Maternal-fetal vitamin D receptor polymorphisms significantly associated with preterm birth

Maternal genetic risk factors for spontaneous preterm birth: A systematic review and meta-analysis

BACKGROUND

Despite various genomic approaches used in prior studies investigating the association of maternal genetic variability with spontaneous preterm birth (sPTB), results show inconsistency and contradictions.

OBJECTIVES

To conduct a systematic review of studies analyzing the association between maternal genetic variants and sPTB, evaluate retrieved studies based on selection criteria, classify studies into hypothesis-based and hypothesis-free, and perform a meta-analysis to identify the strongest associations.

SEARCH STRATEGY

PubMed, Scopus, and reference lists were searched until October 2024.

SELECTION CRITERIA

English-language, case-control, cross-sectional, and prospective cohort studies examining the association between maternal genetic variations and sPTB were included.

DATA COLLECTION AND ANALYSIS

Data on authors, publication year, ethnicity, genes/variants, P values, study type, sample size, inclusion criteria, and methods were collected. The association strength was estimated using odds ratios with 95% confidence intervals.

RESULTS

Eighty-one studies met eligibility criteria: 73 utilized a hypothesis-based and 14 a hypothesis-free approach. Thirty-five studies qualified for a meta-analysis, revealing a significant association in tumor necrosis factor α (rs1800629) gene for alleles and additive and recessive genetic models (P ≤ 0.05). From the hypothesis-free approach, 13 genes reached global significance in association with sPTB (P < 5 × 10-8).

CONCLUSIONS

No single gene or variant was consistently associated with sPTB risk among studies. Hypothesis-based analyses highlighted tumor necrosis factor α (rs1800629) as a modest signal, while hypothesis-free approaches identified 13 genes with genome-wide significance, pointing to new research directions in understanding sPTB genetics.

Association of 25(OH)-Vitamin D3 Serum Concentrations and Vitamin D Receptor Gene Variants with the Risk of Idiopathic Spontaneous Preterm Birth in the Croatian Population

Preterm birth (PTB) forms a heterogeneous group with possible genetic predisposition. 25(OH)-vitamin D3 plays a significant role during implantation, placentation, and the maintenance of normal pregnancy. The aim of our research was to examine whether FokI, Cdx2, and ApaI VDR gene variants, as well as serum concentrations of 25-hydroxy25(OH)-vitamin D3 in women and their newborns, might be predisposing factors for idiopathic spontaneous preterm birth. The patient group consisted of 44 pairs of women with ISPTB and their children, and the control group consisted of 44 pairs of women who delivered at term and their children. At the time of delivery, peripheral blood was collected from every woman, and after newborn delivery, umbilical cord blood was collected. For genotyping of the rs2228570 C/T, rs11568820 G/A, and rs7975232 T/G SNPs, a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) was used. Serum concentrations of 25(OH)-vitamin D3 were determined using high-performance liquid chromatography (HPLC). There were no statistically significant differences in the frequencies of VDR genotypes and alleles between women with ISPTB and control women. There was a statistically significant difference in the distribution of VDR Cdx-2 (rs11568820) genotypes between preterm-born children and controls, with the GG genotype and G allele being more prevalent among patients than controls (p < 0.001). There were no statistically significant differences in mean values between women with ISPTB and control women, nor between preterm and full-term newborns, although the 25(OH)-vitamin D3 concentrations in preterm-born children were lower than in controls. Furthermore, there was a statistically significant correlation in 25(OH)-vitamin D3 concentrations between mothers and children both in the patient and in the control groups (b = 0.771, p < 0.001). The results of our study demonstrate a notable association between the VDR Cdx2 gene polymorphism and idiopathic spontaneous preterm birth (ISPTB) in a Caucasian population, but because of the small number of participants, further research is needed.

Association of vitamin D receptor genetic polymorphisms with the risk of infertility: a systematic review and meta-analysis

BACKGROUND

The causes of infertility have remained an important challenge. The relationship between VDR gene polymorphisms and infertility has been reported, with controversial findings.

OBJECTIVE AND RATIONALE

We aimed to determine this relationship by conducting a systematic review and meta-analysis.

