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

Vitamin D deficiency in pregnant women of ethnic minority: a potential contributor to preeclampsia

OBJECTIVE

We investigated risk for comorbidities and preeclampsia at low vitamin D levels in ethnic minorities.

STUDY DESIGN

Umbilical cord vitamin D (25(OH)D) concentration was determined in urban minorities: 80.9% African American and 17% Hispanic mothers-baby pairs. To identify the correlation between vitamin D levels and high-risk comorbidities which result in preeclampsia, multivariate logistic regression analyses were performed.

RESULT

Below the Institute of Medicine threshold of 25(OH)D for pregnant women (25 ng ml⁻¹), obesity (P=0.055) and pregestational diabetes (odds ratio (OR)=2.056) were observed. The study median was 16 ng ml⁻¹ (<25th percentile), at which gestational hypertension (P=0.042), chronic hypertension (OR=4.842) and pregestational diabetes (OR=3.45) became relevant. The risk for preeclampsia increased 12-fold with gestational hypertension (P=0.003) and 14-fold with combined chronic and gestational hypertension (P=0.001).

CONCLUSION

Pregnant women of ethnic minority had lower median vitamin D levels which may contribute to a potential risk for preeclampsia.

Serum vitamin D insufficiency is related to blood pressure in diabetic pregnancy

BACKGROUND

Vitamin D deficiency in pregnancy has been associated with an increased risk of preeclampsia. However, the association between serum vitamin D and blood pressure in pregnant women has been scarcely evaluated, particularly in women with a high risk of developing hypertensive disorders of pregnancy. We sought to evaluate the association between serum 25-hydroxyvitamin D and blood pressure in pregnant women with gestational diabetes mellitus (GDM).

METHODS

A cohort of 184 pregnant women with GDM was followed during the third trimester of pregnancy and early puerperium. Blood pressure was recorded in all prenatal visits, and serum vitamin D was measured by chemiluminescence immunoassay. Pearson's coefficients and multiple linear regressions were used to study predictors of blood pressure levels.

RESULTS

Women with vitamin D insufficiency (<30ng/mL; n = 159) had higher systolic and diastolic blood pressure than the remaining participants. In white women (n = 136), serum vitamin D levels presented a significant negative correlation with systolic blood pressure at the beginning (r = -0.268; P = 0.002) and at the end of the third trimester (r = -0.203; P = 0.02), and vitamin D significantly affected systolic blood pressure after adjusting for confounders. This was not observed in women of other ethnicities.

CONCLUSIONS

In this cohort of pregnant women with GDM, vitamin D insufficiency was associated with higher blood pressure, and in white women, serum vitamin D was an independent predictor of systolic blood pressure during pregnancy.

Is midtrimester vitamin D status associated with spontaneous preterm birth and preeclampsia?

OBJECTIVE

The objective of this study is to evaluate whether midtrimester maternal vitamin D is associated with preeclampsia < 37 weeks or spontaneous preterm birth (SPTB) < 35 weeks.

STUDY DESIGN

Nested case-control comprising two case subsets: (1) 100 women with preeclampsia < 37 weeks and (2) 100 women with SPB < 35 weeks. Controls consisted of 200 women delivered between 39 and 40 weeks. Stored maternal serum obtained between 15 and 21 weeks was tested for total 25-hydroxy vitamin D (25-OH D) levels using liquid chromatography-tandem mass spectrometry. Mean 25-OH D levels and prevalence of vitamin D insufficiency (25-OH D < 30 ng/mL) and deficiency (25-OH D < 15 ng/mL) were compared.

RESULTS

In this study, 89 preeclampsia, 90 SPTB cases, and 177 controls had valid measurements. Mean midtrimester vitamin D was not significantly different between women with preeclampsia (27.4 ng/mL ± 14.4) and controls (28.6 ± 12.6) (p = 0.46), or SPTB (28.8 ± 13.2) and controls (p = 0.92). After adjusting for potential cofounders, neither vitamin D insufficiency (adjusted odds ratio [OR], 1.1; 95% confidence interval [CI], 0.6-2.0) nor deficiency (adjusted OR, 1.4; 95% CI, 0.7-3.0) was significantly associated with preeclampsia. Likewise, SPTB was not significantly associated with either vitamin D insufficiency or deficiency (adjusted OR, 0.8; 95% CI, 0.4-1.4, adjusted OR, 1.3 or 95% CI, 0.6-3.0, respectively).

CONCLUSION

Midtrimester maternal vitamin D was not significantly associated with preeclampsia < 37 weeks or SPTB < 35 weeks.

The vitamin D hypothesis revisited: race-based disparities in birth outcomes in the United States and ultraviolet light availability

Skin color has been proposed to contribute to race-based health disparities in the United States because of differences in ultraviolet (UV) light-induced vitamin D synthesis. The prediction of this hypothesis, herein named the UVD hypothesis, is that racial disparities in health outcomes are correlated with UV light availability. This paper investigates whether UV light availability is associated with disparities in the rates of low birth weight (LBW) and preterm birth (PTB) between whites and blacks, because these outcomes are thought to be influenced by vitamin D status and to shape disease risk in later life. Data on LBW and PTB from 2007 (n = 2,825,620 births) were compared with data on UV light exposure across the United States. Contrary to the predictions of the UVD hypothesis, LBW and PTB rate disparities were greatest in states with the highest UV light exposure. Notably, income inequality was positively and significantly related to LBW and PTB disparities, even after controlling for UV light availability. The results of this analysis demonstrate that there is a significant environmental gradient in racial disparities in birth outcomes in the United States, but other social or environmental factors associated with living in the southern United States are likely stronger contributors to disparities in birth outcomes than UV light-induced vitamin D status.

Maternal vitamin D status and spontaneous preterm birth by placental histology in the US Collaborative Perinatal Project

The objective of this study was to determine the association between maternal 25-hydroxyvitamin D (25(OH)D) and the risk of spontaneous preterm birth (sPTB) before 35 weeks' gestation. A random subcohort from the US Collaborative Perinatal Project (1959-1965) was sampled (n = 2,629) and augmented with all remaining cases of sPTB before 35 weeks' gestation for a total of 767 cases. Banked serum samples collected at 26 weeks' gestation or earlier were assayed for 25(OH)D. Constructs for vascular histology and inflammatory histology were developed from placental pathology examinations. There was no relationship between 25(OH)D and sPTB among white women. Among nonwhite mothers, serum 25(OH)D levels of 30-<50, 50-<75, and ≥75 nmol/L were associated with reductions of 1.0-1.6 cases of sPTB per 100 live births and 20%-30% reductions in risk of sPTB compared with 25(OH)D levels less than 30 nmol/L after adjustment for prepregnancy body mass index (weight (kg)/height (m)(2)), season, and other confounders. This association was driven by inflammation-mediated cases of sPTB and sPTB cases without placental lesions. A sensitivity analysis for unmeasured confounding by exercise, fish intake, and skin color suggested some bias away from the null in the conventional results, but conclusions were generally supported. The vitamin D-sPTB relationship should be examined in modern cohorts with detailed data on skin pigmentation and other covariates.

