotion of Long-Term Metabolic Health from a Programming Perspective

Studies linking vitamin D and long-term metabolic health have generated much debate. Recommendations for the intake of vitamin D by the general public and by the health care professionals have been complicated by a number of inconsistencies in the literature. These caveats relate to the methodological approaches, differences in the populations (and the species) of study, and the definitions used for thresholds of vitamin D status. This review addresses current evidence available for assessing the potential programming of long-term metabolic health of offspring by maternal vitamin D status in pregnancy. It summarizes knowledge on the early origins of metabolic health and analyzes evidence for an association between the vitamin D status in pregnancy and maternal and fetal health status. In addition, we analyze the link between the regulation of inflammation and the vitamin D status in the general population to inform on the general mechanisms through which early vitamin D might affect the programming of long-term health. The evidence suggests an association between the vitamin D status in early life and the programming of long-term health. However, to the best of our knowledge, the current finding is insufficient to draw a final conclusion for evidence-based preventive actions. The data warrant replication in prospective studies and additional research substantiating the causal factors and pathways.

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.

Relationship between mean platelet volume and vitamin D deficiency in gestational diabetes mellitus

OBJECTIVE

To investigate whether vitamin D deficiency is associated with high mean platelet volume (MPV) in pregnancies diagnosed with gestational diabetes mellitus (GDM) compared to healthy pregnancies.

SUBJECTS AND METHODS

This study included 200 pregnant women. 25-hydroxyvitamin D3(25(OH)D3) and MPV values were monitored between pregnant women with GDM and normal glucose metabolism. Correlation between 25(OH)D3 and MPV was calculated both in GDM and healthy pregnancies. Both 25(OH)D3 level in different MPV percentile (≤ 50, 50-75, 75-90, ≥ 90 percentile) and MPV value in different 25(OH)D3 level (≤ 10, 10-20, ≥ 20 ng/mL) were calculated.

RESULTS

Low 25(OH)D3 level and high MPV were observed both in GDM group (p = 0.007, p = 0.06, respectively) and in glucose metabolism disorders (GMD) group (p = 0.03, p = 0.04, respectively). There was no significant relationship between 25(OH)D3 and MPV in healthy pregnancies. Whereas, it is observed that there is a negative, but statistically insignificant correlation between MPV and 25(OH)D3 pregnant women with GMD (r = 0.1, r = -0.7, respectively). MPV values had significantly higher in vitamin D deficient group than pregnant women with normal 25(OH)D3 level in GMD group (p = 0.04). The optimal 25(OH)D3 cut off point for predicting future cardiovascular risk was 10.4 ng/ mL (area under curve (AUC) = 0.58).

CONCLUSIONS

Vitamin D deficiency may contribute to an increased risk for future cardiovascular diseases and a risk of thrombotic complications in pregnant women with GDM.

Clinical implications of vitamin D deficiency

Vitamin D deficiency is a common medical problem worldwide and its prevalence rises along with latitude, obesity, sedentary lifestyle, limited sunlight exposure and aging. A great body of evidence has shown that patients with vitamin D deficiency have increased cardiovascular risks and total mortality. Conversely, the presence of comorbidities progressive with age such as abdominal obesity, insulin resistance, type 2 diabetes and hypertension places the patients at an increased risk of vitamin D deficiency. The multidirectional effect of vitamin D deficiency is present in different phases of the aging process. Based on the literature review, the risk factors for vitamin D insufficiency most often found in post-menopausal women include limited sun exposure and time spent outdoors, inadequate dietary vitamin D intake, winter season and increased age. Vitamin D supplementation in this group might offer prevention of falls and fractures and may be beneficial for cardiovascular health, what may be especially important in osteoporotic and elderly populations. Prevention and treatment processes involve education regarding sunlight exposure and pharmacological cholecalciferol supplementation according to the recommendations for Central Europe. This manuscript reviews the role of vitamin D and its deficiency and considers their clinical implications, with particular regard to peri- and postmenopausal women.

