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

Impact of particulate-matter air pollution on 25-hydroxyvitamin D levels: a mendelian randomisation study

OBJECTIVES

In observational studies, the 25-hydroxyvitamin D (25(OH)D) level in body has been found to be closely related to particulate matter (PM) air pollution. In this study, we used the two-sample mendelian randomisation (MR) method to investigate and discuss the potential causal relationship and mode of influence.

STUDY DESIGN

MR study.

METHODS

PM data (PM10, PM2.5-10, PM2.5, PM2.5 absorbance) came from the UK Biobank database, and 25(OH)D data came from European Bioinformatics Institute (EBI) database. The analysis was conducted utilising three prominent methods (inverse-variance-weighted [IVW], MR-Egger, weighted median, weighted mode, and simple mode). The primary emphasis was placed on IVW, accompanied by heterogeneity and horizontal pleiotropy tests. Furthermore, sensitivity analysis was undertaken.

RESULTS

The MR analysis revealed a significant association between exposure to PM10 and a decrease in levels of 25(OH)D (odds ratio [OR]: 0.878, 95% confidence interval [CI]: 0.789-0.977). However, no significant relationship was observed between PM2.5 exposure and 25(OH)D (OR: 0.943, 95%CI: 0.858-1.037). Further analysis indicated that the main contributor to the decline in 25(OH)D levels is linked to PM2.5-10 exposure (OR: 0.840, 95%CI: 0.751-0.940) and PM2.5 absorbance (OR: 0.875, 95%CI: 0.824-0.929). No heterogeneity and horizontal pleiotropy existed.

CONCLUSIONS

The MR results suggest that PM (PM10, PM2.5-10 and PM2.5 absorbance) exposure lowers vitamin D (VD) levels, but PM2.5 was not found to have a significant effect on VD in humans.

Vitamin D and its role in gynecology: emerging importance of checking vitamin D status in certain gynecological entities

Among non-bone effects of vitamin D, the three main chronological stages in gynecology ‒ menarche, reproductive stage and menopause/postmenopause - are possibly impacted by vitamin D deficiency. A large amount of emerging data show that vitamin D is a confounding factor in these parameters. Gynecology stays at the crossroads with endocrinology and, in the light of the rising knowledge about the involvement of vitamin D in many gynecological disorders, it is worth to investigate the exact role of vitamin D in this area. Especially since vitamin D is easy to substitute in case of deficiency. Authors present some emerging data on the role of vitamin D in gynecology, suggesting when it is necessary to check vitamin D status to intervene with vitamin D supplementation and raising gynecologists' awareness of the need for further clinical studies.

The impact of vitamin D changes during pregnancy on the development of maternal adverse events: a random forest analysis

BACKGROUND

Maternal vitamin D deficiency during pregnancy has been associated with various maternal adverse events (MAE). However, the evidence regarding the effect of vitamin D supplementation on these outcomes is still inconclusive.

METHODS

This secondary analysis utilized a case-control design. 403 samples with MAE and 403 samples without any outcomes were selected from the Khuzestan Vitamin D Deficiency Screening Program in Pregnancy study. Random forest (RF) analysis was used to evaluate the effect of maternal vitamin D changes during pregnancy on MAE.

RESULTS

The results showed that women who remained deficient (35.2%) or who worsened from sufficient to deficient (30.0%) had more MAE than women who improved (16.4%) or stayed sufficient (11.8%). The RF model had an AUC of 0.74, sensitivity of 72.6%, and specificity of 69%, which indicate a moderate to high performance for predicting MAE. The ranked variables revealed that systolic blood pressure is the most important variable for MAE, followed by diastolic blood pressure and vitamin D changes during pregnancy.

CONCLUSION

This study provides evidence that maternal vitamin D changes during pregnancy have a significant impact on MAE. Our findings suggest that monitoring and treatment of vitamin D deficiency during pregnancy may be a potential preventive strategy for reducing the risk of MAE. The presented RF model had a moderate to high performance for predicting MAE.

