Association of maternal serum 25-hydroxyvitamin D concentrations in second and third trimester with risk of gestational diabetes and other pregnancy outcomes

Vitamin D and Gestational Diabetes Mellitus in the IEU OpenGWAS Project: A Two-Sample Bidirectional Mendelian Randomization Study

BACKGROUND

Gestational diabetes mellitus (GDM) is one of the most prevalent pregnancy problems, and there is still debate over the relationship between vitamin D and GDM.

OBJECTIVES

Our objective is to investigate the correlation between vitamin D and GDM by employing Mendelian randomization (MR) with summary data obtained from genome-wide association studies (GWAS).

METHODS

Data on exposures and outcomes, namely vitamin D, vitamin D insufficiency, and GDM, were acquired from the IEU OpenGWAS Project. Bidirectional MR analysis was performed utilizing the inverse variance weighted (IVW) method as the principal analytical approach. The complementary approaches employed in this study encompassed weighted median, simple mode, weighted mode, and MR-Egger regression. A series of sensitivity analysis were conducted in order to assess the reliability of the obtained results.

RESULTS

The data were acquired from the IEU OpenGWAS Project. Following the application of the three assumptions of MR, 13 single nucleotide polymorphisms (SNPs) were included in the MR analysis for vitamin D levels and vitamin D deficiency on GDM, and 10 and 26 SNPs were included for GDM on vitamin D levels and deficiency, respectively. The findings from the IVW analysis revealed a significant positive correlation between vitamin D levels and GDM (OR = 1.057, 95% CI: 1.011-1.104, p = 0.015). Conversely, a negative correlation was seen between vitamin D deficiency and GDM (OR = 0.979, 95% CI: 0.959-0.999, p = 0.039). The results of the reverse MR study revealed no evidence of reverse causation between GDM and vitamin D. The findings from multiple MR approaches were in line with the direction of IVW analysis. Sensitivity analysis revealed no evidence of heterogeneity, pleiotropy, or outliers, suggesting the robustness of the results.

CONCLUSIONS

There exists a causal association between vitamin D and GDM, whereby vitamin D levels serve as a risk factor for GDM.

Maternal vitamin D status and risk of gestational diabetes mellitus in twin pregnancies: a longitudinal twin pregnancies birth cohort study

BACKGROUND

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, with significant short-term and long-term implications for both mothers and their offspring. Previous studies have indicated the potential benefits of vitamin D in reducing the risk of GDM, yet little is known about this association in twin pregnancies. This study aimed to investigate maternal vitamin D status in the second trimester and examine its association with the risk of GDM in twin pregnancies.

METHODS

We conducted a prospective cohort study based on data from the Chongqing Longitudinal Twin Study (LoTiS). Peripheral blood serum was collected from the mothers in the second trimester to measure 25(OH)D concentrations. GDM was diagnosed at 23-26 weeks of gestation using a 75-g 2-h oral glucose tolerance test. We used multivariable logistic regression analyses to examine the correlations between vitamin D status and the risk of GDM.

RESULTS

Of the total participants, 93 (29.9%) women were diagnosed with GDM. The mean serum 25(OH)D concentration in the second trimester was 31.1 ± 11.2 ng/mL, and the rate of vitamin D insufficiency and deficiency were 23.5% and 18.7%, respectively. Compared to women with a 25(OH)D concentration < 30 ng/mL, those with a 25(OH)D concentration ≥ 30 ng/mL had a significantly lower risk of GDM (RR 0.61; 95% CI: 0.43, 0.86), especially those who were overweight before pregnancy (RR 0.32; 95% CI: 0.16, 0.64). The restricted cubic splines model showed an inverted J-shaped relationship between vitamin D concentrations and GDM risk.

CONCLUSIONS

The risk of GDM was significantly reduced in twin pregnant women with vitamin D concentrations ≥ 30 ng/mL in the second trimester.

TRIAL REGISTRATION

ChiCTR-OOC-16,008,203. Retrospectively registered on 1 April 2016.

Early pregnancy exposure of maternal triglyceride levels and its effects on birth weight

OBJECTIVES

The aim of this study was to evaluate the early pregnancy exposure of maternal triglyceride (mTG) and its effects on birth weight, which was an important indicator for nutritional status of newborns, and even its long-term health.

METHODS

A retrospective cohort study was designed to investigate the relationship between mTG in early pregnancy and birth weight. Totally 32,982 women who had a singleton pregnancy and underwent serum lipids screening during early pregnancy were included in this study. Logistic regressions were used to evaluate the correlations between mTG levels and small for gestational age (SGA) or large for gestational age (LGA), and the restricted cubic spline models were applied to explore the dose-response relationship.

