Association between serum vitamin D level during pregnancy and recurrent spontaneous abortion: a systematic review and meta-analysis

Effects of vitamin D in pregnancy on maternal and offspring health-related outcomes: An umbrella review of systematic review and meta-analyses

BACKGROUND

Vitamin D deficiency has been linked with several adverse maternal and fetal outcomes.

OBJECTIVE

To summarize systematic reviews and meta-analyses evaluating the effects of vitamin D deficiency and of vitamin D supplementation in pregnancy on maternal and offspring health-related outcomes.

METHODS

Prior to conducting this umbrella review, we registered the protocol in PROSPERO (CRD42022368003). We conducted searches in PubMed, Embase, and Cochrane Library for systematic reviews and meta-analyses on vitamin D in pregnancy, from database inception to October 2, 2023. All outcomes related to vitamin D in pregnancy obtained from the systematic reviews and meta-analyses were extracted.

DATA EXTRACTION

Two reviewers independently chose studies and collected information on health outcomes. The quality of the included articles' methodology was assessed using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews-2).

RESULTS

We identified 16 eligible systematic reviews and meta-analyses, which included 250,569 women. Our results demonstrated that vitamin D deficiency in pregnancy is associated with increased risk of preterm birth, small-for gestational age/low birth weight infants, recurrent miscarriage, bacterial vaginosis and gestational diabetes mellitus. Vitamin D supplementation in pregnancy increases birth weight, and reduces the risk of maternal pre-eclampsia, miscarriage, and vitamin D deficiency, fetal or neonatal mortality, as well as attention-deficit hyperactivity disorder, and autism spectrum disorder in childhood. In women with gestational diabetes mellitus, vitamin D supplementation in pregnancy can reduce the risk of maternal hyperbilirubinemia, polyhydramnios, macrosomia, fetal distress, and neonatal hospitalization.

CONCLUSION

Due to the association with adverse maternal and offspring health outcomes, we recommend the vitamin D status in pregnancy should be monitored, particularly in women at high risk of vitamin D deficiency. It is suggested that pregnant women take a dose of >400 IU/day of vitamin D supplementation during pregnancy to prevent certain adverse outcomes.

The Relationship Between the Average Decreased Times of Estradiol and Early Miscarriage: An Observational Study

Decreased estradiol (E2) levels are associated with early miscarriage (EM), but the relationship between decreased times of E2 and EM has not been reported. We aimed to investigate the relationship between the average decreased times of E2 (ADTE) and EM. Women with a history of miscarriage were retrospectively recruited from the Reproductive Center of Lanzhou University Second Hospital (Lanzhou, China) between September 2019 and February 2022. Based on pregnancy outcome, they were divided into ongoing pregnancy group (n = 359) and EM group (n = 104). In addition, subgroup analyses were performed for the number of previous miscarriages and whether E2 levels decreased continuously. The exposure and outcome variables were ADTE and miscarriage before 12 weeks of gestation, respectively. Totally, 1171 patients were recruited and 463 patients were finally analyzed. ADTE was associated with EM (odds ratio [OR] = 1.346, 95% confidence interval [CI]1.154-1.571, P < 0.001). When ADTE ≥ 2.5, the EM risk increased 1.17-fold compared to patients with 0-1.249 times (OR = 2.170, 95% CI 1.144-4.117, P = 0.018). Moreover, a threshold effect existed in the ADTE and the risk of EM with a value of 4.9 times. When exceeding 4.9 times, the EM risk increased 4.713-fold for each increased unit (OR = 5.713, 95% CI 1.255-23.170, P = 0.024). Subgroup analysis showed that ADTE had a greater effect on the occurrence of EM in women with a history of 1-2 miscarriages than in women with 3 miscarriages. Decreased E2 was a risk factor for EM regardless of whether it dropped continuously or not. In conclusion, our study identifies a potential link between ADTE and early miscarriage risk in women with prior miscarriages, yet cautious interpretation is necessary due to inherent design limitations. Further research with prospective designs and large population samples is essential to validate ADTE's utility as a predictive indicator for early miscarriage in clinical settings.

No evidence of a causal relationship between miscarriage and 25-hydroxyvitamin D: a Mendelian randomization study

STUDY QUESTION

Is there a causal relationship between 25-hydroxyvitamin D (25OHD) and miscarriage?

SUMMARY ANSWER

In this study, little evidence of a causal relationship was found between low serum 25OHD concentration or vitamin D deficiency and the risk of miscarriages.

WHAT IS KNOWN ALREADY

Associations between low vitamin D levels and increased risk of miscarriage have been reported, but causality is unclear.

STUDY DESIGN SIZE DURATION

The latest and largest genome-wide association studies (GWAS) for serum 25OHD concentration (n = 417 580), vitamin D deficiency (426 cases and 354 812 controls), miscarriage (16 906 cases and 149 622 controls), and the number of miscarriages (n = 78 700) were used to explore the causal association between serum vitamin D levels and miscarriage by two-sample Mendelian randomization analysis.