Clinical practice of vitamin D screening and supplementation in pregnancy in Asia-pacific countries: A cross-sectional study

Background

Vitamin D deficiency is common in pregnant women. There is scarce information in the Asia-Pacific region on the understanding of vitamin D screening and supplementation in pregnancy among health care professionals.

Methods

We performed a cross-sectional study among health care professionals who are part of the Integrated Platform for Research in Advancing Metabolic Health outcomes of Women and Children (IPRMAHO) international study group on their understanding and perception of Vitamin D screening and supplementation in pregnancy. The cross-sectional survey comprised 4 main sections: demographics, existing policies, nutrient supplementation in pregnancy and various practices on screening, treatment and perceptions, with a total of 22 questions. A total of 15 responses were obtained from attendees from distinct health facilities across eleven participating Asia-Pacific countries.

Results

Majority of the surveyed hospitals (11/15, 78.6 %) did not have a national policy or regional guideline regarding Vitamin D screening and supplementation in pregnancy. More than half of respondents were (9/14, 64.3 %) were unsure of the percentage of women seen with Vitamin D deficiencies each year and were unsure of Vitamin D dosage prescribed to pregnant women with (8/15, 53.3 %) or without (6/14, 42.9 %) Vitamin D deficiency. Vitamin D was rarely prescribed in pregnancy when compared to other nutrient supplements such as folic acid and iron. Majority of respondents (9/11, 72.7 %) indicated that their hospital did not screen for Vitamin D deficiencies in pregnancy, even amongst high risk pregnant women. Nevertheless, majority of respondents indicated a need (12/15, 80.0 %) for a guideline or consensus regarding Vitamin D screening and supplementation in pregnancy.

Conclusion

While majority of the surveyed hospitals did not have a national policy or regional guideline regarding Vitamin D screening and supplementation in pregnancy, majority of respondents indicated a need for the policy or guideline. There were varying clinical knowledge gaps and different perceptions on Vitamin D screening and supplementation in pregnancy among healthcare professionals.

Vitamin D Status as an Important Predictor of Preterm Birth in a Cohort of Black Women

Vitamin D deficiency (25 (OH)D < 20 ng/mL) is a modifiable risk factor that has been associated with an increased risk of preterm birth (PTB) (<37 weeks gestation). Black women are at a high risk for vitamin D deficiency due to higher melanin levels. Vitamin D sufficiency may be protective against PTB risk in Black women. Black participants between 8 and 25 weeks of gestation were included in this nested case-control study. The sample consisted of women who had either PTBs (n = 57) or term births, were selected based on maternal age compared to those who had PTBs (n = 118), and had blood samples available between 8 and 25 weeks of gestation. The women completed questionnaires about depressive symptoms and smoking behavior and had blood collected to determine their vitamin D levels. Gestational age at birth, hypertensive disorders, and body mass index (BMI) were collected from the medical records. The odds of PTB were increased by 3.34 times for participants with vitamin D deficiency after adjusting for hypertensive disorders of pregnancy and depressive symptoms. Vitamin D assessment and supplementation may be an important intervention for preventing PTB in pregnant Black women.

Stress of Prematurity in the Experience of the COVID-19 Pandemic-Current State of Knowledge

Stress is a process that triggers various physiological, hormonal and psychological mechanisms in response to a threat, which significantly affects the health of an individual. The COVID-19 pandemic introduced a lot of social changes that required constant adaptation to unfavorable conditions. The aim of the study was to assess the impact of stress related to this pandemic on pregnant women, mothers of premature infants and their families, and on obstetric complications, particularly preterm birth. A comprehensive literature review was performed using electronic databases such as Pubmed, Science Direct and Google Scholar. Keywords such as: "prematurity"; "pregnancy"; "stress"; "COVID-19" and various combinations of the above were used. Maternal stress and anxiety increase the levels of corticotropin-releasing hormone (CRH) in the placenta, which in turn affects the incidence of preterm birth and many other related maternal and neonatal complications. In addition, it was found that SARS-CoV-2 infection may increase the risk of this phenomenon. The COVID-19 pandemic has adversely affected preterm birth rates and the mental health of mothers of preterm infants, exacerbating their negative experience of having a premature baby. More research is needed to demonstrate the long-term effects of COVID-19 stress on prematurity.