Vitamin D and maternal and child health: overview and implications for dietary requirements

The essentiality of vitamin D for normal growth and development has been recognized for over 80 years, and vitamin D fortification programs have been in place in the United States for more than 70 years. Despite the above, vitamin D deficiency continues to be a common finding in certain population groups. Vitamin D deficiency has been suggested as a potential risk factor for the development of preeclampsia, and vitamin D deficiency during infancy and early childhood is associated with an increased risk for numerous skeletal disorders, as well as immunological and vascular abnormalities. Vitamin D deficiency can occur through multiple mechanisms including the consumption of diets low in this vitamin and inadequate exposure to environmental ultraviolet B rays. The potential value of vitamin D supplementation in high-risk pregnancies and during infancy and early childhood is discussed. Currently, there is vigorous debate concerning what constitutes appropriate vitamin D intakes during early development as exemplified by differing recommendations from the Institute of Medicine Dietary Reference Intake report and recent recommendations by the Endocrine Society. As is discussed, a major issue that needs to be resolved is what key biological endpoint should be used when making vitamin D recommendations for the pregnant woman and her offspring.

Vitamin D status among preterm and full-term infants at birth

BACKGROUND

Risk factors for maternal vitamin D deficiency and preterm birth overlap, but the distribution of 25-hydroxyvitamin D (25(OH)D) levels among preterm infants is not known. We aimed to determine the associations between 25(OH)D levels and gestational age.

METHODS

We measured umbilical cord plasma levels of 25(OH)D from 471 infants born at Brigham and Women's Hospital in Boston. We used generalized estimating equations to determine whether preterm (<37 wks' gestation) or very preterm (<32 wks' gestation) infants had greater odds of having 25(OH)D levels below 20 ng/ml than more mature infants. We adjusted for potential confounding by season of birth, maternal age, race, marital status, and singleton or multiple gestation.

RESULTS

Mean cord plasma 25(OH)D level was 34.0 ng/ml (range: 4.1-95.3 and SD: 14.1). Infants born before 32 wks' gestation had increased odds of having 25(OH)D levels below 20 ng/ml in unadjusted (odds ratio (OR): 2.2; 95% confidence interval (CI): 1.1-4.3) and adjusted models (OR: 2.4; 95% CI: 1.2-5.3) as compared with more mature infants.

CONCLUSION

Infants born in <32 wks' gestation are at higher risk than more mature infants for low 25(OH)D levels. Further investigation of the relationships between low 25(OH)D levels and preterm birth and its sequelae is thus warranted.

Vitamin D and gestational diabetes mellitus

Gestational diabetes mellitus (GDM) complicates 7 %-14 % of pregnancies in the United States. Vitamin D deficiency also is common in pregnancy. Emerging evidence suggests that Vitamin D administration can improve insulin sensitivity and glucose tolerance, but whether vitamin D supplementation can prevent GDM is unknown. Observational studies provide conflicting evidence as to whether low serum 25-hydroxyvitmain D (25(OH)D) levels are associated with GDM. Two recent systematic reviews concluded that vitamin D deficiency is associated with a higher risk of GDM. However, these reviews are limited by the observational and diverse nature of the included studies. Of greatest concern is the inability to understand how important confounding variables such as race/ethnicity and adiposity might affect the association. Randomized controlled trial data remain limited but are critical to understanding whether supplementation with vitamin D beyond what is contained in routine prenatal vitamins will prevent GDM or improve glucose tolerance for women with GDM.

Vitamin D deficiency may be a risk factor for recurrent pregnancy losses by increasing cellular immunity and autoimmunity

STUDY QUESTION

Do women with recurrent pregnancy losses (RPL) and low vitamin D have increased prevalence of auto- and cellular immune abnormalities when compared with women with RPL who have normal vitamin D, and does vitamin D have any effect on cellular immunity in vitro?

SUMMARY ANSWER

A high proportion of women with RPL have vitamin D deficiency and the risk of auto- and cellular immune abnormalities is increased in women with RPL and vitamin D deficiency.

WHAT IS KNOWN ALREADY

Vitamin D deficiency in pregnant women is associated with increased risk of obstetrical complications such as pre-eclampsia, bacterial vaginosis associated preterm delivery, gestational diabetes mellitus and small-for-gestational age births.

STUDY DESIGN, SIZE, DURATION

A retrospective cross-sectional study of 133 women with RPL who were enrolled in a 2-year period, together with laboratory experiments.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women with three or more consecutive spontaneous abortions prior to 20 weeks of gestation who were enrolled at the University clinic. Serum vitamin D level, cellular activity and autoimmune parameters in vivo and in vitro were measured.

MAIN RESULTS AND THE ROLE OF CHANCE

Sixty-three out of 133 women (47.4%) had low vitamin D (<30 ng/ml). The prevalence of antiphospholipid antibody (APA) was significantly higher in low vitamin D group (VDlow) (39.7%) than in the normal vitamin D group (VDnl) (22.9%) (P< 0.05) and the adjusted odds ratio (OR) for APA in VDlow was 2.22 with the 95% confidence interval (CI) of 1.0-4.7. The prevalence of antinuclear antigen antibody (VDlow versus VDnl; 23.8% versus 10.0%, OR 2.81, 95% CI 1.1-7.4), anti-ssDNA (19.0% versus 5.7%, OR 3.76, 95% CI 1.1-12.4) and thyroperoxidase antibody (33.3% versus 15.7%, OR 2.68, 95% CI 1.2-6.1) was significantly higher in VDlow than those of VDnl (P < 0.05 each). Peripheral blood CD19(+) B and CD56(+) NK cell levels and NK cytotoxicity at effector to target cell (E:T) ratio of 25:1 were significantly higher in VDlow when compared with those of VDnl (P < 0.05 each). Reduction (%) of NK cytotoxicity (at E:T ratio of 50:1 and 25:1) by IgG (12.5 mg/dl) was significantly lower in VDlow than those of VDnl (P < 0.05, P < 0.01, respectively). There were no differences in Th1/Th2 ratios between VDlow and VDnl. When vitamin D3 was added in NK cytotoxicity assay in vitro, NK cytotoxicity at E:T ratio of 50:1 was significantly suppressed with 10 nMol/L (nM) (11.9 ± 3.3%) and 100 nM (10.9 ± 3.7%) of vitamin D3 when compared with controls (15.3 ± 4.7%) (P < 0.01 each). TNF-α/IL-10 expressing CD3(+)/4(+) cell ratios were significantly decreased with 100 nM of vitamin D3 (31.3 ± 9.4, P < 0.05) when compared with controls (40.4 ± 11.3) in vitro. Additionally, INF-γ/IL-10 expressing CD3(+)/4(+) cell ratio was significantly decreased with 100 nM of vitamin D3 (12.1 ± 4.0, P < 0.05) when compared with controls (14.8 ± 4.6). IFN-γ and TNF-α secretion from NK cells were significantly decreased (P < 0.01 each), and IL-10, IL-1β, vascular endothelial growth factor and granulocyte colony stimulating factor levels were significantly increased (P < 0.01 each) with vitamin D3 100 nM when compared with those of controls.

LIMITATIONS, REASONS FOR CAUTION

The prevalence of vitamin D deficiency in women with RPL in this study is open to a possible type I error since women with vitamin D supplementation were excluded from this study.

