Calcium and Vitamin D Supplementation for Prevention of Preeclampsia: A Systematic Review and Network Meta-Analysis

Vitamin D supplementation to improve pregnancy and perinatal outcomes: an overview of 42 systematic reviews

OBJECTIVE

To review the evidence to assess effectiveness of vitamin D supplementation during pregnancy and associations of serum vitamin D levels with perinatal outcomes.

DESIGN

Overview of systematic reviews (SRs).

DATA SOURCES

Searches conducted in January 2019: Ovid Medline (1946-), Cochrane Library databases.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Two reviewers independently screened titles and abstracts, and full texts using predefined inclusion criteria: SRs evaluating vitamin D supplementation in pregnant women and/or examining the association between serum vitamin D levels reporting at least one predefined perinatal outcome. Only SRs with high AMSTAR scores were analysed.

DATA EXTRACTION AND SYNTHESIS

Data were extracted independently by one reviewer and checked by a second. Results were assessed for quality independently by two reviewers using GRADE criteria.

RESULTS

Thirteen SRs were included, synthesising evidence from 204 unique primary studies. SRs of randomised controlled trials (RCTs) with the highest level of evidence showed no significant benefit from vitamin D in terms of preterm birth (RR 1.00 (95% CI 0.77, 1.30); high quality), pre-eclampsia (RR 0.91 (0.45, 1.86); low quality), gestational diabetes (RR 0.65 (0.39, 1.08); very low quality), stillbirth (RR 0.75 (0.50, 1.12); high quality), low birth weight (RR 0.74 (0.47, 1.16); low quality), caesarean section (RR 1.02 (0.93, 1.12); high quality). A significant difference was found for small for gestational age (RR 0.72 (0.52, 0.99); low quality). SRs of observational studies showed associations between vitamin D levels and preterm birth (RR 1.19 (1.08, 1.31); moderate quality), pre-eclampsia (RR 1.57 (1.21, 2.03) for 25-hydroxy vitamin D (25 (OH)D)<50 nmol/L subgroup; low quality), gestational diabetes (RR 1.12 (1.02, 1.22) for 25 (OH)D<50 nmol/L and RR 1.09 (1.03, 1.15)<75 nmol/L; moderate quality) and small for gestational age (RR 1.35 (1.18, 1.54)<50 nmol/L; low quality). SRs showed mixed results for associations between vitamin D and low birth weight (very low quality) and caesarean section (very low quality).

CONCLUSION

There is some evidence from SRs of observational studies for associations between vitamin D serum levels and some outcomes; however SRs examining effectiveness from RCTs showed no effect of vitamin D supplementation in pregnancy with the exception of one predefined outcome, which had low quality evidence. Credibility of the evidence in this field is compromised by study limitations (in particular, the possibility of confounding among observational studies), inconsistency, imprecision and potential for reporting and publication biases.

Evaluation of questionnaire as an instrument to measure the level of nutritional and weight gain knowledge in pregnant women in Poland. A pilot study

Pregnancy is a period in life in which women are willing to improve their lifestyle. Providing proper information for these women is crucial for their health and the health of their offspring. Clear information about weak points in their nutritional and weight gain knowledge is the first step for proper health care assistance. There are a few previous studies evaluating the nutritional and weight gain knowledge of pregnant women. In the few studies available, different approaches were taken and there was no wider discussion on the content of the questionnaires attempting to measure level of knowledge. The aim of this study, designed in a pilot fashion, was to test the adequacy of the questionnaire as a research instrument in a group of 139 pregnant Polish women. The developed instrument is a 33-item questionnaire comprising four domains: weight gain, importance of nutrients, quality and quantity of food intake. The results of this study indicate that the questionnaire is stable and internal consistency is acceptable (Cronbach’s alpha > 0.7) for dimensions with more than four items. For dimensions with less than four items, internal consistency was poor (Cronbach’s alpha < 0.7). The cumulative explained variance for domains weight gain, importance of nutrients, quantity and quality of food intake was 54.74%, 42.74%, 54.42% and 48.99% respectively. Results from validity, reliability and factor analysis indicate that the questionnaire is adequate for its purpose.