Trimester-specific associations of maternal dietary patterns with preterm birth: China Medical University birth cohort study

The trimester-specific associations of maternal dietary patterns with preterm birth (PTB) are unclear. In a prospective prebirth cohort study, we aimed to examine the critical time window of maternal prenatal dietary patterns and the risk of PTB. We assessed prenatal dietary intake among 1500 pregnant women with validated food frequency questionnaires during the 1st, 2nd and 3rd trimester, respectively. We used logistic regression models and generalized estimating equation models to examine the trimester-specific associations and longitudinal associations between maternal dietary patterns in relation to risk of PTB and PTB subtypes. The incidence rate of PTB was 11.9% (179 out of 1500 pregnant women) in the present study. We observed that maternal adherence to a fish-seafood pattern in the 1st trimester was associated with higher risk of PTB [tertile 3 (T3) vs. tertile 1 (T1): OR = 2.29, 95% CI: 1.32-3.96] and iatrogenic preterm birth (IPTB) (T3 vs. T1: OR = 2.26, 95% CI: 1.21-4.20), while a fish-seafood pattern in the 2nd trimester was associated with lower risk of PTB (T3 vs. T1: OR = 0.49, 95% CI: 0.25-0.93). Maternal adherence to a dairy-egg pattern in the 2nd or 3rd trimester was associated with higher risks of PTB and IPTB. No dietary patterns were associated with spontaneous preterm birth. Our findings provide new evidence that specific dietary patterns during different trimesters may have different and even inverse health effects on pregnant women. This supports the necessity of guiding the maternal diet according to different periods of pregnancy to prevent PTB.

Association between season of conception, month of conception with preterm birth in China: a population-based retrospective cohort study

BACKGROUND

Seasonal patterns of preterm birth were identified in previous studies, but the effect of conception season on preterm birth has not been extensively studied. Based on the notion that the etiological roots of preterm birth lie in the beginning of pregnancy, we did a population-based retrospective cohort study in Southwest China to examine the effects of season of conception and month of conception on preterm birth.

METHODS

We did a population-based retrospective cohort study in women (aged 18-49) who participated in the NFPHEP from 2010 to 2018, and had a singleton livebirth in southwest China. According to the time of the last menstruation reported by the participants, month of conception and season of conception were then ascertained. We used multivariate log-binomial model to adjust the potential risk factors for preterm birth and obtained adjusted risk ratio (aRR) and 95% confidence intervals (95%CI) for conception season, conception month and preterm birth.

RESULTS

Among 194 028 participants, 15 034 women had preterm birth. Compared with pregnancies that were conceived in the summer, pregnancies that were conceived in the spring, autumn and winter had the higher risk of preterm birth (Spring: aRR = 1.10, 95% CI: 1.04-1.15; Autumn: aRR = 1.14, 95% CI: 1.09-1.20; Winter: aRR = 1.28, 95% CI: 1.22-1.34) and also had a higher risk of early preterm birth (Spring: aRR = 1.09, 95% CI: 1.01-1.18; Autumn: aRR = 1.09, 95% CI: 1.01-1.19; Winter: aRR = 1.16, 95% CI: 1.08-1.25). Pregnancies in December, and January had a higher risk of preterm birth and early preterm birth than pregnancies that were conceived in July.

CONCLUSIONS

Our study found that preterm birth was significantly related to season of conception. Preterm and early preterm birth rates were the highest among pregnancies that were conceived in winter, and the lowest among pregnancies in summer.