WIDER IMPLICATIONS OF THE FINDINGS

Assessment of vitamin D level is recommended in women with RPL. Vitamin D supplementation should be explored further as a possible therapeutic option for RPL.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the intramural funding from Department of Microbiology and Immunology, Chicago Medical School at Rosalind Franklin University of Medicine and Science. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Maternal serum 25-hydroxyvitamin D and placental vascular pathology in a multicenter US cohort

BACKGROUND

Maternal vitamin D deficiency has been linked to fetal growth restriction, but the underlying mechanisms are unclear.

OBJECTIVE

We tested the hypothesis that poor maternal 25-hydroxyvitamin D [25(OH)D] is associated with increased risk of placental vascular pathology.

DESIGN

Maternal serum 25(OH)D was measured at ≤26 wk of gestation in a random subcohort of term, singleton infants in the Collaborative Perinatal Project (1959-1966; n = 2048). A dichotomous vascular construct was created from the presence of any of 12 pathologies identified on placental examinations, including evidence of placental abruption, infarction, hypoxia, decidual vasculopathy, or thrombosis of fetal vessels (n = 240 cases).

RESULTS

The relation between 25(OH)D and vascular pathology was modified by infant sex (P = 0.003). A maternal 25(OH)D concentration ≥80 compared with <50 nmol/L was associated with 49% lower risk of pathology in boys [adjusted OR (95% CI): 0.27, 0.95] after conditioning on study site. No associations were observed between maternal 25(OH)D and pathology in mothers with female offspring. Subsequent analyses showed that, in pregnancies with a female fetus, vascular pathology was associated with a reduced birth-weight z score when the mother's 25(OH)D concentration was <30 nmol/L (β: -0.73; 95% CI: -1.17, -0.30). No association was observed between pathology and birth weight in mothers of female offspring with 25(OH)D concentrations ≥30 nmol/L or in boys, regardless of maternal 25(OH)D status.

CONCLUSIONS

Our findings suggest complex relations between vitamin D, placental vascular pathology, and birth weight that differ by infant sex. Maternal vitamin D status may be beneficial for male and female offspring through different mechanisms.

Health characteristics and outcomes of two randomized vitamin D supplementation trials during pregnancy: a combined analysis

OBJECTIVE

To assess the safety and health effects of vitamin D supplementation during pregnancy.

METHODS AND DESIGN

Datasets from two randomized clinical trials were first analyzed separately then combined for this analysis using a common data dictionary. In the NICHD trial, women were randomized to 400, 2000, or 4000IU vitamin D3/day, stratified by race. In the Thrasher Research Fund trial, participants were randomized to 2000 or 4000IU vitamin D3/day. Study drugs were from the same manufacturing lot for both trials. Identical questionnaires were given for comparable sociodemographics & clinical characteristics. Outcome measures were: [1] maternal and neonatal 25(OH)D achieved, and [2] maternal comorbidities of pregnancy (COP). SAS 9.3 was used for all analyses.

RESULTS

In the combined cohort, there were 110 controls, 201 in the 2000IU group, and 193 in the 4000IU group. No differences between groups in baseline 25(OH)D were found; however, delivery and cord blood values were greater in the 4000IU group (p<0.0001), an effect that persisted even after controlling for race and study. A greater percent were vitamin D replete in the 4000IU group (p<0.0001). There was a trend where the 4000IU group had decreased rates of comorbidities of pregnancy. There was a strong association between COP and final maternal 25(OH)D; an effect that persisted even after controlling for race and study (p=0.006).

CONCLUSIONS

Supplementation with 4000IU/day was associated with lower risk of hypovitaminosis D than Control and 2000IU groups. While not statistically significant, there was a trend toward lower rates of COP as supplementation dose increased. Maternal delivery 25(OH)D was inversely associated with any comorbidity of pregnancy, with fewer events as 25(OH)D increased. Future studies are needed to confirm these findings and determine the mechanisms of action of such effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Maternal 25-hydroxyvitamin d and preterm birth in twin gestations

OBJECTIVE

To assess whether there was an independent association between maternal 25-hydroxyvitamin D concentrations at 24-28 weeks of gestation and preterm birth in a multicenter U.S. cohort of twin pregnancies.

METHODS

Serum samples from women who participated in a clinical trial of 17 α-hydroxyprogesterone caproate for the prevention of preterm birth in twin gestations (2004-2006) were assayed for 25-hydroxyvitamin D concentrations using liquid chromatography tandem mass spectrometry (n=211). Gestational age was determined early in pregnancy using a rigorous algorithm. Preterm birth was defined as delivery of the first twin or death of either twin at less than 35 weeks of gestation.

RESULTS

The mean serum 25-hydroxyvitamin D concentration was 82.7 nmol/L (standard deviation 31.5); 40.3% of women had concentrations less than 75 nmol/L. Preterm birth at less than 35 weeks of gestation occurred in 49.4% of women with 25-hydroxyvitamin D concentrations less than 75 nmol/L compared with 26.2% among those with concentrations of 75 nmol/L or more (P<.001). After adjustment for maternal race and ethnicity, study site, parity, prepregnancy body mass index, season, marital status, education, gestational age at blood sampling, smoking status, and 17 α-hydroxyprogesterone caproate treatment, maternal 25-hydroxyvitamin D concentration of 75 nmol/L or more was associated with a 60% reduction in the odds of preterm birth compared with concentrations less than 75 nmol/L (adjusted odds ratio [OR] 0.4, 95% confidence interval [CI] 0.2-0.8). A similar protective association was observed when studying preterm birth at less than 32 weeks of gestation (OR 0.2, 95% CI 0.1-0.6) and after confounder adjustment.

CONCLUSIONS

Late second-trimester maternal 25-hydroxyvitamin D concentrations less than 75 nmol/L are associated with an increase in the risk of preterm birth in this cohort of twin pregnancies.

LEVEL OF EVIDENCE

II.

Cross-sectional study of factors that influence the 25-hydroxyvitamin D status in pregnant women and in cord blood in Germany

There is increasing evidence of an association between a low maternal vitamin D status and a high risk of adverse pregnancy outcomes. In a cross-sectional study, we investigated the vitamin D status of pregnant women to determine potentially influencing factors. Between December 2010 and February 2012, 261 maternal blood samples and 328 cord blood samples were collected for the analysis of 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone, alkaline phosphatase and Ca concentrations. Demographical characteristics and clinical data were recorded by a questionnaire and from medical files. The overall median maternal and cord blood 25(OH)D levels were 25·0 (interquartile range 12·6–45·5) nmol/l and 34·1 (interquartile range 17·7–58·6) nmol/l, respectively. During the winter months,98% of the maternal blood samples and 94% of the cord blood samples had 25(OH)D levels ,50 nmol/l. In the summer months, 49% of the women and 35% of the cord blood samples were vitamin D deficient. Using logistic regression models, significant risk factors for maternal vitamin D deficiency were found to be physical inactivity (adjusted OR (aOR) 2·67, 95% CI 1·06, 6·69, P=0·032) and a non-European country of origin (aOR 3·21, 95% CI 1·0, 10·28, P=0·047) after controlling for season and independent risk factors. These results are the first 25(OH)D data for pregnant women in Germany. They indicate the need for urgent implementation of strategies to prevent vitamin D deficiency by healthcare authorities that are in charge of preventing vitamin D deficiency, especially during these sensitive stages of life.