Sodium Intake during Pregnancy, but Not Other Diet Recommendations Aimed at Preventing Cardiovascular Disease, Is Positively Related to Risk of Hypertensive Disorders of Pregnancy

BACKGROUND

The role of diet on hypertensive disorders of pregnancy (HDPs), including preeclampsia and gestational hypertension (GHTN), remains unclear.

OBJECTIVES

We evaluated whether adherence during pregnancy to dietary recommendations that reduce cardiovascular disease (CVD) in the general population is related to the risk of HDPs.

METHODS

We followed 66,651 singleton pregnancies from 62,774 women participating in the Danish National Birth Cohort. Diet was assessed during week of gestation 25 with an FFQ from which we created 2 dietary pattern scores: 1) AHA, based on the diet recommendations from the AHA 2020 Strategic Impact Goals; and 2) the Dietary Approaches to Stop Hypertension (DASH) diet. Cases of HDPs were identified through linkage with the Danish National Patient Registry. RRs and 95% CIs of HDPs were estimated by increasing quintiles of adherence to the AHA and DASH scores using log-Poisson regression models with generalized estimating equations-to account for repeated pregnancies per woman-while adjusting for potential confounders.

RESULTS

We identified 1809 cases of HDPs: n = 1310 preeclampsia (n = 300 severe preeclampsia) and n = 499 cases of GHTN. Greater adherence to AHA or DASH scores was not related to the risk of HDPs. However, when each component of the scores was separately evaluated, there were positive linear relations of sodium intake with HDPs (P-linearity < 0.01). Women with the highest sodium intake [median 3.70 g/d (range: 3.52, 7.52 g/d)] had 54% (95% CI:16%, 104%) higher risk of GHTN and 20% (95% CI:1%, 42%) higher risk of preeclampsia than women with the lowest intake [median 2.60 g/d (range: 0.83, 2.79 g/d)]. In addition, intake of whole grains was positively related to the risk of GHTN but not to preeclampsia ( P-heterogeneity = 0.002).

CONCLUSION

Sodium intake during pregnancy, but no other diet recommendations to prevent CVD among nonpregnant adults, is positively related to the occurrence of HDPs among pregnant Danish women.

Maternal plasma proteomics in a rat model of pregnancy complications reveals immune and pro-coagulant gene pathway activation

PROBLEM

The Brown Norway (BN) rat is a model of T-helper 2 immune diseases, and also a model of pregnancy disorders that include placental insufficiency, fetal loss, and pre-eclampsia-like symptoms. The aim of this study was to investigate the plasma proteomic/cytokine profile of pregnant BN rats in comparison to that of the Lewis (LEW) rat strain.

METHOD OF STUDY

Plasma proteomics differences were studied at day 13 of pregnancy in pooled plasma samples by differential in-gel electrophoresis, and protein identification was performed by mass spectrometry. Key protein findings and predicted cytokine differences were validated by ELISA using plasma from rats at various pregnancy stages. Proteomics data were used for ingenuity pathway analysis (IPA).

RESULTS

In-gel analysis revealed 74 proteins with differential expression between BN and LEW pregnant dams. ELISA studies confirmed increased maternal plasma levels of complement 4, prothrombin, and C-reactive protein in BN compared to LEW pregnancies. LEW pregnancies showed higher maternal plasma levels of transthyretin and haptoglobin than BN pregnancies. Ingenuity pathway analysis revealed that BN pregnancies are characterized by activation of pro-coagulant, reactive oxygen species, and immune-mediated chronic inflammation pathways, and suggested increased interleukin 6 and decreased transforming growth factor-β1 as potential upstream events. Plasma cytokine analysis revealed that pregnant BN dams have a switch from anti- to pro-inflammatory cytokines with the opposite switch observed in pregnant LEW dams.

CONCLUSION

Brown Norway rats show a maternal pro-inflammatory response to pregnancy that likely contributes to the reproductive outcomes observed in this rat strain.