RESULTS

The increased mTG levels during early pregnancy decreased the risk of SGA and increased the risk of LGA. The high mTG (>90th, 2.05 mM) was showed associated with higher risk of LGA (AOR, 1.35; 95 %CI, 1.20 to 1.50), and lower risk of SGA (AOR, 0.78; 0.68 to 0.89). Lower risk of LGA (AOR, 0.81; 0.70 to 0.92) was found in those cases of low mTG (<10th, 0.81 mM), but no correlation was found between low mTG levels and the risk of SGA. The results remained robust after excluding women with high or low body mass index (BMI) and pregnancy complications.

CONCLUSIONS

This study suggested that early pregnancy exposure of mTG were related to the occurrence of SGA and LGA. mTG levels higher than 2.05 mM (>90th) were suggested to be avoid because of its risk for LGA, while mTG lower than 0.81 mM (<10th) showed its benefits for ideal birthweight range.

Vitamin D in gestational diabetes: a broadened frontier

Vitamin D deficiency is very common among women of reproductive age, even during pregnancy. Different studies have yielded vastly different results regarding whether vitamin D deficiency during pregnancy affects the development and progression of gestational diabetes mellitus (GDM), glycemic control in patients with hyperglycemia, and maternal-fetal outcomes. In addition, concerns, such as the mechanisms underlying the effect of vitamin D deficiency on glucose metabolism during pregnancy, efficacy of vitamin D supplementation in reducing the risk of developing GDM, and recommended supplemental dose of vitamin D, are yet to be elucidated. This article reviewed the latest domestic and international studies in this field, with a focus on the relationship between vitamin D deficiency and GDM, their underlying pathophysiological mechanisms, and the role of vitamin D intervention in the prevention and treatment of GDM. We recommend vitamin D supplementation as soon as possible for all pregnant women with vitamin D deficiency, especially those with GDM.

Early pregnancy vitamin D insufficiency and gestational diabetes mellitus

OBJECTIVES

To test the hypothesis that a link existed between vitamin D levels in the first trimester and gestational diabetes mellitus (GDM).

METHODS

The 25-hydroxyvitamin D₃ levels were tested in the first trimester and pregnant outcomes were followed up in 1726 women.

RESULTS

Only 5.9% of pregnant women have sufficient 25(OH)D₃ . More women with GDM are in the status of 25(OH)D₃ insufficiency than women with normal glucose tolerance (NGT) (p < 0.05). Age (odds ratio [OR]: 1.047, 95% confidence interval [CI]: 1.014-1.081), pre-pregnancy body mass index (BMI) (OR: 1.132, 95%CI: 1.092-1.173) were risk factors of GDM while 25-(OH) D₃ (OR: 0.979, 95%CI: 0.960-0.999) was a protective factor. After adjusted for maternal age and pre-pregnancy BMI, 25(OH)D₃ insufficiency (<30 ng/mL) is an independent predictor of GDM (OR: 2.122, 95%CI: 1.084-4.155); 25(OH)D₃ level correlated with fasting blood glucose in the first trimester negatively.

CONCLUSION

Vitamin D insufficiency in early pregnancy was significantly associated with an increased risk for GDM in Chinese women.

High Levels of 25-OH-Vitamin D and Copper in Pregnant Women with Abnormal Glucose Challenge Test

Several hormones and elements are involved in the homeostasis of glucose metabolism during pregnancy. This present study determined the differences among the factors involved in glucose regulation for pregnant women with and without an abnormal glucose challenge test (GCT), but without gestational diabetes mellitus, during the second trimester of gestation and the postpartum period. One hundred and six pregnant women who had received routine prenatal and postpartum examinations at our hospital were recruited. Sugar-related tests and the levels of pregnancy-associated hormones and 25-OH-vitamin D were performed using a clinical autoanalyzer; six elements were assessed using graphite furnace atomic absorption spectrometry or inductively coupled plasma mass spectrometry. The women in the abnormal GCT group (n = 27) featured significantly higher levels of 25-OH-vitamin D (p = 0.006) and copper (p < 0.001) than those in the normal GCT group (n = 79). After adjusting for possible pregnancy factors, abnormal GCT remained the significant contributing factor for the elevated levels of 25-OH-vitamin D and copper during gestation (p = 0.046 and 0.002, respectively). Furthermore, significant positive correlations existed between 25-OH-vitamin D and glucose after a 50-g GCT (p = 0.001), 25-OH-vitamin D and HbA_1C (p = 0.004), serum copper and glucose after a 50-g GCT (p = 0.003), and serum copper and HbA_1C (p < 0.001). We conclude that blood 25-OH-vitamin D and copper are strongly correlated with glucose levels during gestation; these two factors are potential clinical predictors for maternal impaired glucose tolerance and, indirectly, for reducing perinatal risks and neonatal complications.