Randomized placebo-controlled trial of high-dose prenatal third-trimester vitamin D3 supplementation in Bangladesh: the AViDD trial

Background

Antenatal vitamin D status may be associated with the risk of adverse pregnancy and neonatal outcomes; however, the benefits of vitamin D supplementation during pregnancy remain unknown.

Methods

We conducted a double-blind placebo-controlled randomized trial to evaluate the effect of high-dose prenatal 3^rd trimester vitamin D3 supplementation on maternal and neonatal (cord blood) serum 25-hydroxyvitamin D (25(OH)D) concentration (primary biochemical efficacy outcome) and maternal serum calcium concentration (primary safety measure). Eligibility criteria were pregnant women aged 18 to <35 years, at 26 to 29 weeks gestation, and residing in Dhaka, Bangladesh. 160 women were randomized by 1:1 allocation to one of two parallel intervention groups; placebo (n = 80) or 35,000 IU/week of vitamin D3 (n = 80) until delivery. All participants, study personnel and study investigators were blind to treatment allocation.

Results

Mean maternal 25(OH)D concentration was similar in the vitamin D and placebo groups at baseline (45 vs. 44 nmol/L; p = 0.66), but was significantly higher in the vitamin D group vs. placebo group among mothers at delivery (134 vs. 38 nmol/L; p < 0.001) and newborns (cord blood: 103 vs. 39; p < 0.001). In the vitamin D group, 95% of neonates and 100% of mothers attained 25(OH)D >50 nmol/L, versus 21% mothers and 19% of neonates in the placebo group. No participants met criteria for hypercalcemia, there were no known supplement-related adverse events, and major pregnancy outcomes were similar between groups.

Conclusions

Antenatal 3^rd-trimester vitamin D3 supplementation (35,000 IU/week) significantly raised maternal and cord serum 25(OH)D concentrations above 50 nmol/L in almost all participants without inducing hypercalcemia or other observed safety concerns. Doses up to 35,000 IU/week may be cautiously used in further research aimed at establishing the clinical effects and safety of vitamin D3 supplementation in pregnancy.

Trial registration

This trial was registered at ClinicalTrials.gov (NCT01126528).

Maternal vitamin D status and adverse pregnancy outcomes: a systematic review and meta-analysis

OBJECTIVE

To estimate the associations between maternal vitamin D status and adverse pregnancy outcomes.

STUDY DESIGN

We searched electronic databases of the human literature in PubMed, EMBASE and the Cochrane Library up to October, 2012 using the following keywords: "vitamin D" and "status" or "deficiency" or "insufficiency" and "pregnancy". A systematic review and meta-analysis were conducted on observational studies that reported the association between maternal blood vitamin D levels and adverse pregnancy outcomes including preeclampsia, gestational diabetes mellitus (GDM), preterm birth or small-for-gestational age (SGA).

RESULTS

Twenty-four studies met the inclusion criteria. Women with circulating 25-hydroxyvitamin D [25(OH)D] level less than 50 nmol/l in pregnancy experienced an increased risk of preeclampsia [odds ratio (OR) 2.09 (95% confidence intervals 1.50-2.90)], GDM [OR 1.38 (1.12-1.70)], preterm birth [OR 1.58 (1.08-2.31)] and SGA [OR 1.52 (1.08-2.15)].

CONCLUSION

Low maternal vitamin D levels in pregnancy may be associated with an increased risk of preeclampsia, GDM, preterm birth and SGA.

Predisease conditions and serum vitamin D levels in healthy Mexican American adults

AIMS

To elucidate the relationship between low circulating serum vitamin D levels and predisease conditions (ie, prediabetes and prehypertension) in healthy Mexican American adults.

METHODS

Analyses were conducted using data from the United States National Health and Nutrition Examination Survey (NHANES) from 2001 through 2006. Free-living (ie, community-dwelling, nonimprisoned) adult Mexican American subjects (N = 788; men, n = 443; women, n = 345) who had provided written informed consent and had no history of diabetes, hypertension, dyslipidemia, metabolic syndrome, and/or cardiovascular disease were included in this report. Participants were not ingesting any prescription medications, nor did they exhibit any evidence of malabsorption. Participants were determined to be disease free.

RESULTS

The mean serum vitamin D level for Mexican American adults (N = 788) of 50.5 nmol/L was significantly higher (P < 0.0001) than the mean of 35.9 nmol/L for non-Hispanic black adults (n = 621), and significantly lower (P < 0.0001) than the mean of 65.0 nmol/L for non-Hispanic white adults (n = 1711). Although age, sex, and body mass index were all significantly associated with prehypertension and prediabetes, no such association was found for serum vitamin D levels.

CONCLUSION

A successive, incremental shift of approximately 15 nmol/L in vitamin D distribution was seen in the transition from the dark-skinned non-Hispanic black population to the brown-skinned Mexican American population, and from the brown-skinned Mexican American population to the non-Hispanic white population. In contrast to the non-Hispanic black and non-Hispanic white populations, wherein previous studies found that serum vitamin D levels below the 75th percentile were associated with prediabetes and prehypertension, no such association was detected among the Mexican American population. The reason for this lack of association among the Mexican American population is unclear.

A randomized trial of vitamin D supplementation in 2 community health center networks in South Carolina

OBJECTIVE

We sought to determine whether 4000 IU/d (vs 2000 IU/d) of vitamin D during pregnancy is safe and improves maternal/neonatal 25-hydroxyvitamin D [25(OH)D] in a dose-dependent manner.

STUDY DESIGN

A total of 257 pregnant women 12-16 weeks' gestation were enrolled. Randomization to 2000 vs 4000 IU/d followed 1-month run-in at 2000 IU/d. Participants were monitored for hypercalciuria, hypercalcemia, and 25(OH)D status.

RESULTS

Maternal 25(OH)D (n = 161) increased from 22.7 ng/mL (SD 9.7) at baseline to 36.2 ng/mL (SD 15) and 37.9 ng/mL (SD 13.5) in the 2000 and 4000 IU groups, respectively. While maternal 25(OH)D change from baseline did not differ between groups, 25(OH)D monthly increase differed between groups (P < .01). No supplementation-related adverse events occurred. Mean cord blood 25(OH)D was 22.1 ± 10.3 ng/mL in 2000 IU and 27.0 ± 13.3 ng/mL in 4000 IU groups (P = .024). After controlling for race and study site, preterm birth and labor were inversely associated with predelivery and mean 25(OH)D, but not baseline 25(OH)D.

CONCLUSION

Maternal supplementation with vitamin D 2000 and 4000 IU/d during pregnancy improved maternal/neonatal vitamin D status. Evidence of risk reduction in infection, preterm labor, and preterm birth was suggestive, requiring additional studies powered for these endpoints.