Correlation between meteorological factors and vitamin D status under different season

Pregnant women with low vitamin D levels tend to have poor clinical outcomes. Meteorological factors were associated with vitamin D. Here, we aimed to study the current status of 25-Hydroxy vitamin D (25(OH)D) concentrations in pregnant women in Kunshan city and investigate the meteorological factors associated with 25(OH)D levels under different seasons. The correlation between meteorological factors and 25(OH)D levels was estimated by cross-correlation analysis and multivariate logistic regression. A restrictive cubic spline method was used to estimate the non-linear relationship. From 2015 to 2020, a total of 22,090 pregnant women were enrolled in this study. Pregnant women with 25(OH)D concentrations below 50 nmol/l represent 65.85% of the total study population. There is a positive correlation between temperature and 25(OH)D. And there is a protective effect of the higher temperature on vitamin D deficiency. However, in the subgroup analysis, we found that in autumn, high temperatures above 30 °C may lead to a decrease in 25(OH)D levels. This study shows that vitamin D deficiency in pregnant women may widespread in eastern China. There is a potential inverted U-shaped relationship between temperature and 25(OH)D levels, which has implications for understanding of vitamin D changes under different seasons.

Maternal serum vitamin D level in early pregnancy and risk for preeclampsia: A case-control study in Southern Sweden

BACKGROUND

Preeclampsia is considered a major cause of maternal and fetal morbidity and mortality. The aim of the present case-control study in Sweden was to assess the hypothesized association between low serum vitamin D concentrations in early pregnancy and the risk of developing preeclampsia since vitamin D may play a role in early placental development.

METHODS

The study included 296 women diagnosed with preeclampsia (cases) and 580 healthy pregnant women (controls). Serum samples were obtained from a biobank of samples collected in early pregnancy including almost all pregnancies in Southern Sweden. Concentrations of 25-hydroxyvitamin D3 (vitamin D) were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The cases were divided into two categories: i) infants were born before gestational week 34 (early onset) and/or born small-for-gestational age (SGA)(n = 51), ii) and others defined as late onset (n = 245). Vitamin D concentrations were analyzed both as a continuous and a categorized variable.

RESULTS

When all preeclampsia cases were included in the analyses no consistent patterns were observed. However, the median serum concentrations of vitamin D were significantly lower among the cases who were early onset and/or were born SGA (median 39.2 nmol/L, range 1.2-93.6) as compared to the controls (49.0 nmol/L, 0.1-219; p = 0.01). In addition, high concentrations were statistically significantly associated with a decreased risk of preeclampsia (>66.9 vs ≤30.1 nmol/L; crude OR 0.39, 95% CI 0.16-0.96). When potential confounders were included in the models the associations were even more pronounced.

CONCLUSIONS

Our results support the hypothesis that vitamin D deficiency is a risk factor for preeclampsia, but only in preeclampsia cases who were early-onset and/or were born SGA. Preeclampsia is not a homogenous condition and more studies are needed before vitamin D supplementation during pregnancy can be recommended.

Serum vitamin D levels and COVID-19 during pregnancy: A systematic review and meta-analysis

Background

Serum vitamin D levels are reported to be associated with the risk of incidence and severity of COVID-19 in the general population. During pregnancy, immune system alterations in line with changes in vitamin D metabolism may affect the course of COVID-19. Thus, we aimed to systematically review the association between vitamin D, pregnancy, and COVID-19.

Methods

A systematic literature search was conducted in PubMed, Scopus, Web of Science, Embase, and Google Scholar until the end of May 2022. Mean differences (MD) with 95% CI were used as desired effect sizes to assess the association of serum vitamin D levels with the risk of incidence and severity of COVID-19 in pregnant women.

Results

Among 259 records, 7 and 6 studies were included in the systematic review and meta-analysis, respectively. All included studies had acceptable quality. Our results demonstrated an insignificant difference between infected women and non-infected controls (MD = -2.55 ng/ml, 95% CI: −6.85 – 1.74). But serum vitamin D levels in severe/moderate cases compared to mild ones (MD = −2.71 ng/ml, 95% CI: −4.18 to −1.24) are significantly lower.

Conclusion

Based on the current evidence, serum vitamin D level does not associate with the risk of SARS-CoV-2 infection among pregnant women, but we find a significant association with the severity of the disease. These findings may be helpful in similar conditions and future studies to better understand the complex immune alterations during pregnancy.

Vitamin D Deficiency During the First Trimester of Pregnancy and the Risk of Developing Gestational Diabetes Mellitus

OBJECTIVE

To investigate the relationships among various factors that affect serum vitamin D levels and vitamin D in the first trimester and the risk of developing gestational diabetes mellitus (GDM).