Abnormal expression and clinical significance of 25-hydroxyvitamin D and sFlt-1 in patients with preeclampsia

Objective

To determine the association between levels of serum 25-hydroxyvitamin D (25[OH]D) and soluble fms-like tyrosine kinase 1 (sFlt-1) in patients with preeclampsia.

Methods

Clinical and demographic data were collected from patients with preeclampsia and healthy pregnant controls. Serum 25(OH)D and sFlt-1 levels were evaluated by enzyme-linked immunosorbent assay and their correlations were determined using Spearman’s rank correlation coefficient. Associations between serum 25(OH)D and sFlt-1 levels and disease severity and clinical parameters were evaluated.

Results

Significantly lower serum 25(OH)D and higher sFlt-1 levels were observed in patients with preeclampsia (n = 100) versus controls (n = 100), and 25(OH)D was inversely correlated with sFlt-1 in patients with preeclampsia. Serum 25(OH)D levels were reduced, while sFlt-1 concentration was increased in patients with severe versus mild preeclampsia. Serum 25(OH)D levels were reduced in late-onset versus early-onset severe preeclampsia. Patients with preeclampsia who had lower serum 25(OH)D or elevated sFlt-1 levels showed significantly higher blood pressure indexes versus those with higher 25(OH)D or lower sFlt-1.

Conclusions

Low serum 25(OH)D and high sFlt-1 may be candidate biomarkers for preeclampsia diagnosis and prognosis.

Vitamin D supplementation and incident preeclampsia: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Maternal vitamin D deficiency has been associated with an increased risk for preeclampsia. Despite this, the current evidence regarding the efficacy of vitamin D supplementation in preventing preeclampsia is controversial. To assess the impact of vitamin D supplementation on the risk of preeclampsia, we performed a systematic review of the literature and a meta-analysis of the available randomized clinical trials (RCTs).

METHODS

The primary outcome was preeclampsia. Subgroup analyses were carried out considering the timing of the supplementation, type of intervention and the study design. Meta-regression analysis, including the amount of vitamin D and maternal age, were planned to explore heterogeneity (PROSPERO database registration number: CRD42019119207).

RESULTS

Data were pooled from 27 RCTs comprising 59 arms, which included overall 4777 participants, of whom 2487 were in the vitamin D-treated arm and 2290 in the control arm. Vitamin D administration in pregnancy was associated with a reduced risk of preeclampsia (odd ratio [OR] 0.37, 95% confidence interval [CI]: 0.26, 0.52; I² = 0%). If the vitamin D supplementation was started up to 20 weeks' gestation, the odds was a little lower (OR 0.35, 95% CI: 0.24, 0.50, p < 0.001). The effect was largely independent of the supplementation cessation (until delivery or not), type of intervention (vitamin D alone or in association with calcium), and study design. Increasing dose of vitamin D was associated with reduced incidence of preeclampsia (slope of log OR: -1.1, 95% CI: -1.73, -0.46; p < 0.001).

CONCLUSIONS

Results suggest that vitamin D supplementation may be useful in preventing preeclampsia. These data are especially useful for health-care providers who engage in the management of pregnant women at risk for preeclampsia. Our findings are a call for action to definitively address vitamin D supplementation as a possible intervention strategy in preventing preeclampsia in pregnancy.

Evidence of an Association Between Vitamin D Deficiency and Preterm Birth and Preeclampsia: A Critical Review

Vitamin D deficiency has been associated with adverse pregnancy and birth outcomes such as increased risk for preterm birth and preeclampsia. This state of the science review analyzed recently published meta-analyses and relevant studies that have evaluated the association between vitamin D deficiency and preeclampsia or preterm birth. The results suggest that a positive association between vitamin D deficiency and preterm birth exists. However, the findings of the relationship between vitamin D deficiency and preeclampsia were inconclusive, possibly because of the need for supplementation to occur prior to placentation. This may be because of a lack of studies with ethnic minority populations, who are more likely to experience vitamin D deficiency, and inadequate supplementation doses used for treatment of vitamin D deficiency. Health care providers should screen pregnant women at risk for vitamin D deficiency and supplement women accordingly based on their vitamin D status. Lastly, well-designed and standardized clinical trials need to include large cohorts of minority pregnant women to establish the impact of vitamin D supplementation on improving preterm birth and preeclampsia risk in pregnancy.