Development and validation of a vitamin D status prediction model in Danish pregnant women: a study of the Danish National Birth Cohort

Vitamin D has been hypothesized to reduce risk of pregnancy complications such as preeclampsia, gestational diabetes mellitus, and preterm delivery. However, many of these outcomes are rare and require a large sample size to study, representing a challenge for cohorts with a limited number of preserved samples. The aims of this study were to (1) identify predictors of serum 25-hydroxy-vitamin D (25(OH)D) among pregnant women in a subsample (N = 1494) of the Danish National Birth Cohort (DNBC) and (2) develop and validate a score predicting 25(OH)D-status in order to explore associations between vitamin D and maternal and offspring health outcomes in the DNBC. In our study sample, 42.3% of the population had deficient levels of vitamin D (<50 nmol/L 25(OH)D) and average levels of 25(OH)D-status were 56.7(s.d. 24.6) nmol/L. A prediction model consisting of intake of vitamin D from diet and supplements, outdoor physical activity, tanning bed use, smoking, and month of blood draw explained 40.1% of the variance in 25(OH)D and mean measured 25(OH)D-level increased linearly by decile of predicted 25(OH)D-score. In total 32.2% of the women were placed in the same quintile by both measured and predicted 25(OH)D-values and 69.9% were placed in the same or adjacent quintile by both methods. Cohen's weighted kappa coefficient (Κ = 0.3) reflected fair agreement between measured 25(OH)D-levels and predicted 25(OH)D-score. These results are comparable to other settings in which vitamin D scores have shown similar associations with disease outcomes as measured 25(OH)D-levels. Our findings suggest that predicted 25(OH)D-scores may be a useful alternative to measured 25(OH)D for examining associations between vitamin D and disease outcomes in the DNBC cohort, but cannot substitute for measured 25(OH)D-levels for estimates of prevalence.

Maternal serum 25-hydroxyvitamin D and measures of newborn and placental weight in a U.S. multicenter cohort study

CONTEXT

Inconsistent associations between maternal vitamin D status and fetal size have been published in small studies.

OBJECTIVE

Our objective was to examine the association between maternal 25-hydroxyvitamin D [25(OH)D] levels and measures of newborn and placental weight.

DESIGN AND SETTING

We measured maternal 25(OH)D in mothers from the Collaborative Perinatal Project, an observational cohort conducted in 12 U.S. medical centers from 1959 to 1965.

PARTICIPANTS

Women delivering singleton, term, live births with 25(OH)D measured at a gestation of 26 wk or less (n = 2146).

MAIN OUTCOME MEASURES

Birth weight, ponderal index, placental weight, the placental to fetal weight ratio, and small for gestational age were measured. Hypotheses were formulated after data collection.

RESULTS

After confounder adjustment, mothers with 25(OH)D of 37.5 nmol/liter or greater gave birth to newborns with 46 g [95% confidence interval (CI), 9-82 g] higher birth weights and 0.13 cm (0.01-0.25 cm) larger head circumferences compared with mothers with less than 37.5 nmol/liter. Birth weight and head circumference rose with increasing 25(OH)D up to 37.5 nmol/liter and then leveled off (P < 0.05). No association was observed between 25(OH)D and ponderal index, placental weight, or the placental to fetal weight ratio. Maternal 25(OH)D of 37.5 nmol/liter or greater vs. less than 37.5 nmol/liter in the first trimester was associated with half the risk of small for gestational age (adjusted odds ratio 0.5; 95% CI 0.3-0.9), but no second-trimester association was observed.

CONCLUSIONS

Maternal vitamin D status is independently associated with markers of physiological and pathological growth in term infants. Adequately powered randomized controlled trials are needed to test whether maternal vitamin D supplementation may improve fetal growth.

Variation in vitamin D supplementation among adults in a multi-race/ethnic health plan population, 2008

Background

Vitamin D may have a role in many chronic conditions in addition to bone health. Nutritional surveys among Americans have reported high levels of vitamin D insufficiency, especially among Blacks and Latinos. Our study examined variation in vitamin D supplementation practices in an adult health plan population by age, gender, and race-ethnicity.

Methods

Self-report data from a 2008 general health survey in a large Northern California health plan were used to characterize number and types of sources of vitamin D supplementation (multivitamin, calcium with D, singular D) among women and men aged 25-85, overall, by race-ethnicity, and for obese, diabetic, and hypertensive subgroups.

Results

In this population, 40% of women and 54% of men ≤ 50, and 24% of women and 53% of men aged 51-85 get no vitamin D from dietary supplements. Higher vitamin D supplementation among women > 50 is associated with higher reported intake of calcium with D. Black and Latina women aged 25-85 and Filipinas in the ≤ 50 age group were significantly less likely than non-Hispanic Whites to get vitamin D from supplements, whereas vitamin D supplementation practices among Chinese women did not significantly differ from non-Hispanic Whites. Among men, Latinos aged 25-85 and Black and Chinese ≤ 50 were significantly less likely than non-Hispanic Whites to get vitamin D from supplements. Similar race-ethnic differences in vitamin D supplementation patterns were observed for people in the obese, diabetic, and hypertensive groups.

Conclusions

Our survey results suggest that in 2008, a large percentage of women and an even larger percentage of men in a large Northern California health plan get no vitamin D from dietary supplements, and that Blacks and Latinos and obese adults, who are at higher risk of vitamin D deficiency, are also the least likely to get any vitamin D from dietary supplements.

Low vitamin D levels, prediabetes and prehypertension in healthy African American adults

AIMS

To determine if customary lower serum vitamin D concentrations in healthy African American (AA) adults are associated with modest elevations in fasting plasma glucose (FPG) and/or resting blood pressure (BP). Numerous health disparities between African American (AA) and Caucasian American (CA) adults, especially those which increase cardiovascular morbidity and mortality, have been attributed to lower serum vitamin D concentrations in the AA. Prediabetes (PreDM) and prehypertension (PreHTN) are significantly more prevalent in healthy disease free CA adults with serum vitamin D concentrations below the 75th percentile for the Caucasian cohort. We hypothesized that despite overall lower serum vitamin D concentrations in AA, an increase in the prevalence for PreDM and PreHTN would be seen in those with low vitamin D levels.

METHODS AND RESULTS

Disease free AA adults in the National Health and Nutrition Examination Survey 2001-2006 were assessed. PreDM and PreHTN were diagnosed using the ADA and JNC 7 criteria: (FPG) 100-125 mg/dL and resting systolic (SBP) 120-139 and/or diastolic (DBP) 80-89 mm Hg, respectively. Logistic regression was employed to assess effects of low vitamin D concentrations on the odds for PreDM and PreHTN (n = 621). Age, gender and BMI adjusted odds ratio for co-morbid PreDM and PreHTN in AA men (n = 343) and women (n = 278) with vitamin D levels ≤45.4 versus >45.4 nmol/L was 2.02 (1.11, 3.68), (p < 0.021).

CONCLUSIONS

Evaluating serum vitamin D levels, with consideration for supplementation in seemingly healthy AA adults with prediabetes, prehypertension, or co-existing prediabetes and prehypertension, has merit.