SEARCH METHODS

The study was started with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) declaration and the final draft was registered as a protocol in PROSPERO (ID: CRD42023416535). The international electronic databases including PubMed (Medline), Scopus, Web of Sciences, and Cumulative Index to Nursing and Allied Health Literature (CINHAL) were searched until January 30, 2023, by using appropriate keywords. The quality of the final studies was assessed using the NOS Checklist for case-control studies. The odds ratios (ORs) for each of the genetic models were pooled, and a subgroup analysis based on geographical region and types of infertility was carried out by the MetaGenyo online tool.

OUTCOMES

Case-control studies including 18 and 2 studies about infertility in women and men, respectively, and 4 miscarriage studies were entered into the meta-analysis. The VDR gene TaqI polymorphism was associated with infertility susceptibility in women in the allele contrast [OR = 1.2065, 95% CI (1.0846-1.3421); P = 0.0005], Recessive model [OR = 1.3836, 95% CI (1.1197-1.7096); P = 0.002], Dominant model [OR = 1.2146, 95% CI (0.0484-1.4072); P = 0.009], Homozygote [OR = 1.4596, 95% CI (1.1627-1.8325); P = 0.001], and TT vs. Tt [OR = 1.2853, 95% CI (1.0249-1.6117); P = 0.029. ApaI and FokI gene polymorphisms were found to be significantly protective SNPs against women and men infertility in the Dominant model [OR = 0.8379, 95% CI (0.7039- 0.9975); P = 0.046] and Recessive model [OR = 0.421, 95% CI (0.1821-0.9767); P = 0.043], respectively. Sub-group meta-analysis showed a protection association of ApaI in dominant [OR = 0.7738, 95% CI = 0.6249-0.9580; P = 0.018] and AA vs. aa [OR = 0.7404, 95 CI% (0.5860-0.9353) P = 0.011725] models in PCOS subgroup, however, a negative association with idiopathic infertility was found in AA vs. Aa [OR = 1.7063, 95% CI (1.1039-2.6375); P = 0.016187] and Aa vs. aa [OR = 0.6069, 95% CI (0.3761-0.9792); P = 0.040754]. TaqI SNP was significantly associated with infertility in the African population and BsmI was associated with the disease mostly in the Asian population.

CONCLUSION

This meta-analysis showed that the TaqI polymorphism may be linked to women's infertility susceptibility. However, ApaI and FokI might be the protective SNPs against infertility in Women and men, respectively.

The Effect of Maternal Dietary Patterns on Birth Weight for Gestational Age: Findings from the MAMI-MED Cohort

Limited evidence exists on the effects of maternal dietary patterns on birth weight, and most studies conducted so far did not adjust their findings for gestational age and sex, leading to potentially biased conclusions. In the present study, we applied a novel method, namely the clustering on principal components, to derive dietary patterns among 667 pregnant women from Catania (Italy) and to evaluate the associations with birth weight for gestational age. We identified two clusters reflecting distinct dietary patterns: the first one was mainly characterized by plant-based foods (e.g., potatoes, cooked and raw vegetables, legumes, soup, fruits, nuts, rice, wholemeal bread), fish and white meat, eggs, butter and margarine, coffee and tea; the second one consisted mainly of junk foods (sweets, dips, salty snacks, and fries), pasta, white bread, milk, vegetable and olive oils. Regarding small gestational age births, the main predictors were employment status and primiparity, but not the adherence to dietary patterns. By contrast, women belonging to cluster 2 had higher odds of large for gestational age (LGA) births than those belonging to cluster 1 (OR = 2.213; 95%CI = 1.047-4.679; p = 0.038). Moreover, the odds of LGA increased by nearly 11% for each one-unit increase in pregestational BMI (OR = 1.107; 95%CI = 1.053-1.163; p < 0.001). To our knowledge, the present study is the first to highlight a relationship between adherence to an unhealthy dietary pattern and the likelihood of giving birth to a LGA newborn. This evidence adds to the current knowledge about the effects of diet on birth weight, which, however, remains limited and controversial.

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.

Impact of maternal dietary carbohydrate intake and vitamin D-related genetic risk score on birth length: the Vitamin D Pregnant Mother (VDPM) cohort study

Background

Our objectives were to investigate the relationship between maternal vitamin D status and IGF-1 levels in healthy Minangkabau pregnant mothers and their impact on newborn anthropometry outcomes and to examine whether this relationship was modified by dietary intake using a nutrigenetic approach.