Effect of maternal vitamin D status on risk of adverse birth outcomes: a systematic review and dose-response meta-analysis of observational studies

PURPOSE

Accumulating evidence suggests that vitamin D deficiency increases the risk of adverse perinatal outcomes. However, the dose-response relationship between maternal vitamin D status and adverse birth outcomes remains unclear. Focusing on prospective observational studies, we aimed to explore the dose-response relationship of vitamin D status with the risk of low birth weight (LBW), macrosomia (MA), preterm birth (PTB), small for gestational age (SGA), and intrauterine growth restriction (IUGR).

METHODS

Databases including PubMed, Embase, Scopus, and Web of Science were used up to 19 January 2021 to search for observational studies that fulfilled criteria as follows: cohort studies, case-cohort studies, or nested case-control studies. Random-effects models were used to pool relative risks (RRs) and 95% confidence intervals (CIs) in the observational studies.

RESULTS

A total of 72 publications were included in this systematic review and 71 in the meta-analysis. Maternal 25-hydroxyvitamin D (25(OH)D) concentrations were inversely associated with the risk of LBW (RR: 0.65; 95% CI 0.48-0.86), PTB (RR: 0.67; 95% CI 0.57-0.79), and SGA (RR: 0.61; 95% CI 0.49-0.76) in the highest versus lowest meta-analysis, but not associated with MA and IUGR. Linear dose-response analysis showed that each 25 nmol/L increase in 25(OH)D was associated with a 6% and 10% reduction in the risk of PTB (RR: 0.94; 95% CI 0.90-0.98) and SGA (RR: 0.90; 95% CI 0.84-0.97), respectively.

CONCLUSION

Our study suggests that a sufficient vitamin D status during pregnancy is protective against the risk of LBW, PTB, and SGA.

Interplay between Maternal and Neonatal Vitamin D Deficiency and Vitamin-D-Related Gene Polymorphism with Neonatal Birth Anthropometry

Vitamin D deficiency during pregnancy has been associated with poor foetal growth and neonatal birth anthropometry. However, the associations were inconsistent and could be confounded by neonatal vitamin D status and genetic factors. Until recently, limited studies have concomitantly examined the effect of maternal and neonatal vitamin D deficiency and vitamin D-related single nucleotide polymorphisms (SNPs) on neonatal birth anthropometry. This study aims to examine the independent and combined effects of maternal and neonatal vitamin D deficiency and vitamin-D-related SNPs on neonatal birth anthropometry. This cross-sectional study included 217 mother−neonate dyads recruited from Hospital Serdang, Selangor, Malaysia, between 2015 and 2017. Plasma 25-hydroxyvitamin D (25OHD) concentration was measured in maternal and umbilical cord blood using ultra-high-performance liquid chromatography (UHPLC). Maternal and neonatal vitamin D Receptor (VDR) SNP (rs2228570) genotypes were determined using high-resolution melting (HRM). Group-specific component (GC) SNPs (rs4588 and rs7041) genotypes were determined using restriction fragment length polymorphism. Our results showed that: (1) maternal vitamin D deficiency (25OHD < 30 nmol/L) was inversely associated with birth weight, head circumference and crown−heel length; (2) neonatal SNPs, VDR rs2228570 and GC rs4588, were significantly associated with birth weight and head circumference, respectively; and (3) a potential interaction was observed between maternal VDR rs2228570 with maternal vitamin D deficiency on head circumference. These findings suggest that the underlying mechanisms of vitamin D on foetal growth are likely to be localised in the maternal compartment, mediated through the placenta, rather than through cellular mechanisms within the foetus. Further large-scale studies are warranted to validate and extend these findings.