DESIGN

A prospective cohort design.

SETTING

The family health center of Ankara, Turkey.

PARTICIPANTS

Out of 889 pregnant women who participated in the study in the first trimester (6-13 weeks gestation), 814 participated in GDM screening in the second trimester (24-28 weeks gestation).

METHODS

We determined serum vitamin D levels, demographic data, various biochemical and anthropometric parameters, and factors that affect vitamin D synthesis of participants in the first trimester and used logistic regression analysis to analyze the effects of the associations among vitamin D deficiency and the other variables on the occurrence of GDM.

RESULTS

Vitamin D deficiency in the first trimester was present in 425 (82.5%) participants. In the second trimester, 198 participants (24.3%) were diagnosed with GDM through oral glucose tolerance test screening. We detected GDM in the second trimester in 5.7% of participants who had vitamin D deficiency in the first trimester. Even after adjustment for vitamin D intake, clothing style, and duration of exposure to the sun, the risk of GDM was significantly greater in participants who were vitamin D deficient than those who were not deficient. The risk of GDM among women with vitamin D deficiency was sustained or increased significantly after we adjusted for age, parity, prepregnancy body mass index, history of diabetes, triglyceride levels, vitamin D intake, clothing style, and length of sun exposure, OR = 10.60, p < .001, 95% confidence interval [2.82, 39.76].

CONCLUSIONS

Our results suggest that vitamin D deficiency in the first trimester may significantly increase the risk of developing GDM.

Impact of vitamin D on maternal and fetal health: A review

The role of vitamin D in improving maternal health and reducing the risk of developmental disorders in fetus has been an important domain of research since the past few years. Vitamin D, owing to its immunomodulatory, anti‐inflammatory, developmental roles, and regulating calcium homeostasis, is predicted to have a significant influence on maternal and fetal health status. Several observational studies and clinical trials, determining the impact of vitamin D on gestational diabetes, C‐section, postpartum depression, pre‐eclampsia, miscarriages, and preterm delivery, have been elaborated in this review. In addition, fetal birth defects including neurological development, reduced birth weight, respiratory infections, bone development, and altered anthropometrics have also been summarized with available evidences. Other important mechanisms related to the roles of vitamin D in the body are also explained. Furthermore, recent studies determining the effect of vitamin D at genetic level will also help in understanding and future design of research in the area of maternal and fetal health.

Maternal plasma levels of vitamin D in postterm pregnancy

This study was conducted to examine the levels of vitamin D in postterm pregnancy. The study consisted of two groups: Group 1: women with postterm pregnancy in whom labour has not started (n = 40). Group 2: pregnant women with spontaneous labour between 37 and 41 weeks of gestation (n = 40). Demographic characteristics of individuals, age, body mass index, gravida, parity, living child, number of abortions and birth characteristics were recorded. Prepartum and postpartum haemoglobin (Hb) and haematocrit (Hct) values ​​and vitamin D levels of pregnant women were measured. We found no significant differences in vitamin D levels, smoking, mode of delivery, induction of labour, methods of cervical ripening and maternal and perinatal complications between the groups (p > .05). D vitamin in the model had a statistically significant effect on prepartum Hb (p < .05). Vitamin D levels seem not to be associated with postterm pregnancy. Vitamin D had a statistically significant effect on prepartum Hb.IMPACT STATEMENTWhat is already known on this subject? The aetiology of post term pregnancy is not clearly known, factors such as foetal anencephaly, foetal sex, placental sulfatase deficiency, genetic factors, and high pre-pregnancy body mass index play a role.What do the results of this study add? Vitamin D levels seem not to be associated with postterm pregnancy. Vitamin D had a statistically significant effect on prepartum Hb.What are the implications of these findings for clinical practice and/or further research? Further studies are needed to clarify the relationship between vitamin D levels and postterm pregnancy.