Neighborhood poverty, park use, and park-based physical activity in a Southern California city

A rich literature indicates that individuals of lower socio-economic status engage in less leisure time physical activity than individuals of higher socio-economic status. However, the source of the difference is believed to be, in part, due to differential access to resources that support physical activity. However, it has not been shown as to whether equal access to parks can mitigate differences in leisure time physical activity. Using systematic direct observation, we quantified physical activity in neighborhood parks in a large Southern California city located in areas with high, medium, and a low percentage of households in poverty. We documented how neighborhood parks are managed and programmed and also interviewed both a sample of park users and a random sample of households within a mile radius of the parks. We found that parks are used less in high-poverty areas compared to medium- and low-poverty area parks, even after accounting for differences in size, staffing, and programming. The strongest correlates of park use were the number of part time staff, the number of supervised and organized programs, and knowing the park staff. Perceptions of safety were not relevant to park use among those interviewed in the park, however it had a small relationship with reported frequency of park use among local residents. Among park users, time spent watching electronic media was negatively correlated with the frequency of visiting the park. Future research should test whether increasing park staffing and programming will lead to increased park use in high-poverty neighborhoods.

The role of vitamin D in pregnancy and lactation: emerging concepts

Pregnancy is a critical time in the lifecycle of a woman where she is responsible not only for her own well-being, but also that of her developing fetus, a process that continues during lactation. Until recently, the impact of vitamin D status during this period had not been fully appreciated. Data regarding the importance of vitamin D in health have emerged to challenge traditional dogma, and suggest that vitamin D - through its effect on immune function and surveillance - plays a role beyond calcium and bone metabolism on the health status of both the mother and her fetus. Following birth, this process persists; the lactating mother continues to be the main source of vitamin D for her infant. Thus, during both pregnancy and lactation, maternal deficiency predicts fetal and infant deficiency; the significance of this is just beginning to be understood and will be highlighted in this review.

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

Vitamin D has well-defined classical functions related to calcium metabolism and bone health but also has non-classical effects that may influence other aspects of health. There has been considerable recent interest in the role of vitamin D on outcomes related to pregnancy and young child health but few efforts have been made to systematically consolidate this evidence to inform the research and policy agenda for low-income countries. A systematic review was undertaken to identify intervention and observational studies of vitamin D supplementation, intake or status (25-hydroxy-vitamin D) during pregnancy on perinatal and infant health outcomes. Data from trials and observational studies isolating the effect of vitamin D supplementation and intake were extracted and study quality was evaluated. Meta-analysis was used to pool effect estimates. We identified five randomised trials with outcomes of relevance to our review. All had small sample size and dosage amount, duration and frequency varied as did the ability to correct deficiency. Pooled analysis of trials using fixed-effects models suggested protective effects of supplementation on low birthweight (three trials, risk ratio (RR) = 0.40 [95% confidence interval (CI) 0.23, 0.71]) and non-significant but suggestive effects of daily supplementation on small-for-gestational age (two trials, RR = 0.67 [0.40, 1.11]). No effect on preterm delivery (<37 weeks) was evident (two trials, RR = 0.77 [0.35, 1.66]). Little evidence from trials exists to evaluate the effect of vitamin D supplementation during pregnancy on maternal, perinatal or infant health outcomes. Based on both trials and observational studies, we recommend that future research explore small-for-gestational age, preterm delivery, pre-eclampsia, and maternal and childhood infections, as outcomes of interest. Trials should focus on populations with a high prevalence of vitamin D deficiency, explore the relevance of timing of supplementation, and the dosage used in such trials should be sufficient to correct deficiency.

Low fish intake is associated with low blood concentrations of vitamin D, choline and n-3 DHA in pregnant women

Several studies have investigated the potential health benefits, including those associated with neurological function, of the n-3 fatty acid DHA. This has arisen in part because of the association between higher intakes of fish, which is a major dietary source of DHA, and reduced disease risk. In addition to DHA, fish also provides choline and vitamin D. The objective of the present study was to assess whether women in the first half of pregnancy with low fish intake also had low blood concentrations of vitamin D, choline and DHA. A total of 222 pregnant women at 16 weeks of gestation were examined for dietary intake, erythrocyte (phosphatidylethanolamine PE) DHA, plasma free choline and 25-hydroxyvitamin D (25(OH)D). Women who consumed ≤ 75 g fish/week (n 56) compared to ≥ 150 g fish/week (n 116) had lower dietary intake of DHA, total choline and vitamin D (P< 0·001), and lower erythrocyte PE DHA (5·25 (sd 1·27), 6·83 (sd 1·62) g/100 g total fatty acid, respectively, P< 0·01), plasma free choline (6·59 (sd 1·65), 7·40 (sd 2·05) μmol/l, respectively, P= 0·023) and 25(OH)D (50·3 (sd 20·0), 62·5 (sd 29·8) nmol/l, respectively, P< 0·01). DHA intake was positively related to the intake of vitamin D from foods (ρ 0·47, P< 0·001) and total choline (ρ 0·32, P< 0·001). Dietary intakes and biomarkers of DHA, choline and vitamin D status were assessed to be linked. This raises the possibility that unidentified concurrent nutrient inadequacies might have an impact on the results of studies addressing the benefits of supplemental DHA.

Plasma 25-hydroxyvitamin D during pregnancy and small-for-gestational age in black and white infants

PURPOSE

In a prospective prenatal cohort study, we examined associations of second trimester and cord plasma 25-hydroxyvitamin D (25[OH]D) with small-for-gestational age (SGA) and the extent to which vitamin D might explain black/white differences in SGA.

METHODS

We studied 1067 white and 236 black mother-infant pairs recruited from eight obstetrical offices early in pregnancy in Massachusetts. We analyzed 25(OH)D levels using an immunoassay and performed multivariable logistic models to estimate the odds of SGA by category of 25(OH)D level.

RESULTS

Mean (SD) second trimester 25(OH)D level was 60 nmol/L (SD, 21) and was lower for black (46 nmol/L [SD, 22]) than white (62 nmol/L [SD, 20]) women. Fifty-nine infants were SGA (4.5%), and more black than white infants were SGA (8.5% vs. 3.7%). The odds of SGA were higher with maternal 25(OH)D levels less than 25 versus 25 nmol/L or greater (adjusted odds ratio, 3.17; 95% confidence interval, 1.16-8.63). The increased odds of SGA among black versus white participants decreased from an odds ratio of 2.04(1.04, 4.04) to 1.68(0.82, 3.46) after adjusting for 25(OH)D.

CONCLUSIONS

Second trimester 25(OH)D levels less than 25 nmol/L were associated with higher odds of SGA. Our data raise the possibility that vitamin D status may contribute to racial disparities in SGA.

Maternal micronutrient status and preterm versus term birth for black and white US women

OBJECTIVE

Micronutrient deficiencies are hypothesized to play a role in spontaneous preterm birth (PTB; <37 weeks of gestation) and possibly the racial disparity in rates of PTB between black and white women. Yet relatively few studies have addressed the role of micronutrient deficiencies in spontaneous PTB among black and white women in the United States. The purpose of this study was to investigate whether 25-hydroxy vitamin D (25-OH-D), folate, and omega-6/omega-3 fatty acid status are associated with spontaneous PTB among black and white women in the United States.