Association between maternal vitamin D levels and risk of adverse pregnancy outcomes: a systematic review and dose-response meta-analysis

Epidemiological studies have investigated the associations between vitamin D and the risk of adverse pregnancy outcomes; however, the results are conflicting and dose-response relationships remain to be confirmed. This study aimed to summarize previous studies on the associations of vitamin D levels with the risk of gestational diabetes mellitus (GDM), pre-eclampsia (PE), gestational hypertension (GH), and caesarean section (C-section), and to clarify the dose-response trends. PubMed, Embase, Scopus, and Web of Science were searched to identify eligible articles. A total of 69 prospective observational studies including cohort studies, case-cohort studies, or nested case-control studies were included in the current systematic review, of which 68 studies were available for meta-analysis. Compared with the lowest level, the highest level of 25(OH)D was significantly associated with a lower risk of GDM (RR: 0.76; 95% CI: 0.66-0.87), PE (RR: 0.74; 95% CI: 0.60-0.90;), and GH (RR: 0.87; 95% CI: 0.79-0.97); however, no significant relationship was found for C-section (RR: 1.00; 95% CI: 0.90-1.12). There was significant between-study heterogeneity for GDM (I² = 69.2%; P_{heterogeneity} < 0.001), PE (I² = 52.0%; P_{heterogeneity} = 0.001), and C-section (I² = 59.1%; P_{heterogeneity} < 0.001), while no heterogeneity was found for GH (I² = 0.0%; P_{heterogeneity} = 0.676). For each 25 nmol L^-1 increase in 25(OH)D, the pooled RR was 0.92 (95% CI: 0.86-0.97) for GDM and 0.89 (95% CI: 0.84-0.94) for PE, respectively. Notably, the dose-response analysis showed a non-linear relationship between maternal 25(OH)D levels and the risk of PE (P_{non-linearity} = 0.009). Our meta-analysis provides further scientific evidence of the inverse association between 25(OH)D levels and the risk of GDM, PE, and GH, which may be useful for the prevention of pregnancy complications. However, more evidence from prospective studies is needed regarding the dietary intake of vitamin D during pregnancy.

Supplementation of Vitamin D in the Postdelivery Period of Women with Previous Gestational Diabetes Mellitus: Systematic Review and Meta-Analysis of Randomized Trials

OBJECTIVE

 To evaluate the effects of vitamin D supplementation in the postpartum period of women with previous gestational diabetes mellitus (GDM).

METHODS

 Randomized clinical trials of pregnant women with GDM of any chronological, gestational age and parity, with no history of previous disease who received vitamin D supplementation in the prenatal and/or postpartum period and were evaluated in the postpartum period were included. The PubMed, EMBASE, Cochrane, and LILACS databases were consulted until July 2019. Serum vitamin D concentration (25-hydroxyvitamin D in nmol/L), fasting blood glucose, glycated hemoglobin, serum calcium concentration, homeostatic model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), parathyroid hormone (PTH) and body mass index (BMI) were evaluated. Similar results in at least two trials were plotted using the RevMan 5; Cochrane Collaboration, Oxford, Reino Unido. The quality of the evidence was generated according to the classification, development, and evaluation of the classification of the recommendations.

RESULTS

 Four studies were included in the present review (200 women). The findings indicate that there is no difference in the postpartum period in women diagnosed with previous GDM who received vitamin D supplementation in the prenatal and/or in the postpartum period, showing only that there was a significant increase in the concentration of vitamin D (relative risk [RR]: 1.85; 95% confidence interval [CI]: 1.02-2.68).

CONCLUSION

 This increase in the concentration of vitamin D should be interpreted with caution, since the assessment of the quality of the evidence was very low. For the other analyzed outcomes, there was no significance between the intervention and control groups, and the outcomes, when analyzed in their strength of evidence, were considered very low and low in their evaluation.

Second-trimester 25-hydroxyvitamin D status in pregnant women from southern China and risk of macrosomia: a large-scale retrospective cohort study

PURPOSE

The association between maternal vitamin D concentrations and birth weight is controversial. We conducted a large-scale retrospective cohort study in southern China to explore this relationship.

METHODS

From July 2017 to April 2019, we enrolled 10,586 pregnant women and measured serum vitamin D [via 25-hydroxyvitamin D, 25(OH)D] in the second trimester using electrochemiluminescence immunoassays. The association between macrosomia and 25(OH)D was analyzed using logistic regression and ROC curve.

RESULTS

Average vitamin D concentration was 61.1 ± 20.2 nmol/L. Additionally, 31.1% participants had 25(OH)D concentrations <50.0 nmol/L, while 68.9% exhibited concentrations ≥50.0 nmol/L. Of the subjects, 3.2% of women delivered macrosomic infants (neonatal birth weight ≥4000 g) and 96.8% did not. The macrosomia group had lower vitamin D concentrations than the non-macrosomia group (59.5 ± 22.3 vs. 61.2 ± 20.1, p < .05). Approximately a third of each group had vitamin D < 50.0 nmol/L (non-macrosomia, 31.3%; macrosomia, 35.9%; p = .055). After adjusting for confounding variables, women with 25(OH)D ≥ 50.0 nmol/L had 24.3% lower macrosomia risk than women with 25(OH)D < 50.0 nmol/L (adjusted OR = 0.757, 95% CI = 0.599-0.956, p = .0193). The predictive accuracy of vitamin D concentrations for evaluating macrosomia risk was 0.667 area under the ROC curve.