PARTICIPANTS/MATERIALS SETTING METHODS

This study was based on summary GWAS results from the FinnGen database and the UK Biobank. The random-effect inverse-variance weighted method was regarded as the primary analysis; MR-Egger, weighted median, weighted mode, simple mode, and MR-pleiotropy residual sum and outlier (MR-PRESSO) were further employed as complementary methods. MR-Egger intercept analysis and MR-PRESSO were employed to test pleiotropy, and Cochran's Q statistic and leave-one-out sensitivity analysis were used to determine the heterogeneity and robustness of the overall estimates, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

There was insufficient evidence of causal associations between serum 25OHD concentration and miscarriage (odds ratio (OR) = 0.995, 95% CI: 0.888 to 1.114, P = 0.927), or the number of miscarriages (β = -0.004, 95% CI: -0.040 to 0.032, P = 0.829). Furthermore, little evidence of causality between genetically determined vitamin D deficiency to miscarriage (OR = 0.993, 95% CI: 0.966 to 1.021, P = 0.624), or the number of miscarriages (β = 0.001, 95% CI: -0.009 to 0.011, P = 0.828), was observed. The results of the sensitivity analysis were robust, and no significant heterogeneity or horizontal pleiotropy was found.

LIMITATIONS REASONS FOR CAUTION

This study is limited by the absence of female-specific GWAS data and the limited amount of GWAS data available for this study, as well as the need for caution in generalizing the findings to non-European ethnic groups.

WIDER IMPLICATIONS OF THE FINDINGS

These findings enhance the current understanding of the intricate association between vitamin D and pregnancy outcomes, challenging prevailing beliefs regarding the strong association with miscarriage. The results provide a special perspective that may prompt further exploration and potentially offer insights for guiding future research and informing clinical guidelines pertaining to the management of miscarriage.

STUDY FUNDING/COMPETING INTERESTS

This project was supported by the Hubei Provincial Natural Science Foundation Program General Surface Project (2022CFB200), the Key Research & Developmental Program of of Hubei Province (2022BCA042), the Fundamental Research Funds for the Central Universities (2042022gf0007, 2042022kf1210), and the Interdisciplinary Innovative Talents Foundation from Renmin Hospital of Wuhan University (JCRCWL-2022-001, JCRCYG-2022-009). All authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Study on the clinical value of Vitamin D in recurrent spontaneous abortion: Revisiting the Importance of Vitamin D

OBJECTIVE

This study explores the possible pathogenesis of recurrent spontaneous abortion (RSA) caused by vitamin D (VD), provides evidence-based bases for prevention and treatment of RSA, improves female reproductive health.

METHODS

This study randomly selected 305 patients without spontaneous abortion (SA0), 216 patients with a spontaneous abortion (SA1) and 200 patients with RSA from 1421 women of childbearing age who visited the RSA specialty clinic of Hangzhou First People's Hospital from January 2021 to June 2023 to conduct a prospective clinical study. Then, we collected the data of clinical diagnosis and treatment, conducted intervention and follow-up, and finally executed statistical analysis.

RESULTS

(1) RSA patients were significantly older than the other two groups. (2) The rates of VD deficiency in SA1 and RSA patients were significantly higher than those in SA0. (3) When BMI < 20  or > 24 kg/m2 , there were abnormal increase in VD and increased number of spontaneous abortions. (4) The bilateral S/D of the VD-sufficient, VD-insufficient and VD-deficient groups gradually increased with statistical significance (p ≤ .018). (5) Among the 65 cases undergoing embryo chromosome examinations, chromosomal abnormalities accounted for 55.38% and 69.05% in RSA patients. (6) Among 186 patients with abnormal ACA, there was a certain negative correlation between ACA and VD, which was stronger among RSA patients. Moreover, ACA significantly decreased (p < .001) after effectively supplementing VD, and the miscarriage rate of re-pregnancy also decreased.

CONCLUSION

The rate of VD deficiency is higher in RSA patients. VD deficiency may be related to the age of women of childbearing age and too low or high BMI, and may cause abnormal plasma antiphospholipid antibodies, increased uterine artery resistance and abnormal chromosomal division during fertilization, leading to spontaneous abortion and even RSA. The improvement of VD deficiency may reduce the risk of RSA occurrence.

Calcifediol in the management of vitamin D deficiency-related skeletal and extraskeletal diseases: overview and clinical cases

As well as being essential for musculoskeletal health, vitamin D is involved in numerous other physiological processes. Poor vitamin D status is linked to a wide range of diseases, including cardiovascular disease, autoimmune conditions, pulmonary disorders and upper respiratory tract infections. While optimal target concentrations of serum 25-hydroxyvitamin D (25(OH)D) for health maintenance or therapeutic purposes are still the subject of debate, there is reasonable agreement that serum 25(OH)D levels <50 nmol/L (20 ng/mL) constitute vitamin D deficiency and that severe deficiency states (serum 25(OH)D levels <25-30 nmol/L ≈ 10-12 ng/mL) should be avoided. Main strategies to maintain or improve vitamin D status are food supplementation and therapeutic use of medicinal forms of vitamin D. In this review, we examine evidence that implicates vitamin D deficiency in diverse conditions in the clinical settings of endocrinology, rheumatology, pneumology and reproductive health. Cholecalciferol (vitamin D3) is the most frequently used vitamin D supplement worldwide, though calcifediol (25-hydroxyvitamin D3) has recently become more widely available. Calcifediol is one step closer than cholecalciferol in the metabolic pathway to biologically active vitamin D. Pharmacokinetic differences between these vitamin D metabolites confer putative advantages for calcifediol in certain clinical situations. The clinical use of calcifediol is explored more closely through case studies, which illustrate its adjunctive role in the treatment of several vitamin D deficiency-related skeletal and extraskeletal diseases.