METHODS

Biospecimens and medical record data for this study were derived from a subsample of the 1547 women enrolled into the Nashville Birth Cohort during 2003-2006. We randomly selected 80 nulliparous and primiparous women for whom stored plasma samples from the delivery admission were available and analyzed the stored plasma for 25-OH-D, folate, and total omega-6/omega-3 fatty acids. We used multivariate logistic regression to assess the odds of spontaneous PTB among women with 25-OH-D <20 ng/mL, folate <5 ug/L, and omega-6/omega-3 >15.

RESULTS

An omega-6/omega-3 ratio >15 was significantly associated with spontaneous PTB for white (adjusted odds ratio [aOR] 4.25, 95% confidence interval [CI] 1.25-14.49) but not black women (aOR 1.90, 95% CI: 0.69-5.40), whereas no significant relationships were observed for folate and 25-OH-D status and PTB for black or white women.

CONCLUSION

Maternal plasma total omega-6/omega-3 fatty acid ratio >15 at delivery was significantly associated with spontaneous PTB for white, but not black, women.

Sources and determinants of vitamin D intake in Danish pregnant women

Vitamin D deficiency during pregnancy has been associated with the development of several adverse health outcomes, e.g., pre-eclampsia, gestational diabetes mellitus, preterm delivery, low birth weight, birth length, and bone mineral content. The aims of the present study were to estimate the intake and sources of vitamin D in Danish pregnant women and to examine potential determinants of vitamin D intake of the recommended level (10 µg per day). In 68,447 Danish pregnant women the mean ± SD for vitamin D intake was 9.23 ± 5.60 µg per day (diet: 3.56 ± 2.05 µg per day, supplements: 5.67 ± 5.20 µg per day). 67.6% of the women reported use of vitamin D supplements but only 36.9% reported use of vitamin D supplements of at least 10 µg. Supplements were the primary source of vitamin D for the two higher quartiles of total vitamin D intake, with diet being the primary source for the two lower quartiles. Determinants of sufficient total vitamin D intake were: high maternal age, nulliparity, non-smoking, and filling out of the Food Frequency Questionnaire (FFQ) during summer or fall. We propose that clinicians encourage vitamin D supplementation among pregnant women, with special focus on vulnerable groups such as the young, smokers and multiparous women, in order to improve maternal and fetal health both during and after pregnancy.

Longitudinal vitamin D status in pregnancy and the risk of pre-eclampsia

OBJECTIVE

Whether vitamin D deficiency in pregnancy is a cause of pre-eclampsia remains controversial. Most previous studies to date have assessed exposure at only one time-point in pregnancy. We assessed longitudinal vitamin D status during pregnancy and the risk of pre-eclampsia.

DESIGN

Prospective cohort study.

SETTING

Seventeen urban obstetric hospitals, Canada.

POPULATION

Pregnant women who were participants in a trial of vitamin C and E supplementation for the prevention of pre-eclampsia. Canadian participants who consented to participate in a biobank with plasma specimens available at the baseline visit were included (n = 697).

METHODS

Maternal plasma 25-hydroxyvitamin D (25(OH)D) concentrations were measured at 12-18 and 24-26 weeks of gestation using chemiluminescence immunoassay.

MAIN OUTCOME MEASURES

Pre-eclampsia.

RESULTS

Of the women, 39% were vitamin D deficient (25(OH)D <50 nmol/l). A strong positive correlation was observed in maternal 25(OH)D concentrations between the two gestational age windows (r = 0.69, P < 0.0001). Mean maternal 25(OH)D concentrations at 24-26 weeks of gestation were significantly lower in women who subsequently developed pre-eclampsia compared with those who did not (mean ± SD: 48.9 ± 16.8 versus 57.0 ± 19.1 nmol/l, P = 0.03). Women with 25(OH)D < 50 nmol/l at 24-26 weeks gestation experienced an increased risk of pre-eclampsia (adjusted odds ratio 3.24, 95% confidence interval 1.37-7.69), whereas the association was not statistically significant for maternal 25(OH)D level at 12-18 weeks of gestation.

CONCLUSIONS

Lower maternal 25(OH)D levels at late mid-trimester were associated with an increased risk of pre-eclampsia.

Factors Associated with Vitamin D Deficiency and Inadequacy among Women of Childbearing Age in the United States

Objective. To examine the prevalence and correlates of vitamin D deficiency and inadequacy among US women of childbearing age. Methods. Data from 1,814 female participants (20-44 y) in the 2003-2006 NHANES were analyzed to estimate the age-adjusted prevalence and prevalence ratios with 95% confidence intervals (CIs) for vitamin D deficiency (defined as serum 25-hydroxyvitamin D [25(OH)D] <12.0 ng/mL) and inadequacy (defined as 25(OH)D: 12.0-<20.0 ng/mL). Results. The age-adjusted prevalence was 11.1% (95% CI: 8.8-14.0%) for vitamin D deficiency and 25.7% (95% CI: 22.3-29.5%) for vitamin D inadequacy. Race/ethnicity other than non-Hispanic white and obesity were associated with increased risks, whereas dietary supplement use, milk consumption of ≥1 time/day, and potential sunlight exposure during May-October were associated with decreased risks for both vitamin D deficiency and inadequacy (P < 0.05). Current smoking and having histories of diabetes and cardiovascular disease were also associated with an increased risk for vitamin D deficiency (P < 0.05). Conclusions. Among women of childbearing age, periconceptional intervention programs may focus on multiple risk factors for vitamin D deficiency and inadequacy to ultimately improve their vitamin D nutrition.

Vitamin D and its role during pregnancy in attaining optimal health of mother and fetus

Despite its discovery a hundred years ago, vitamin D has emerged as one of the most controversial nutrients and prohormones of the 21st century. Its role in calcium metabolism and bone health is undisputed but its role in immune function and long-term health is debated. There are clear indicators from in vitro and animal in vivo studies that point to vitamin D's indisputable role in both innate and adaptive immunity; however, the translation of these findings to clinical practice, including the care of the pregnant woman, has not occurred. Until recently, there has been a paucity of data from randomized controlled trials to establish clear cut beneficial effects of vitamin D supplementation during pregnancy. An overview of vitamin metabolism, states of deficiency, and the results of recent clinical trials conducted in the U.S. are presented with an emphasis on what is known and what questions remain to be answered.

Suboptimal maternal vitamin D status and low education level as determinants of small-for-gestational-age birth weight

PURPOSE

This study aimed firstly to investigate the contribution of maternal 25(OH) vitamin D to the association of maternal education and small-for-gestational-age birth weight (SGA) and secondly to examine whether the contribution of 25(OH) vitamin D differs by overweight, season, and maternal smoking.

METHODS

Logistic regression analysis was carried out in this study, using data of 2,274 pregnant women of Dutch ethnicity from the ABCD study, a population-based cohort study in the Netherlands. Maternal 25(OH) vitamin D was measured in early pregnancy. Stratified analyses were conducted for overweight, season of blood sampling, and smoking.