Associations between Pregnancy-Related Symptoms, Serum 25(OH)D, and Physical Quality of Life in Pregnant Women

Vitamin D deficiency has been associated with pregnancy-related symptoms including fatigue, poor sleep quality, and musculoskeletal pain. Pregnant Black and Hispanic women are more likely to have vitamin D deficiency compared with pregnant non-Hispanic White women. Data are limited on the association of vitamin D deficiency with quality of life (QOL) among pregnant women. This study examined the association of serum 25(OH)D and pregnancy-related symptoms with QOL among pregnant predominantly minority women. Using a cross-sectional design, 119 pregnant Black and Hispanic women completed surveys and had blood drawn for serum 25(OH)D levels between 24–32 weeks gestation. Hierarchical regression analysis indicated that total pregnancy-related symptoms and serum 25(OH)D level were significant predictors of QOL, while controlling for covariates. Higher total pregnancy-related symptoms and lower serum 25(OH)D predicted poorer physical QOL. Screening for pregnancy-related symptoms and vitamin D levels among childbearing women might be important nursing interventions to improve physical QOL.

Association between maternal serum 25-hydroxyvitamin D concentrations and the risk of pre-eclampsia in central Sudan: a case-control study

BACKGROUND

There are few published data on the role of vitamin D concentrations during pregnancy in sub-Saharan Africa. Thus, the aim of the current study was to investigate the association between 25-hydroxyvitamin D (25[OH)]D) levels and pre-eclampsia.

METHOD

A case-control study, with 60 women in each arm, was conducted in Medani Hospital in Sudan. The cases were women with pre-eclampsia and healthy pregnant women as controls. The medical and obstetric history was obtained using a questionnaire. The serum 25(OH)D concentrations were measured using ELISA.

RESULTS

The median (IQR) of 25(OH)D concentration was significantly lower in women with pre-eclampsia than in the controls (10.0 [6.5] vs 18.3 [22.1] ng/mL). Fifty-three cases with pre-eclampsia (88%) and 36 cases in the control group (60%) had vitamin D deficiency (25(OH)D level≤20 ng/mL). Multivariate logistic regression showed that the 25(OH)D levels were negatively associated with pre-eclampsia (adjusted OR [AOR]=0.87, 95% CI 0.81 to 0.92). Vitamin D-deficient women were at a higher risk of pre-eclampsia (AOR=4.51, 95% CI 1.70 to 11.94).

CONCLUSION

Low 25(OH)D levels were reported in women with pre-eclampsia and were an independent risk factor for pre-eclampsia.

Level of adherence to vitamin D supplementation guidelines in an antenatal centre in Birmingham, UK, and its effect on biochemical and obstetrical outcomes: a single-centre cross-sectional study

OBJECTIVES

A third of pregnant women in the UK are vitamin D deficient, which may confer deleterious consequences, including an increased risk of pre-eclampsia, gestational diabetes mellitus and intrauterine growth restriction. This study aims to determine the proportion of women that met National Institute for Health and Care Excellence (NICE) standards for vitamin D supplementation in pregnancy and compare biochemical and obstetrical outcomes according to supplementation status.

DESIGN AND SETTING

This is a single-centre cross-sectional study in an antenatal centre in Birmingham, UK. Participants received a questionnaire regarding their experiences with vitamin D supplementation during their pregnancy with their general practitioner. Serum 25-hydroxyvitamin D and bone profile results were obtained during the same appointment and obstetrical outcomes were collected retrospectively once participants had delivered.

RESULTS

41.8% of participants (n=61) received written and/or verbal advice about supplementation, (NICE standards=100%). 72.6% (n=106) had one or more risk factors for vitamin D deficiency, of which 38.7% (n=41, NICE standards=100%) were asked about supplementation. Among those asked, 85.4% (n=41, NICE standards=100%) received the correct dosage. Compared with the supplementation group, the non-supplementation group had offspring that were 1.40 cm (95% CI 0.01 to 2.80, p=0.04) longer at birth; which was significant after adjusting for confounding factors. No significant differences in any biochemical parameters were observed between supplementation categories (p>0.05).

CONCLUSIONS

Adherence to NICE standards was suboptimal. This may be attributed to insufficient training for general practitioners on the importance of supplementation, causing them to underestimate the consequences of gestational vitamin D deficiency. Recommendations include implementing a mandatory screening tool to identify 'at-risk' women and providing more clinician training to ensure that supplementation during pregnancy is standard of care.