CONCLUSION

Maternal vitamin D levels are negatively correlated with macrosomia. Elevating vitamin D above 50.0 nmol/L may reduce macrosomia incidence.

Maternal vitamin D status and risk of gestational diabetes mellitus: A systematic review and meta-analysis of prospective cohort studies

BACKGROUND

No earlier systematic review and meta-analysis have been done on the association between maternal serum vitamin D status and risk of GDM among prospective studies. The current study was done to systematically review prospective cohort studies (with several years of follow-up) on the association between maternal serum vitamin D deficiency or insufficiency and risk of GDM.

METHODS

Relevant papers published up to January 2020 were searched through PubMed, MEDLINE, SCOPUS, EMBASE, and Google Scholar using suitable keywords. All prospective cohort studies reporting Hazard Ratios (HRs) or Relative Risks (RRs) and 95% Confidence Intervals (CI) for GDM across categories of maternal serum vitamin D status were included.

RESULTS

A total of 29 prospective and nested case-control studies were included in the current systematic review, of which 27 studies had sufficient data for the meta-analysis. Individuals with vitamin D deficiency had a 26% greater risk of developing GDM than those with normal serum vitamin D concentrations (OR: 1.26; 95% CI: 1.13, 1.41). In addition, a significant positive association was seen between combined vitamin D insufficiency and deficiency and risk of developing GDM (OR: 1.23; 95% CI: 1.11, 1.35). Dose-response analysis showed a significant U-shaped non-linear association between serum vitamin D concentrations and risk of developing GDM (P < 0.001), such that those with serum vitamin D concentrations between 40 and 90 nmol/L had significantly reduced risk of GDM.

CONCLUSIONS

We found a significant association between vitamin D deficiency and an increased risk of GDM. The lowest risk of GDM was found among those with a serum vitamin D levels of 40-90 nmol/L. Further studies, including randomized clinical trials, are needed to confirm our findings.

REGISTRATION

PROSPERO (ID: 180722), https://www.crd.york.ac.uk/prospero/.

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.

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.

Vitamin D Status and Pregnancy Complications: Serum 1,25-di-hydroxyl-Vitamin D and its Ratio to 25-hydroxy-Vitamin D are Superior Biomarkers than 25-hydroxy-Vitamin D

Vitamin D (VitD) deficiency during pregnancy has been associated with adverse neonatal outcomes and increased risk of late pregnancy complications. We planned to correlate serum VitD biomarkers; 25-hydroxyvitamin D (25-OH-VitD) and 1,25-dihydroxyvitamin D (1,25-diOH-VitD) levels; and their ratio with the frequency of feto-maternal pregnancy complications. A prospective cross-sectional case-control study was conducted at Aljouf Maternity and Children Hospital, Sakaka, Saudi Arabia, during the period of September 1, 2017 to September 30, 2019. 322 pregnant women were stratified into 2 groups: controls (110 cases) and complicated group (212 cases). The later comprised severe preeclamptic toxemia associated with intrauterine growth restriction (58 cases), gestational diabetes mellitus (GDM; 82 cases), abortion (26 cases), undisturbed ectopic pregnancy (16 cases), premature rupture of membranes (PROM; 14 cases), and, inevitable preterm labour (16 cases). After clinical assessment, peripheral blood samples were collected. Serum biomarkers were measured using specific immunoassays. The direct 1,25-diOH-VitD/25-OH-VitD ratio was calculated. Serum 25-OH-VitD indicated widely spreading VitD deficiency among participants with significantly higher levels in controls vs. GDM subgroup only. 1,25-diOH-VitD levels and the ratio were markedly reduced in the six complicated subgroups vs. controls, with non-significant differences amongst the complicated subgroups. ROC analysis showed very high sensitivity and specificity, to differentiate patients from controls, only for 1,25-diOH-VitD (AUC = 0.965; 0.947 - 0.983, p <0.001) followed by the ratio but not 25-OH-VitD. In conclusions, 25-OH-VitD did not show significant changes except for GDM. 1,25-diOH-VitD levels and the ratio showed strong associations with pregnancy complications. Serum 1,25-di-OH-VitD and its ratio to 25-OH-VitD are more reliable and physiologically relevant biomarkers for VitD status in pregnancy.