Inflammatory and Other Biomarkers: Role in Pathophysiology and Prediction of Gestational Diabetes Mellitus

Understanding pathophysiology and identifying mothers at risk of major pregnancy complications is vital to effective prevention and optimal management. However, in current antenatal care, understanding of pathophysiology of complications is limited. In gestational diabetes mellitus (GDM), risk prediction is mostly based on maternal history and clinical risk factors and may not optimally identify high risk pregnancies. Hence, universal screening is widely recommended. Here, we will explore the literature on GDM and biomarkers including inflammatory markers, adipokines, endothelial function and lipids to advance understanding of pathophysiology and explore risk prediction, with a goal to guide prevention and treatment of GDM.

Vitamin D deficiency in early pregnancy

Objective

Vitamin D deficiency is a common problem in reproductive-aged women in the United States. The effect of vitamin D deficiency in pregnancy is unknown, but has been associated with adverse pregnancy outcomes. The objective of this study was to analyze the relationship between vitamin D deficiency in the first trimester and subsequent clinical outcomes.

Study Design

This is a retrospective cohort study. Plasma was collected in the first trimester from 310 nulliparous women with singleton gestations without significant medical problems. Competitive enzymatic vitamin D assays were performed on banked plasma specimens and pregnancy outcomes were collected after delivery. Logistic regression was performed on patients stratified by plasma vitamin D concentration and the following combined clinical outcomes: preeclampsia, preterm delivery, intrauterine growth restriction, gestational diabetes, and spontaneous abortion.

Results

Vitamin D concentrations were obtained from 235 patients (mean age 24.3 years, range 18-40 years). Seventy percent of our study population was vitamin D insufficient with a serum concentration less than 30 ng/mL (mean serum concentration 27.6 ng/mL, range 13-71.6 ng/mL). Logistic regression was performed adjusting for age, race, body mass index, tobacco use, and time of year. Adverse pregnancy outcomes included preeclampsia, growth restriction, preterm delivery, gestational diabetes, and spontaneous abortion. There was no association between vitamin D deficiency and composite adverse pregnancy outcomes with an adjusted odds ratio of 1.01 (p value 0.738, 95% confidence intervals 0.961-1.057).

Conclusion

Vitamin D deficiency did not associate with adverse pregnancy outcomes in this study population. However, the high percentage of affected individuals highlights the prevalence of vitamin D deficiency in young, reproductive-aged women.

Time for large randomised trials of vitamin D for women with gestational diabetes mellitus to improve perinatal health outcomes

Gestational diabetes mellitus (GDM) affects 7-14% of pregnancies in the USA and its incidence is rising. Several small trials have demonstrated improved insulin sensitivity and glucose tolerance with vitamin D supplementation among women with GDM. In this issue of Diabetologia (DOI: 10.1007/s00125-014-3293-x ), Asemi and colleagues report that co-supplementation of vitamin D and calcium among women with diet-controlled GDM improves several biomarkers of metabolic status, including insulin, glucose and cholesterol. Whether such improvements in biomarkers would translate into clinically meaningful reductions in the harmful sequelae of GDM remains unknown. The promising results from Asemi and colleagues justify investment in large randomised, double-blind, placebo-controlled trials of vitamin D (with or without calcium) for women with GDM. Such trials should be powered for perinatal outcomes such as Caesarean section for macrosomia, postnatal hypoglycaemia and respiratory distress; ideally, the trials would include long-term follow-up of mothers and infants for later metabolic consequences of GDM.

Vitamin D and gestational diabetes: an update

PURPOSE OF REVIEW

Vitamin D status (which is involved in glucose homeostasis) is related to gestational diabetes mellitus (GDM). GDM is characterized by increased resistance to and impaired secretion of insulin and results in higher risk of adverse pregnancy outcomes including operative delivery, macrosomia, shoulder dystocia and neonatal hypoglycemia. Women with GDM and their babies are at increased risk for developing type II diabetes.

RECENT FINDINGS

International definitions of vitamin D deficiency and normality are inconsistent. Vitamin D deficiency is common in pregnant women particularly those with poor diets and who have dark skins living in temperate climes with lack of exposure to sunlight.

SUMMARY

Few interventional studies indicate that supplementation optimizes maternal vitamin D status or improves maternal glucose metabolism. Observational studies about maternal vitamin D status and risk of GDM are conflicting. This could be because of measurement of vitamin D or differences in population characteristics such as ethnicity, geographic location, gestational age at sampling and diagnostic criteria for GDM. Good-quality randomized controlled trials are required to determine whether vitamin D supplementation decreases the risk of GDM or improves glucose tolerance in diabetic women.