Effects of Dietary Patterns during Pregnancy on Preterm Birth: A Birth Cohort Study in Shanghai

The objective of this study was to analyse representative dietary patterns during pregnancy in Shanghai and explore the effects of dietary patterns during pregnancy on preterm birth. Data were derived from the ‘Iodine Status in Pregnancy and Offspring Health Cohort’ (ISPOHC) study. Multistage, stratified random sampling was used to select survey participants from 16 districts in Shanghai, which were divided into five sampling areas; 40–70 pregnant women were selected from each area. A total of 4361 pregnant women and their offspring were involved in the study. The male-to-female ratio of the babies was 1.04:1, and the incidence of single preterm birth was 4.2%. Three dietary patterns were extracted by factor analysis: a ‘Vegetarian Pattern’, an ‘Animal Food Pattern’ (AFP), and a ‘Dairy and Egg Pattern’. These patterns explained 40.513% of the variance in dietary intake. Binary logistic regression, which was used to analyse the association between birth outcomes and scores measuring maternal dietary patterns, found only the AFP was a significant risk factor for preterm birth. Higher AFP scores were positively associated with preterm birth (Q2 vs. Q1 OR = 1.487, 95% CI: 1.002–2.207; Q3 vs. Q1 OR = 1.885, 95% CI: 1.291–2.754). After adjusting for other potential contributors, a higher AFP score was still a significant risk factor for preterm birth (Q2 vs. Q1 OR = 1.470, 95% CI: 0.990–2.183; Q3 vs. Q1 OR = 1.899, 95% CI: 1.299–2.776). The incidence of preterm birth was 4.2%. A higher score of AFP was significantly associated with a higher risk of preterm birth. The animal food intake of pregnant women should be reasonably consumed during pregnancy.

Features of the 1st trimester of pregnancy course with severe deficiency of 25(OH)D

INTRODUCTION

The course of physiological pregnancy is provided by many complementary factors. Thus, a deficiency in one of the links of the metabolic network contributes to the development of an imbalance in the work of the whole organism, which ensures the growth and development of the embryo from the first days of gestation. It has been demonstrated that vitamin D can act as an immune regulator during implantation, providing a protective effect in the entire period of pregnancy.

OBJECTIVE

The aim of this study is to assess the features of the course of pregnancy in patients with different levels of vitamin D in the blood in the first trimester.

MATERIALS AND METHODS

A prospective multicenter randomized study was conducted in the North-West region of the Russian Federation among 88 pregnant women in the first trimester of gestation (up to 13 weeks). All patients were divided into 3 groups depending on the initial level of vitamin D (group 1-14 women with a 25(OH)D < 10 ng/ml, group 2-62 pregnant women from 10 to 30 ng/ml, group 3-12 pregnant women with a vitamin D content >30 ng/ml).

INTERVENTIONS

Criteria of inclusion: pregnant women from 20 to 44 years of the first trimester of gestation (up to 13 weeks) with the studied level of vitamin D in the blood serum; singleton pregnancy; BMI ≤30 kg/m2; signing by the patient of informed consent for inclusion in the study group.

MAIN OUTCOME MEASURES AND RESULTS

In group 1, 86% of patients with severe vitamin D deficiency were diagnosed with threatened miscarriage, which is significantly higher than in group 3 (85.7% and 33.3%, χ² = 7.490, p = .007). At the same time, retrochorial hematoma in group 1 occurred 3.5 times more often than in group 3 (57.1% and 16.67%, respectively, χ² = 4.473, p = .035). Subsequently, every 4^th woman from the group with vitamin D deficiency gave birth earlier than expected, which was not observed among patients from group 3 (25%, 0%, χ² = 1.231, p = .268).

CONCLUSION

Prescribing cholecalciferol vitamin replacement therapy as part of complex preserving therapy for threatening miscarriage, followed by monitoring its blood level and deviating from normal parameters, contributing to a favorable course of pregnancy and improving perinatal outcomes.