Significance of Vitamin D on the Susceptibility of Gestational Diabetes Mellitus - A Meta-Analysis

Vitamin D plays an important role in glucose tolerance by stimulating insulin secretion and evidences suggest a contradictory result on the association between vitamin D status and risk of developing gestational diabetes mellitus (GDM). The present updated meta-analysis has been undertaken to find out the joined effect of vitamin D status on the risk of effect GDM considering previously published articles. Data were collected through literature search using electronic databases to retrieve relevant published research articles using various combinations of the following keywords, "vitamin D," "vitamin D deficiency," "cholecalciferol," "25-hydroxyvitamin D," "25(OH) D," "gestational diabetes mellitus," and "GDM." A total of 36 studies including 7,596 GDM cases and 23,377 non-GDM controls were involved in this study. Overall, pooled meta-analysis showed that pregnant women diagnosed with GDM have 18% higher risk of GDM risk when compared with controls [odds ratio (OR) = 1.18, 95% confidence interval (CI) 1.10-1.25; P = 0.00] with high heterogeneity (I² = 73.29). The mean difference was also significantly different between cases and controls (OR = -0.18, 95% CI - 0.22 to - 0.14; P = 0.00). Subgroup analysis showed significant results with age more than 30 years, Asian and European regions, and case-control, cross-sectional, and nested case-control study design. Low concentration of vitamin D is associated with the development of GDM. Although in future more studies especially systematically designed clinical trials based on vitamin D supplementation with large sample size on different population are needed to elucidate the exact concentration of vitamin D during pregnancy as well as before and after pregnancy.

Association of maternal serum 25-hydroxyvitamin D concentrations with risk of preeclampsia: a nested case-control study and meta-analysis

OBJECTIVES

Whether the maternal vitamin D deficiency is associated with preeclampsia is still an argument. We aimed to assess the association between maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations and risk of preeclampsia in a Chinese population and systematically evaluate published evidence on this association.

METHODS

We conducted a nested case-control study involving 122 pregnant women with preeclampsia and 488 pregnant women whose blood pressure was within the normal range (as controls). For further meta-analysis, 20 studies and our study were included for the final pooled analysis, involving 39,031 participants and 3305 preeclampsia cases with various ethnicities.

RESULTS

The results showed that 65.6% of women with preeclampsia had serum 25(OH)D concentrations <50.0 nmol L^-1 compared with 55.3% of women in controls. The 25(OH)D concentrations were significantly lower in women with preeclampsia than controls [Median (IQR), women with preeclampsia versus controls: 43.3 (35.5, 55.2) versus 47.5 (37.6, 60.4) nmol L^-1, p = .014]. For women with 25(OH)D concentrations <50.0 nmol L^-1, they had a 65% increase in preeclampsia risk (95% CI = 1.02-2.69), as compared with women with 25(OH)D concentrations from 50.0 to 74.9 nmol L^-1. Further, meta-analysis showed that low 25(OH)D concentrations were associated with a significantly increased risk of preeclampsia by 62% (pooled OR = 1.62, 95%CI = 1.36-1.94), and the risk effect of low 25(OH)D concentrations existed in most subgroups.

CONCLUSIONS

Low 25(OH)D concentration in pregnancy was significantly associated with preeclampsia risk, and it may serve as biomarkers for the surveillance of high-risk pregnant women.

Maternal vitamin D deficiency during pregnancy and low birth weight: a systematic review and meta-analysis

OBJECTIVE

The object of the present study was to estimate the relationship between maternal vitamin D deficiency during pregnancy and low birth weight by systematically review prevalence studies.

METHODS

We collected data from relevant studies published up to April 2019 using predefined inclusion/exclusion criteria. And all the studies were searched in PubMed, Embase, Cochrane Library, and Web of Science.

RESULTS

A total of 16 studies met the criteria and were included in the meta-analysis. When compared with normal serum levels of vitamin D, the maternal vitamin D deficiency had an increased risk of low birth weight (OR = 2.39; 95%CI 1.25-4.57; p = .008), and same results were found in the comparison of the mean (the total mean birth weight decreased by 0.08 kg; 95%CI -0.10 to -0.06; p < .001).

CONCLUSION

The evidence from this meta-analysis indicates a consistent association between vitamin D deficiency during pregnancy and an increased risk of low birth weight, and preventing maternal vitamin D deficiency may be an important public health strategy to help decrease the risk of low birth weight.

Relationship between vitamin D status and the vaginal microbiome during pregnancy

OBJECTIVE

Evidence supports an inverse association between vitamin D and bacterial vaginosis (BV) during pregnancy. Furthermore, both the vaginal microbiome and vitamin D status correlate with pregnancy outcome. Women of African ancestry are more likely to experience BV, to be vitamin D deficient, and to have certain pregnancy complications. We investigated the association between vitamin D status and the vaginal microbiome.