Evidence-Based Prevention of Preeclampsia: Commonly Asked Questions in Clinical Practice

In this review, we discuss the recent literature regarding the prevention of preeclampsia and aim to answer common questions that arise in the routine antenatal care of pregnant women. Prescription of low-dose aspirin for high-risk patients has been shown to reduce the risk of preeclampsia (PE). A daily dose between 100 and 150 mg taken in the evening should be initiated prior to 16 weeks of gestation and can be continued until delivery. Calcium supplementation seems to be advantageous but currently it is only considered for patients with poor dietary intake and high risk for PE. Recent data about heparin are still conflicting, and therefore, heparin can currently not be recommended in the prevention of PE.

Vitamin D and the skin: what should a dermatologist know?

Although first discovered in 1931, vitamin D has seen an increased interest in the scientific community over the past decades, including the dermatology field. Vitamin D promotes calcium and phosphorus absorption; however, the actions of vitamin D are not confined to bone. Indeed, there is now overwhelming and compelling scientific data that vitamin D plays a crucial role in a plethora of cellular function and in extra-skeletal health. Except for fatty fish livers, very few foods naturally contain vitamin D; and the major source of vitamin D comes from skin exposure to sunlight via ultraviolet B. Keratinocytes are unique in the body as not only do they provide the primary source of vitamin D for the body, but they also possess both the enzymatic machinery to metabolize the vitamin D produced to active metabolites. This has been referred to as the photoendocrine vitamin D system. Vitamin D regulates keratinocytes proliferation and differentiation; and plays a role in the defense against opportunistic infections. Multiple factors are linked to vitamin D status; and a growing number of dermatologic diseases has been linked to vitamin D status such as atopic dermatitis, psoriasis, vitiligo, and cutaneous cancers. In this article, we reviewed the potential determinants of vitamin D status, as its implications in dermatologic diseases.

The association between calcium supplement and preeclampsia and gestational hypertension: a systematic review and meta-analysis of randomized trials

OBJECTIVES

The purpose of this study is to investigate whether calcium supplement with or without other drugs could reduce the risk of preeclampsia and gestational hypertension based on existed evidence, and to clarify whether there is discrepant effect among different population and using different dose.

METHODS

PubMed, Cochrane library, and EMBASE database were searched. Two authors independently screened all records and extracted data. The meta-analysis was performed to calculate risk ratios and 95% CIs using random-effects models.

RESULTS

27 studies, with 28 492 pregnant women were included. The results showed calcium supplement was associated with lower incidence of preeclampsia (RR 0.51, 95% CI: 0.40 to 0.64) and gestational hypertension (RR 0.70, 95% CI: 0.60 to 0.82). Sub-analyses revealed high-dose (1.2-2 g/day), moderate-dose (0.6-1.2 g/day), and low-dose (<0.6 g/day) of calcium supplement could reduce the risk of preeclampsia. For gestational hypertension, only high dose and moderate dose groups were associated with reducing the risk of gestational hypertension. However, we could draw a conclusion which does group was the most protective, as we were unable to directly compare the effects of different doses.

CONCLUSIONS

This study indicated calcium supplementation might decrease the risk of preeclampsia and gestational hypertension. And results of subgroups analyses enhanced our confidence to the protective effect of calcium supplementation. However, further studies with direct comparison of different dose of calcium supplementation are needed to explore the ideal dose of calcium supplementation to prevent preeclampsia and gestational hypertension.

Dietary patterns before and during pregnancy and maternal outcomes: a systematic review

BACKGROUND

Hypertensive disorders of pregnancy (HDP) and gestational diabetes mellitus (GDM) are common maternal complications during pregnancy, with short- and long-term sequelae for both mothers and children.