Methods

Healthy singleton pregnant mother and infant pairs (n = 183) were recruited. We created three genetic risk scores (GRSs): a six-SNP GRS based on six vitamin D-related single nucleotide polymorphisms (SNPs) involved in the synthesis of vitamin D (vitamin D-GRS), a two-SNP GRS using SNPs in VDR genes (VDR-GRS) and a four-SNP GRS using SNPs from DHCR7, GC, CYP24A1 and CYP2R1 genes (non-VDR GRS). The effect of the GRSs on IGF-1, vitamin D and newborn anthropometry and the interaction between the GRSs and dietary factors were tested using linear regression analysis.

Results

The vitamin D- and non-VDR GRSs were significantly associated with lower 25(OH)D concentration (p = 0.005 and p = 0.001, respectively); however, there was no significant association with IGF-1, and newborn anthropometry outcomes. However, there was a significant interaction of VDR-GRS with carbohydrate intake on birth length outcome (P_interaction = 0.032). Pregnant mothers who had higher carbohydrate intake (405.88 ± 57.16 g/day) and who carried ≥ 2 risk alleles of VDR-GRS gave birth to babies with significantly lower birth lengths compared to babies born to mothers with < 2 risk alleles (p = 0.008).

Conclusion

This study identified a novel interaction between VDR-GRS and carbohydrate intake on birth length outcome. These findings suggest that reducing the intake of carbohydrates during pregnancy, particularly for those who have a higher genetic susceptibility, might be an effective approach for preventing foetal growth abnormalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05020-3.

Dietary Intake and Genetic Background Influence Vitamin Needs during Pregnancy

Numerous approaches demonstrate how nutritional intake can be sufficient to ensure the necessary supply of vitamins. However, it is evident that not all vitamins are contained in all foods, so it is necessary either to combine different food groups or to use a vitamin supplement to be well-fed. During pregnancy, deficiencies are often exacerbated due to increased energy and nutritional demands, causing adverse outcomes in mother and child. Micronutrient supplementation could lead to optimal pregnancy outcomes being essential for proper metabolic activities that are involved in tissue growth and functioning in the developing fetus. In order to establish adequate vitamin supplementation, various conditions should be considered, such as metabolism, nutrition and genetic elements. This review accurately evaluated vitamin requirements and possible toxic effects during pregnancy. Much attention was given to investigate the mechanisms of cell response and risk assessment of practical applications to improve quality of life. Importantly, genetic studies suggest that common allelic variants and polymorphisms may play an important role in vitamin metabolism during pregnancy. Changes in gene expression of different proteins involved in micronutrients’ metabolism may influence the physiological needs of the pregnant woman.

Relationship between maternal vitamin D status in the first trimester of pregnancy and maternal and neonatal outcomes: a retrospective single center study

Background

This study aimed to investigate the relationship between maternal serum vitamin D status in the first trimester of pregnancy and maternal as well as neonatal outcomes, considered the prevalence of vitamin D deficiency (serum 25(OH)D < 50 nmol/L) around the world, especially in the pregnant women.

Methods

From January 2015 to December 2016, in this cross-sectional retrospective study, we enrolled women receiving regular prenatal examinations and giving birth in the International Peace Maternity and Child Health Hospital. Cases confirmed as multiple pregnancy, incomplete medical records, and vitamin D level recorded after 13 weeks of gestation were excluded. A total of 23,394 mother-infant pairs were included ultimately. Obstetric and neonatal information were extracted from the database. Maternal serum vitamin D concentration was measured by chemiluminescence microparticle immunoassay. Logistic regression analysis (unadjusted and adjusted models) was used to analyze the association between vitamin D and maternal and neonatal outcomes.

Results

The average 25(OH) D concentration was 43.20 ± 0.10 nmol/L; 67.09% of patients were vitamin D deficient(25(OH) D < 50.00 nmol/L), 29.84% were vitamin D insufficient (50 nmol/L ≤ 25(OH)D < 75 nmol/L), 3.07% were sufficient (25(OH)D ≥ 75 nmol/L). The maternal 25(OH)D levels varied with age, pre-pregnancy BMI, season when blood sample was collected, number of previous-pregnancy. Notably, newborns delivered by women with deficient vitamin D status had a higher incidence rate of admission to NICU (Deficiency: 12.20% vs Insufficiency: 10.90% vs Sufficiency: 11.70%, P_bonferroni = .002) and a longer stay (deficiency: 6.2 ± 4.1 days vs insufficiency: 5.9 ± 3.1 days vs sufficiency: 5.1 ± 2.1 days, P_bonferroni = .010). Moreover, maternal vitamin D deficiency was a dependent risk factor for admission to NICU (unadjusted OR = 1.35, 95% CI,1.05–1.74 P_bonferroni = .022; adjusted OR = 1.31, 95% CI,1.010–1.687 P_bonferroni = .042).