STUDY DESIGN

Subjects were assigned to a treatment (4400 IU) or a control group (400 IU vitamin D daily), sampled three times during pregnancy, and vaginal 16S rRNA gene taxonomic profiles and plasma 25-hydroxyvitamin D [25(OH)D] concentrations were examined.

RESULT

Gestational age and ethnicity were significantly associated with the microbiome. Megasphaera correlated negatively (p = 0.0187) with 25(OH)D among women of African ancestry. Among controls, women of European ancestry exhibited a positive correlation between plasma 25(OH)D and L. crispatus abundance.

CONCLUSION

Certain vaginal bacteria are associated with plasma 25(OH)D concentration.

Efficacy of vitamin D supplementation in gestational diabetes mellitus: Systematic review and meta-analysis of randomized trials

BACKGROUND

Trials have examined on the benefits of vitamin D supplementation in pregnant women.

OBJECTIVE

This review aimed to evaluate whether oral vitamin D supplements, when given to pregnant women with gestational diabetes mellitus (GDM), would improve maternal and neonatal outcomes, compared with no treatment or placebo.

METHOD

We performed a systematic review following Cochrane methodology, and randomized trials were included where pregnant women with GDM received vitamin D supplementation versus placebo/no treatment or vitamin D and calcium versus placebo/no treatment. Primary outcomes were preeclampsia, preterm birth, cesarean delivery, gestational hypertension, and adverse events related to vitamin D supplementation. The search strategies were applied to the following databases: MEDLINE, Embase, LILACS, and CENTRAL. Similar outcomes in at least two trials were plotted using Review Manager 5.3 software. The quality of evidence was generated according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

RESULTS

The total of 1224 references were identified, eleven trials were potentially eligible, and six were included in this review (totaling 456 women). The meta-analysis of frequency of cesarean deliveries did not show significant differences between groups, none of the trials evaluated the remaining primary outcomes. For secondary outcomes, our results suggest that vitamin D supplementation in pregnant women with GDM may reduce newborn complications such as hyperbilirubinemia, polyhydramnios (RR: 0.40, 95% CI: 0.23 to 0.68; RR: 0.17, 95% CI: 0.03 to 0.89; respectively), and the need for maternal or infant hospitalization (RR: 0.13; 95% CI: 0.02 to 0.98; RR: 0.40, 95% CI: 0.23 to 0.69). However, the evidence was of low or very low quality.

CONCLUSION

We did not find moderate or high quality evidence indicating that vitamin D supplementation, when compared with placebo, improves glucose metabolism, adverse maternal and neonatal outcomes related to GDM in pregnant women.

Disparities in the timing and measurement methods to assess vitamin D status during pregnancy: A Narrative Review

Studies that examined associations between low circulating 25-hydroxyvitamin D (25(OH)D) and adverse pregnancy outcomes used various designs, assay methods and time points for measurement of 25(OH)D concentrations, which creates some confusion in the current literature. We aimed to investigate the variability in the timing and measurement methods used to evaluate vitamin D status during pregnancy. Analysis of 198 studies published between 1976 and 2017 showed an important variability in the choice of 1) threshold values for 25(OH)D insufficiency or deficiency, 2) 25(OH)D measurement methods, and 3) trimester in which 25(OH)D concentrations were measured. Blood samples were taken once during pregnancy in a large majority of studies, which may not be representative of vitamin D status throughout pregnancy. Most studies reported adjustment for confounding factors including season of blood sampling, but very few studies used the 25(OH)D gold standard assay, the LC-MS/MS. Prospective studies assessing maternal 25(OH)D concentrations 1) by standardized and validated methods, 2) at various time points during pregnancy, and 3) after considering potential confounding factors, are needed.

Association of maternal serum 25-hydroxyvitamin D concentrations in second and third trimester with risk of macrosomia

Whether the maternal vitamin D deficiency is associated with infant birth weight is still an argument. Here, we performed a nested case-control study (545 women who subsequently delivered infant with macrosomia and 1090 controls) to evaluate the association of the maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations with risk of macrosomia. We measured the serum 25(OH)D concentrations by enzyme immunoassays. Logistic regression analysis, receiver-operator characteristic curve analysis and graphical nomogram were used for the statistical analyses. Among women who delivered infant with macrosomia, 71.2% of the women had serum 25(OH)D concentrations <50.0 nmol/L compared with 61.1% of the control women (P < 0.001). For women with concentrations <50.0 nmol/L, they had a 33% increased risk of macrosomia compared with women whose 25(OH)D ranged from 50.0 to 74.9 nmol/L. The risk of macrosomia was significantly increased with the decreasing concentrations of serum 25(OH)D in a dose-dependent manner (P for trend = 0.001). We also observed a threshold for 25(OH)D of 50.0 nmol/L for delivering infant with macrosomia and a predictive accuracy of the 25(OH)D concentrations included panel, with an area under the ROC curve of 0.712 for delivering infant with macrosomia. In conclusion, maternal serum 25(OH)D <50.0 nmol/L is associated with delivering a macrosomic infant, and vitamin D deficiency should be monitored in pregnant women.