OBJECTIVE

Two systematic review questions were used to examine the relation between 1) dietary patterns before and during pregnancy, 2) HDP, and 3) GDM.

METHODS

A search was conducted from January 1980 to January 2017 in 9 databases including PubMed, Embase, and Cochrane. Two analysts independently screened articles using a priori inclusion and exclusion criteria; data were extracted from included articles, and risk of bias was assessed. After qualitative synthesis, a conclusion statement was drafted for each question and the evidence supporting the conclusion was graded.

RESULTS

Of the 9103 studies identified, 8 [representing 4 cohorts and 1 randomized controlled trial (RCT)] were included for HDP and 11 (representing 6 cohorts and 1 RCT) for GDM. Limited evidence in healthy Caucasian women with access to health care suggests dietary patterns before and during pregnancy that are higher in vegetables, fruits, whole grains, nuts, legumes, fish, and vegetable oils and lower in meat and refined grains are associated with reduced risk of HDP, including preeclampsia and gestational hypertension. Limited but consistent evidence suggests certain dietary patterns before pregnancy are associated with reduced risk of GDM. These protective dietary patterns are higher in vegetables, fruits, whole grains, nuts, legumes, and fish and lower in red and processed meats. Most of the research was conducted in healthy, Caucasian women with access to health care. Insufficient evidence exists on the associations between dietary patterns before and during pregnancy and risk of HDP in minority women and those of lower socioeconomic status, and dietary patterns during pregnancy and risk of GDM.

CONCLUSIONS

Although some conclusions were drawn from these systematic reviews, more research is needed to address gaps and limitations in the evidence.

Micronutrient supplementation in pregnancy: Who, what and how much?

Pregnancy represents a period of major physiological and metabolic change, aiming to ensure proper fetal growth and development, as well as maternal preservation. This review focuses on maternal nutrition, and particularly on micronutrient deficiencies and supplementation during pregnancy. Nutrient deficiencies and consequences in pregnant women are presented, with an overview of current recommendations for dietary supplementation in pregnancy, even considering the risk of micronutrient overload. Appropriate universal supplementation and prophylaxis/treatment of nutritional needs currently appear to be the most cost-effective goal in low-income countries, thus ensuring adequate intake of key elements including folate, iron, calcium, vitamin D and A. In high-income countries, a proper nutritional assessment and counselling should be mandatory in obstetric care in order to normalize pregestational body mass index, choose a healthy dietary pattern and evaluate the risk of deficiencies.

Uses of dietary supplements and herbal medicines during pregnancy in women undergoing assisted reproductive technologies- A study of taiwan birth cohort

OBJECTIVE

This study aimed to assess the efficacy of dietary supplements and herbal medicines for the care of pregnant women undergoing assisted reproductive technologies (ART).

MATERIALS AND METHODS

A total of 366 women undergoing ART and their children from the dataset of Taiwan Birth Cohort Study (TBCS, 2005) were enrolled in this study. Structured questionnaires were applied to collect the health information at 6-month follow-up after their delivery. The related use patterns were analyzed to investigate the final birth outcomes.

RESULTS

Comparing with those of non-ART group, the women undergoing ART consumed more supplements of multivitamin, fish oil, and calcium than herbal medicines during pregnancy. This study revealed that the consumptions of multivitamin, calcium pills, Genseng, and Suz-Wu-Tang were associated with low birth weight, whereas the intake of Huanglian was associated with birth weight. Besides, the uses of multivitamin and Suz-Wu-Tang were related to lower gestational age of infants.

CONCLUSIONS

Physicians and nurses must educate themselves in dietary supplements and herbal/alternative medicines for offering accurate advices for pregnant women to optimize their care. The results could be of reference for further investigation on longitudinal effects of dietary supplements and herbal medicines during pregnancy in women undergoing ART continuously followed with TBCS.