The optimal cut-off point of vitamin D for pregnancy outcomes using a generalized additive model

BACKGROUND & AIM

Several studies consider vitamin D deficiency as a modifiable risk factor for adverse pregnancy outcomes. However, there is no specific cut-off point for the serum level of this prohormone to identify high-risk pregnant women. This study aimed to determine the thresholds for the circulating levels of 25-hydroxyvitamin D (25(OH)D), associated with adverse pregnancy outcomes, including preterm labor, preeclampsia (PE), and gestational diabetes mellitus (GDM), using a generalized additive model.

METHODS

This is a descriptive and analytical cross-sectional study carried out on the data collected from the Khuzestan Vitamin D Deficiency Screening Program in Pregnancy. Of 1800 pregnant women, referred to the health centers of Masjed-Soleyman and Shushtar (Khuzestan Province, Iran), we used the data of 1763 pregnant women, whose serum vitamin D status during the third trimester of pregnancy was available. The datasets were randomly divided into training (70%) and validation (30%) subsets. The cut-off levels of 25(OH)D were identified for the low, moderate, and high risk of adverse pregnancy outcomes, according to generalized additive models (GAM) with smooth functions in the training data set. Then Generalized Linear Model (GLM), with logit link function was applied in the validation dataset to explore the relationships between the optimal vitamin D classification and adverse pregnancy outcomes after adjusting for the potential confounders.

RESULTS

The optimal cut-off levels of 25(OH)D for the high, moderate, and low risk of GDM were ≤16, 16-26, and >26 ng/mL, respectively. Also, the optimal cut-off points of 25(OH)D for the high, moderate, and low risk of preterm delivery were ≤15, 15-21, and >21 ng/mL, respectively. Finally, the corresponding values for the high, moderate, and low risk of PE were ≤15, 15-23, and >23 ng/mL, respectively. The models were well-calibrated, based on the Hosmer-Lemeshow test. Results of the adjusted generalized linear model showed a significant increasing trend in the risk of pregnancy outcomes by decreasing 25(OH)D levels.

CONCLUSION

In the preconception period, a 25(OH)D cut-off level of >15 ng/mL is recommended for the prevention of adverse pregnancy outcomes.

Association between vitamin D plasma concentrations and VDR gene variants and the risk of premature birth

Background

Premature birth is the main cause of mortality in children under 1 year, and vitamin D deficiency during gestation is associated with prematurity. The effects of vitamin D are mediated by its receptor, which is encoded by the VDR gene. VDR variants—such as single nucleotide variation (SNV)—are associated with increased risk of prematurity, but there are conflicting results. We evaluated serum vitamin D concentrations and the frequency of TaqI/A > G, BsmI/C > T, ApaI/C > A, and FokI/A > T VDR variants in mothers and preterm (PTN) and full-term (FTN) newborns.

Methods

We conducted a case-control study comprising 40 pairs of mothers and their PTNs (gestational age < 32 weeks and/or weight < 1500 g), and 92 pairs of mothers and FTNs as controls. Genotyping was performed by real-time PCR, and plasma vitamin D concentrations were measured by electrochemiluminescence.

Results

Vitamin D levels were significantly lower in PTN mothers. Genotypes TaqI/GG and BsmI/TT, and haplotypes AAG (TaqI/A-ApaI/A-FokI/G) and GCA (TaqI/G-ApaI/C-FokI/A) were significantly more frequent in PTN mothers, and genotypes TaqI/AG, ApaI/AA, and FokI/AG resulted in significantly lower vitamin D levels. Genotypes BsmI/TT and ApaI/AA were associated with vitamin D deficiency and 2.36 and 7.99 times greater likelihood of PTB, respectively. Vitamin D levels were also lower in PTNs, although it was not statistically significant. Genotypes BsmI/TT, ApaI/AA, and FokI/GG, and haplotype GAG (TaqI/G-ApaI/A-FokI/G) were significantly more frequent in PTNs. Those with FokI/GG genotypes had significantly lower vitamin D levels.

Conclusions

VDR variants contribute to variations in vitamin D concentrations and the increased risk of prematurity.