Prediction of vaginal birth after cesarean delivery in Chinese parturients

There is an urgent need in China to better predict vaginal birth after cesarean (VBAC) to face the challenge of the second child policy. We aimed to validate a widely used VBAC prediction model (Grobman's model) and a modified version of this model in a Chinese population. In this retrospective cohort study, 444 women with one cesarean delivery and at least one subsequent attempt for a trial of labor in Nanjing, China were included. The considered potential VBAC predictors included Grobman's background variables and five new variables. Overall, a total of 370 women had VBAC, with a success rate of 83.3%. The new background variables "maternal height" and "estimated fetal weight" were considered as two additional predictors for VBAC. The AUC of Grobman's model was 0.831 (95%CI = 0.775-0.886) while the AUC of our modified model with two new variables added was 0.857 (sensitivity = 72.2%, specificity = 83.8%). However, the difference between the AUC of the two models was not significant (Z = -1.69, P = 0.091). We confirmed that Grobman's model was accepted in the Chinese population. A modified model that is supplemented with maternal height and estimated fetal weight needs to be further studied in the Chinese population.

The effect of maternal vitamin D deficiency during pregnancy on body fat and adipogenesis in rat offspring

To evaluate the effects of maternal vitamin D deficiency on body fat and adipogenesis in offspring rats, and explore the potential mechanism, we constructed a vitamin D deficient rat model and performed metabolic activity evaluation, body fat monitoring, biochemical analysis, adipogenesis assay, methylation microarray and RNA-seq for their offspring rats. We found the weight of vitamin D deficient (VDD) offspring was gradually higher than that of control (CLT) offspring, and the difference was significant since 10 weeks old. When compared with CTL offspring, the 24 h heat production, peak blood glucose, adipose tissue volume and blood lipid indexes were significantly increased in VDD offspring at 14 weeks old. Moreover, a significant increase in proliferation rate and number of lipid droplets for pre-adipocytes was also observed in VDD offspring group. DNA methylation profiling showed that compared to CTL group, 608 promoters and 204 CpG islands were differentially methylated in the VDD group, involving 305 genes. When combined with the results of RNA-seq, 141 genes of the methylated genes were differentially expressed. In conclusion, vitamin D deficiency during pregnancy may promote the proliferation and differentiation of pre-adipocytes, which may be associated with methylation alterations of genes, ultimately leading to offspring obesity.

Association of Maternal Serum 25-hydroxyvitamin D Concentrations in Second Trimester with Delivery Mode in A Chinese Population

Objective: To determine the maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations in a Chinese population and investigate its associations with subsequent delivery mode by studying 1924 unrelated pregnant women. Methods: The serum 25(OH)D concentrations was measured by euzymelinked immunosorbent assay (ELISA). Simultaneously, maternal information and subsequent delivery mode were collected. Logistic regression analysis was performed to assess the associations between 25(OH)D concentrations and caesarean section. Results: The median (IQR) serum concentration of 25(OH)D for the total subjects was 43.4 (35.2-56.9) nmol/L. Among them, 1225 (63.7%) women were in the status of 25(OH)D deficiency (< 50.0 nmol/L). The 25(OH)D concentrations showed significant variation by body mass index (BMI), parity and season of sampling. Women with caesarean section was older, and with higher BMI and rate of abnormal pregnancy history, suggesting advanced age, obesity and abnormal pregnancy history may be the risk factors for the subsequent caesarean section. Compared with 25(OH)D from 50.0 to 74.9 nmol/L, women with low 25(OH)D concentrations (< 50.0 nmol/L) was not significantly associated with caesarean section. Only in the subgroup of the women without abnormal pregnancy history, higher 25(OH)D (> 75.0 nmol/L) concentrations could significantly decrease the risk of caesarean section. Conclusion: Vitamin D deficiency is a quite serious problem in Chinese pregnant women. There is no evidence that the maternal serum 25(OH)D concentrations is associated with increased risk of caesarean section.