The Role of Vitamin D in Fertility and during Pregnancy and Lactation: A Review of Clinical Data

Vitamin D deficiency is common and there exists a huge gap between recommended dietary vitamin D intakes and the poor vitamin D supply in the general population. While vitamin D is important for musculoskeletal health, there are accumulating data suggesting that vitamin D may also be important for fertility, pregnancy outcomes and lactation. Significant changes in vitamin D metabolism during pregnancy such as increased production of the “active vitamin D hormone” calcitriol support the important role of vitamin D in this setting. Observational studies show that vitamin D deficiency is a risk marker for reduced fertility and various adverse pregnancy outcomes and is associated with a low vitamin D content of breast milk. Meta-analyses of randomized controlled trials (RCTs) document that physiological vitamin D supplementation during pregnancy is safe and improves vitamin D and calcium status, thereby protecting skeletal health. Although certain RCTs and/or meta-analyses reported some other beneficial effects, it is still not clear whether vitamin D supplementation improves fertility or decreases the risk of adverse pregnancy outcomes such as low birth weight, pre-eclampsia and neonatal mortality, or reduces wheeze/asthma in the infants. Nevertheless, vitamin D supplementation in pregnant women is frequently required to achieve a sufficient vitamin D status as recommended by nutritional vitamin D guidelines. In this review, we provide an overview of systematic reviews, meta-analyses and large trials reporting clinical data on the role of vitamin D for fertility, pregnancy and lactation.

The Association of Vitamin D Levels with Common Pregnancy Complications

The association between vitamin D deficiency and various adverse pregnancy outcomes has been extensively investigated in recent years. The pregnant woman is the only source of vitamin D for the foetus. The main sources of vitamin D for pregnant women are sunlight, fortified dairy products, oily fish and dietary supplements. Vitamin D deficiency during pregnancy has been associated with some adverse neonatal outcomes as well as an increased risk of late pregnancy complications. The outcomes of the published studies investigating preeclampsia and gestational diabetes mellitus vary with some large trials suggesting a potential positive effect of vitamin D supplementation during pregnancy on the decreased risk of these complications. Research also suggests a possible connection between lower vitamin D concentrations and increased risk of preterm labour. In our manuscript, we aim to review the existing literature regarding the prevalence of vitamin D deficiency during pregnancy, the factors associated with vitamin D deficiency, and possible pregnancy complications arising from it.

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

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

Seasonality of hypertensive disorders of pregnancy - A South Australian population study

OBJECTIVES

To investigate the seasonal variation of hypertensive disorders of pregnancy (HDP) in South Australia.

STUDY DESIGN

Retrospective population study including all 107,846 liveborn singletons during 2007-2014 in South Australia. Seasonality in incidence of HDP in relation to estimated date of conception (eDoC) and date of birth (DoB) were examined using Fourier series analysis.

MAIN OUTCOME MEASURES

Seasonality of HDP in relation to eDoC and DoB.

RESULTS

During 2007-2014, the incidence of HDP was 7.1% (n = 7,612). Seasonal modeling showed a strong relationship between HDP and eDoC (p < .001) and DoB (p < .001). Unadjusted and adjusted models (adjusted for maternal age, body mass index, ethnicity, parity, type of health care, smoking and gestational diabetes mellitus) demonstrated the presence of a peak incidence (7.8%, 7.9% respectively) occurring among pregnancies with eDoC in late Spring (November) and a trough (6.4% and 6.3% respectively) among pregnancies with eDoC in late Autumn (May). Both unadjusted and adjusted seasonal modelling showed a peak incidence of HDP for pregnancies with DoB in August (8.0%, 8.1% respectively) and a nadir among pregnancies with eDoB in February (6.2%).

CONCLUSION

The highest incidence of HDP was associated with pregnancies with eDoC during late spring and summer and birth in winter, while the lowest incidence of HDP was associated with pregnancies with eDoC during late autumn and early winter and birth in summer. Nutrient intake, in particular vitamin D, sunlight exposure and physical activity may affect maternal, fetal and placental adaptation to pregnancy and are potential contributors to the seasonal variation of HDP.