Conclusions

Maternal vitamin D deficiency (25(OH) D < 50 nmol/L) was prevalent in eastern coastal China. The incidence rate of GDM as well as preeclampsia was higher in vitamin D insufficient group while vitamin D deficiency group was liable to intrauterine infection when compared with the other two groups. Most importantly, low vitamin D status in the first trimester of pregnancy was a dependent risk factor for admission to NICU. More well-designed perspective researches are necessary to clarify the role of vitamin D in the early stage of pregnancy.

Gene Variants Determine Placental Transfer of Perfluoroalkyl Substances (PFAS), Mercury (Hg) and Lead (Pb), and Birth Outcome: Findings From the UmMuKi Bratislava-Vienna Study

Prenatal exposure to perfluoroalkyl substances (PFAS), bisphenol A (BPA), lead (Pb), total mercury (THg), and methylmercury (MeHg) can affect fetal development. Factors influencing placental transfer rate of these toxins are poorly investigated. Whether prenatal exposure to pollutants has an effect on birth weight is incompletely understood. We therefore aimed (1) to determine placental transfer rates of PFAS, BPA, Pb, THg, and MeHg, (2) to analyze relationships between fetal exposure and birth outcome and (3) to analyze gene variants as mediators of placental transfer rates and birth outcome. Two hundred healthy pregnant women and their newborns participated in the study. BPA, 16 PFAS, THg, MeHg, and Pb were determined using HPLCMS/MS (BPA, PFAS), HPLC-CV-ICPMS (MeHg), CV-AFS (THg), and GF-AAS (Pb). Questionnaires and medical records were used to survey exposure sources and birth outcome. 20 single nucleotide polymorphisms and two deletion polymorphisms were determined by real-time PCR from both maternal and newborn blood. Genotype-phenotype associations were analyzed by categorical regression and logistic regression analysis. Specific gene variants were associated with altered placental transfer of PFAS (ALAD Lys59Asn, ABCG2 Gln141Lys), THg (UGT Tyr85Asp, GSTT1del, ABCC1 rs246221) and Pb (GSTP1 Ala114Val). A certain combination of three gene polymorphisms (ABCC1 rs246221, GCLM rs41303970, HFE His63Asp) was over-represented in newborns small for gestational age. 36% of Austrian and 75% of Slovakian mothers had levels exceeding the HBM guidance value I (2 μg/L) of the German HBM Commission for PFOA. 13% of newborns and 39% of women had Ery-Pb levels above 24 μg/kg, an approximation for the BMDL₀₁ of 12 μg/L set by the European Food Safety Authority (EFSA). Our findings point to the need to minimize perinatal exposures to protect fetal health, especially those genetically predisposed to increased transplacental exposure.

Vitamin D receptor gene polymorphisms and haplotypes in the etiology of recurrent miscarriages

A few years ago it was shown that disturbed metabolism of the vitamin D/receptor (VD/VDR) complex may be important in the etiology of spontaneous abortion, as well as in the etiology of recurrent miscarriages (RM). The goal of this study was to investigate the association between four maternal VDR polymorphisms as well as haplotypes settings and RM occurrence in a Polish population of women in reproductive age. A total of 230 women were recruited to this study (110 with RM, 120 consecutively recruited age-matched healthy women with at least two full-term pregnancies and with no history of miscarriages). DNA samples were genotyped for VDR polymorphisms: FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232) and TaqI (rs731236). Significant differences in genotype distributions and allele frequencies between case and control groups were observed in VDR BsmI polymorphism (GG vs. GA and AA, OR = 0.56, p = 0.036 and OR = 1.49, p = 0.035, respectively). The best evidence of an association with RM prevention was observed for the TTGT haplotype, which was more frequent among controls than cases even after permutation test (0.09 vs. 0.017, p = 0.0024). Other haplotypes were also significantly more frequent in the control group: TGT (rs7975232, rs1544410, rs2228570), TG (rs7975232, rs1544410), TTG (rs731236, rs7975232, rs1544410), TT (rs731236, rs7975232). Our research indicated the possible role of VDR BsmI genetic polymorphism in RM etiology, suggesting at the same time the active role of maternal VD metabolism and its influence on pregnancy outcome. The significant influence of several maternal haplotypes was shown to prevent RM occurrence.