RESULTS

Low-educated women had lower 25(OH) vitamin D levels compared to high-educated women, and women in the lowest 25(OH) vitamin D quartile had a higher risk of SGA offspring. In addition, low-educated women had a higher risk of SGA offspring (OR 1.95 [95% CI: 1.20-3.14]). This association decreased with 7% after adjustment for 25(OH) vitamin D (OR 1.88 [95% CI 1.16-3.04]). In stratified analyses, adjustment for 25(OH) vitamin D resulted in a decrease in OR of about 17% in overweight women and about 15% in women who conceived in wintertime.

CONCLUSIONS

25(OH) vitamin D appears to be a modifiable contributor to the association between low maternal education and SGA offspring, particularly in overweight women and women who conceived in the winter period. In those women, increasing the intake of vitamin D, either through dietary adaptation or through supplementation in order to achieve the recommendation, could be beneficial.

Biomarkers of spontaneous preterm birth: an overview of the literature in the last four decades

BACKGROUND

Understanding spontaneous preterm birth ([PTB] < 37 weeks) is difficult due to heterogeneities associated with multitudes of risk factors and pathophysiological pathways. Several biomarkers are routinely used clinically for predicting preterm labor; however, these factors are either nonspecific or detected too late.

OBJECTIVE

Systematic review of literature on PTB biomarkers in the last 40 years to map out the existing knowledge and gaps in understanding PTB biomarkers.

SEARCH STRATEGIES

Five electronic databases were searched for human studies on PTB biomarkers published in any language between 1965 and 2008.

SELECTION CRITERIA

The phenotype of interest for final data extraction was exclusively spontaneous PTB with no rupture of membranes. Data extraction included (a) general characteristics of the study (clinical setting, period, and study design), (b) study/participant characteristics (inclusion and exclusion criteria, race/ethnicity, number of participants, gestational age at sampling, (c) characteristics of the biomarker (type, rationale for its selection, type of biological sample, and assay used, and (d) concentration of biomarkers in cases and controls.

DATA COLLECTION AND ANALYSIS

The search yielded 7255 citations and data were extracted from 217 articles which met our inclusion and exclusion criteria.

MAIN RESULTS

A total of 116 different biomarkers were reported and these were assayed 578 times in the 217 included studies. Over two thirds of the 217 studies were performed on North American or European populations. No reliable biomarkers emerged as a risk predictor of PTB.

CONCLUSIONS

Identifying similar studies on biomarkers for the prediction of PTB was a very challenging task due heterogeneities in study design, sampling issues (types, timing and processing), assay methods, and analyses. Major areas of concern identified in this review include poor phenotype definition, nonideal study designs and poor rationale for biomarker selection and assays and population stratification issues.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A nested case-control study of first-trimester maternal vitamin D status and risk for spontaneous preterm birth

We assessed if first-trimester vitamin D deficiency is more prevalent in women who experienced a spontaneous preterm birth compared with women who delivered at term. We conducted a nested case-control study of pregnant women who had previously given blood for first-trimester combined screening for trisomy 21 and subsequently delivered at a tertiary hospital between November 2004 and July 2009. From an overall cohort of 4225 women, 40 cases of spontaneous preterm birth (≥ 23 (0/7) and ≤ 34 (6/7) weeks) were matched by race/ethnicity with 120 women delivering at term (≥ 37 (0/7) weeks) with uncomplicated pregnancies. Banked maternal serum was used to measure maternal 25-hydroxyvitamin D [25(OH)D]. The prevalence of first-trimester maternal vitamin D deficiency [25(OH)D < 50 nmol/L] was comparable among women who subsequently delivered preterm compared with controls (7.5% versus 6.7%, P  = 0.90). The median 25(OH)D level for all subjects was 89 nmol/L (interquartile range, 73 to 106 nmol/L). Seventy-three percent (117/160) of the cohort had sufficient vitamin D levels [25(OH)D ≥ 75 nmol/L]. In a cohort of pregnant women with mostly sufficient levels of first-trimester serum 25(OH)D, vitamin D deficiency was not associated with spontaneous preterm birth.

Maternal vitamin D during pregnancy and its relation to immune-mediated diseases in the offspring

Vitamin D deficiency during pregnancy is fairly common in many parts of the world. However, currently there is no consensus on the optimal vitamin D intake during pregnancy. Vitamin D is known to be of great importance for the homeostatic functions within the immune system. Maternal vitamin D status during pregnancy may therefore affect the developing immune system of the fetus, thus contributing to the later development of immune-mediated diseases. This chapter introduces the basics of vitamin D during pregnancy and discusses the role of maternal vitamin D intake in the development of asthma, allergic diseases, autoimmune diseases, cancer, and infections in the offspring. So far, the strongest observational evidence underlines the potential of maternal vitamin D intake during pregnancy to influence the likelihood of asthma and allergic outcomes in the offspring. Somewhat conflicting findings imply that there might be critical time windows of exposure to adequate vitamin D levels during pregnancy. More research is needed in order to fully understand the contribution of maternal vitamin D status during pregnancy to the progress of immune-mediated diseases.

Vitamin D supplementation during pregnancy: safety considerations in the design and interpretation of clinical trials

Maternal-child health benefits of optimizing vitamin D status during pregnancy may include a reduced risk of pre-eclampsia, improved fetal growth and beneficial effects on infant immune function. These hypotheses require evaluation by randomized controlled antenatal vitamin D supplementation trials using doses that are high enough to elevate serum 25-hydroxyvitamin D concentrations into the range believed to be associated with improved health outcomes. Such doses may be considerably higher than the current recommended dietary allowance (600 IU day(-1)) or standard prenatal supplement dose (400 IU day(-1)), and may even be higher than the tolerable upper intake level (4000 IU day(-1)) advised by the Institute of Medicine (2010). A critical review of the published literature yielded limited data regarding the safety of antenatal vitamin D regimens. There have been no published reports of the teratogenic effects of vitamin D on humans. Some animal studies have suggested the potential for dose-dependent fetal toxicities (for example, growth impairment, skeletal malformations and cardiovascular anomalies), but the relevance of these observations to humans is unknown. Antenatal vitamin D supplementation trials should incorporate a range of methods for objectively establishing maternal and fetal safety, and aim to identify the lowest doses of vitamin D required to achieve target outcomes.

Prevalence of autism according to maternal immigrant status and ethnic origin

OBJECTIVE

To examine the rates of autism separately according to maternal immigrant status and ethnic origin in respect to the vitamin D insufficiency hypothesis.

METHOD

Articles were identified by electronic searches. Studies were selected when they analysed autism rates according to maternal immigrant status and/or ethnic origin using multivariate techniques.

RESULTS

This review gave further support to the association between maternal immigrant status and an increased risk of autism. The relationship with ethnic origin was more complex. Although the crude rates did not differ, multivariate analyses taking into account confounding factors found that black ethnicity was associated with an increased risk for autism. The risk was highly significant when considering the strict definition of autistic disorders as opposed to the large definition of other pervasive developmental disorders. The risk was also very significant for autism associated with mental retardation.

CONCLUSION

These results are consistent with the maternal vitamin D insufficiency hypothesis. Neurobiological studies are warranted to document the effect of maternal vitamin D insufficiency during pregnancy on the foetal brain and the window of vulnerability. This review stresses the importance of monitoring vitamin D levels in pregnant women, especially those who are immigrant, dark-skinned or veiled, and the urgency of randomized controlled trials.