A genetic approach to study the relationship between maternal Vitamin D status and newborn anthropometry measurements: the Vitamin D pregnant mother (VDPM) cohort study

PURPOSE

Adverse effects of maternal vitamin D deficiency have been linked to adverse pregnancy outcomes. We investigated the relationship between maternal vitamin D status and newborn anthropometry measurements using a genetic approach and examined the interaction between genetic variations in involved in vitamin D synthesis and metabolism and maternal vitamin D concentrations on newborn anthropometry.

METHODS

The study was conducted in 183 pregnant Indonesian Minangkabau women. Genetic risk scores (GRSs) were created using six vitamin D-related single nucleotide polymorphisms and their association with 25-hydroxyvitamin D [25(OH)D] levels and newborn anthropometry (183 infants) were investigated.

RESULTS

There was no significant association between maternal 25(OH)D concentrations and newborn anthropometry measurements (P > 0.05, for all comparisons). After correction for multiple testing using Bonferroni correction, GRS was significantly associated with 25(OH)D in the third trimester (P = 0.004). There was no association between GRS and newborn anthropometric measurements; however, there was an interaction between GRS and 25(OH)D on head circumference (P = 0.030), where mothers of neonates with head circumference < 35 cm had significantly lower 25(OH)D if they carried ≥4 risk alleles compared to those who carried ≤3 risk alleles.

CONCLUSION

Our findings demonstrate the impact of vitamin D-related GRS on 25(OH)D and provides evidence for the effect of vitamin D-related GRS on newborn anthropometry through the influence of serum 25(OH)D levels among Indonesian pregnant women. Even though our study is a prospective cohort, before the implementation of vitamin D supplementation programs in Indonesia to prevent adverse pregnancy outcomes, further large studies are required to confirm our findings.

Vitamin D receptor Fokl polymorphism is a determinant of both maternal and neonatal vitamin D concentrations at birth

Maternal vitamin D deficiency is considered to be the key determinant of the development of neonatal vitamin D deficiency at birth and during early infancy. Specific vitamin D receptor (VDR) gene polymorphisms have been associated with adverse pregnancy and offspring outcomes. The aim of this study was to evaluate the effect of maternal and neonatal VDR polymorphisms (ApaI, TaqI, BsmI, FokI, Tru9I) on maternal and neonatal vitamin D status. VDR polymorphisms were genotyped in 70 mother-neonate pairs of Greek origin, and classified according to international thresholds for Vitamin D status. Mean neonatal and maternal 25-hydroxy-vitamin D [25(OH)D] concentrations were 35 ± 20 and 47 ± 26 nmol/l, respectively. Neonatal VDR polymorphisms were not associated with neonatal 25(OH)D concentrations. In contrast, mothers with the Fokl FF polymorphism had a 70 % lower risk of vitamin D deficiency [25(OH)D <30 nmol/l] compared with ff ones, after adjustment for several confounders. They were also in 73 % and 88 % lower risk of giving birth to vitamin D deficient [25(OH)D <30 nmol/l] neonates compared with Ff and ff mothers, respectively. These results suggest a protective role of maternal Fokl FF genotype against both maternal and neonatal vitamin D deficiency. Further studies are needed to clarify the complex gene-gene and gene-environment interactions that determine vitamin D status at birth.

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.

Vitamin D Status in Pregnant Women in Southern China and Risk of Preterm Birth: A Large-Scale Retrospective Cohort Study

Background

The influence of maternal vitamin D on pregnancy outcomes, including preterm birth (PTB), is unclear due to different experimental designs and study populations (patient race and sample size) of previous studies. We aimed to investigate the relationship between 25-hydroxyvitamin D (25[OH] D) levels and PTB among pregnant women in southern China.

Material/Methods

A total of 11 641 pregnant women were retrospectively enrolled between January 2016 and April 2019. Vitamin D concentrations were evaluated by electrochemiluminescence immunoassay. Logistic regression analysis was used to analyze the association between vitamin D and PTB.

Results

The average 25(OH) D concentration was 59.3±21.5 nmol/L; 34.8% of patients were vitamin D deficient, 43.0% were vitamin D insufficient (25[OH] D <50 nmol/L and 50–74.9 nmol/L, respectively). In total, 3.6% of newborns were born prematurely. Comparing the pre-term and full-term groups, 45.7% versus 42.9% and 29.8% versus 35% were vitamin D deficient and insufficient, respectively These differences were not significant (P>0.05). However, the mean vitamin D status was significantly different between the pre-term and full-term groups (61.3±21.3 and 59.1±21.5 nmol/L, respectively). No association was found between vitamin D deficiency/insufficiency and PTB in unadjusted or adjusted models, compared with vitamin D sufficiency (adjusted odds ratio, 1.016; 95% confidence interval, 0.794–1.301 and 0.842; 0.641–1.106, respectively).

Conclusions

Low maternal 25(OH) D levels are common in southern China. However, low vitamin D status in pregnant women appears to be unrelated to PTB. Measuring vitamin D level alone is therefore not sufficient to predict PTB.

Genetic variation in the maternal vitamin D receptor FokI gene as a risk factor for recurrent pregnancy loss

PURPOSE

Recurrent pregnancy loss (RPL) is a reproductive disorder defined as the loss of two or more pregnancies before 24 weeks of gestation. Despite the fact that several mechanisms have been previously described for the pathogenesis of RPL, the causes of ∼50% of cases remain unknown. However, recent studies indicate association of vitamin D deficiency with adverse pregnancy outcome, including RPL. The vitamin D receptor (VDR) is a crucial mediator of the pleiotropic cellular effects of vitamin D. Its function is influenced by several single nucleotide polymorphisms (SNPs). The main objective of this study is to assess whether maternal VDR SNPs are associated with the risk of RPL in Slovenian and Croatian women.

METHODS

A case-control study including 320 women with RPL and control women is designed to examine the potential association of VDR polymorphisms (FokI rs222857, Cdx2 rs11568820, and Taq1 rs731236) with RPL. Genotyping is performed using polymerase chain reaction and restriction fragment length polymorphism methods.

RESULTS

We find a statistically significant higher frequency of the rs222857 CC genotype (χ² = 6.61, p = .036) and C allele (χ² = 5.93, p = .015) in RPL women compared to controls. Subsequently, the odds for RPL for the rs222857 are increased under the recessive (CCvsCT + TT: OR = 1.78; 95% CI = 1.12-2.82; p = .015) and the codominant (CCvsTT: OR = 2.21; 95% CI = 1.08-4.53; p = .029; CCvsCT: OR = 1.68; 95% CI = 1.04-2.72; p = .036) genetic models. The other two analyzed polymorphisms did not show any statistical significant result.

CONCLUSIONS

Our results suggest that variations in the maternal VDR FokI gene might be associated with RPL in Slovenian and Croatian women.

Polymorphism in the vitamin D receptor gene is associated with maternal vitamin D concentration and neonatal outcomes: A Brazilian cohort study

OBJECTIVES

This study evaluated the associations between single-nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) gene, maternal vitamin D concentration, and gestational outcomes.

METHODS

The cohort consisted of 270 pregnant women who received prenatal services at basic public healthcare centers in the city of Santo Antônio de Jesus, Bahia, Brazil. For statistical analysis, multiple linear regression was used.

RESULTS

A mean of 72.62 (SD = 31.51) nmol/L for 25-hydroxyvitamin D (25(OH)D) concentrations was found. The mean birth weight was 3.340 g (SD = 0.545 g), and the mean duration of gestation was 38.66 (SD = 1.83) weeks. Pregnant women who were homozygous for the low-frequency allele GG of SNP TaqI had a higher concentration of vitamin D during gestation (β = 14.09 nmol/L; 95% CI = 0.85, 27.34) than the higher frequency homozygotes AA (β = 3.33 nmol/L; 95% CI = -4.37, 11.05). The children of heterozygous women for the ApaI SNP (GA) were born with a lower weight (β = -131.99 g, 95% CI = -258.50, -5.47, P = .04). The heterozygote genotype of the SNP TaqI (CA) decreased the risk of short duration of gestation (β = 0.54 weeks, 95% CI = 0.09, 0.99, P = .01), and the homozygote for the lower frequency allele in the SNP ApaI (CC) showed a negative effect, decreasing the duration of gestation (β = -0.69 weeks, 95% CI = -1.35, -0.26, P = .04).

CONCLUSIONS

The VDR gene is an important genetic predictor of a higher concentration of vitamin D during gestation, low birth weight, and decreasing duration of gestation.

The possible role of maternal and placental vitamin D receptor polymorphisms and haplotypes in pathogenesis of preeclampsia

Purpose: Vitamin D deficiency may be a main causative agent in the pathogenesis of preeclampsia (PE). The actions of the active form of vitamin D are mediated via the vitamin D receptor (VDR), which is expressed in numerous organs including placenta. Therefore, we evaluated the potential relationship between maternal and placental VDR polymorphisms and the predisposition to PE in an Iranian population.Methods: This case-control study surveyed 152 PE and 160 normotensive pregnant women. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was performed to examine the maternal and placental VDR Fok1 rs2228570, Bsm1 rs1544410, Taq1 rs731236, and Apa1 rs7975232 polymorphisms.Results: The maternal but not placental VDR FokI Ff genotype, was significantly lower in PE women (P = .02 and P = .06, respectively). The maternal and placental VDR FokI polymorphism was associated with lower PE risk in the dominant model (Ff+ff vs. FF) and these genotypes could decrease PE risk (OR, 0.5 [95% CI, 0.3-0.8], P = .007 and OR, 0.5 [95% CI, 0.3-0.9], P = .02, respectively). The haplotype analysis revealed that the maternal and placental TABf haplotype may lead to decreased risk of PE. In addition, the placental TABF haplotype was associated with higher risk of PE. No relationship was observed between PE susceptibility and the maternal and placental VDR Bsm1, Taq1 and Apa1 polymorphisms. There was also no relationship between the maternal and placental VDR polymorphisms and PE severity.Conclusions: the maternal and placental VDR FokI variant was associated with decreased risk of PE in the dominant model.

Single Nucleotide Polymorphisms in Vitamin D Receptor Gene Affect Birth Weight and the Risk of Preterm Birth: Results From the "Mamma & Bambino" Cohort and A Meta-Analysis

The effect of vitamin D receptor gene (VDR) polymorphisms on adverse pregnancy outcomes—including preterm birth (PTB), low birth weight and small for gestational age—is currently under debate. We investigated 187 mother-child pairs from the Italian “Mamma & Bambino” cohort to evaluate the association of maternal VDR polymorphisms—BsmI, ApaI, FokI and TaqI—with neonatal anthropometric measures and the risk of PTB. To corroborate our results, we conducted a meta-analysis of observational studies. For the FokI polymorphism, we showed that gestational duration and birth weight decreased with increasing number of A allele (p = 0.040 and p = 0.010, respectively). Compared to the GG and GA genotypes, mothers who carried the AA genotype exhibited higher PTB risk (OR = 12.049; 95% CI = 2.606–55.709; p = 0.001) after adjusting for covariates. The meta-analysis confirmed this association under the recessive model (OR = 3.67, 95%CI 1.18–11.43), and also pointed out the protective effect of BsmI polymorphism against the risk of PTB under the allelic (A vs. G: OR = 0.74; 95%CI 0.59–0.93) and recessive (AA vs. GG + AG: OR = 0.62; 95%CI 0.43–0.89) models. Our results suggest the association between some maternal VDR polymorphisms with neonatal anthropometric measures and the risk of PTB.

Role of Placental VDR Expression and Function in Common Late Pregnancy Disorders

Vitamin D, besides its classical role in bone metabolism, plays a distinct role in multiple pathways of the feto-maternal unit. Calcitriol is the major active ligand of the nuclear vitamin D receptor (VDR). The vitamin D receptor (VDR) is expressed in different uteroplacental parts and exerts a variety of functions in physiologic pregnancy. It regulates decidualisation and implantation, influences hormone secretion and placental immune modulations. This review highlights the role of the vitamin D receptor in physiologic and disturbed pregnancy, as preeclampsia, fetal growth restriction, gestational diabetes and preterm birth. We discuss the existing literature regarding common VDR polymorphisms in these pregnancy disorders.