Effect of the functional VEGFA-583C/T variant on vascular endothelial growth factor levels and the risk of recurrent spontaneous miscarriage

Association between cytokine polymorphisms and recurrent pregnancy loss: A review of current evidence

Cytokines are a type of protein that play an important role in the immune response and can also affect many physiological processes in the body. Cytokine polymorphisms refer to genetic variations or mutations that occur within the genes that code for cytokines, which may affect the level of cytokine production and function. Some cytokine polymorphisms have been associated with an increased risk of developing certain diseases, while others may be protective or have no significant effect on health. In recent years, the role of cytokine polymorphisms in the development of recurrent pregnancy loss (RPL) has been studied. RPL or miscarriage is defined as the occurrence of two or more consecutive pregnancy losses before the 20th week of gestation. There are diverse causes leading to RPL, including genetic, anatomical, hormonal, and immunological factors. With regard to cytokine polymorphisms, a few of them have been found to be associated with an increased risk of RPL, for instance, variations in the genes that code for interleukin-6, tumor necrosis factor-alpha, and interleukin-10. The exact mechanisms by which cytokine polymorphisms affect the risk of recurrent miscarriage are still being studied, and further research is essential to fully understand this complex condition. This brief review aims to summarize the recent literature on the association between cytokine polymorphisms and RPL.

Maternal candidate gene variants, epigenetic factors, and susceptibility to idiopathic recurrent pregnancy loss: A systematic review

BACKGROUND

Recurrent pregnancy loss is defined as the loss of two or more pregnancies and is a distressing condition for couples.

OBJECTIVE

To investigate the relationship between variants in the candidate susceptibility genes and epigenetic factors to identify risk factors for idiopathic recurrent pregnancy loss (iRPL).

SEARCH STRATEGY

A systematic literature search was performed using PubMed, Google Scholar, ScienceDirect, and Scopus databases. Insilico analysis was carried out using ShinyGO and STRING software.

SELECTION CRITERIA

Research papers examining the association between variations in genetic and epigenetic factors and iRPL.

DATA COLLECTION AND ANALYSIS

Data were independently extracted by two authors.

MAIN RESULTS

In total, 83 research papers were finally selected for the present study. Among all the genes involved in the pathogenesis of recurrent pregnancy loss, polymorphisms in IL superfamily genes, VEGF, ESR, and MTHFR were the most investigated.

CONCLUSION

Polymorphisms in angiogenesis, immune tolerance, and thrombophilia pathway genes, which occur independently or synergistically, may lead to various complications during fetal development. Identification of multi-allele risk variants and epigenetic factors in women will be helpful in the identification of high-risk pregnancies.

PROSPERO REGISTRATION NUMBER

Prospero CRD42021287315.

Lack of association between the VEGFA gene polymorphisms and preterm birth in Korean women

Preterm birth (PTB), a pregnancy-related disease, is defined as a birth before 37 weeks of gestation. It is a major cause of maternal mortality and morbidity worldwide, and its incidence rate is steadily increasing. Various genetic factors can contribute to the etiology of PTB. Vascular endothelial growth factor A (VEGFA) gene is an important angiogenic gene and its polymorphisms have been reported to be associated with PTB development. Therefore, we conducted a case-control study to evaluate the association between VEGFA rs699947, rs2010963, and rs3025039 polymorphisms and PTB in Korean women. A total of 271 subjects (116 patients with PTB and 155 women at ≥38 weeks of gestation) were analyzed in this study. The genotyping of VEGFA gene polymorphisms was performed using polymerase chain reaction- restriction fragment length polymorphism. No significant association between the patients with PTB and the control groups was confirmed. In the combination analysis, we found a significant association between PTB and VEGFA rs699947 CC-rs2010963 GG-rs3025039 CC combination (odds ratio, 3.77; 95% confidence interval, 1.091 to 13.032; p = 0.031). The VEGFA rs699947, rs2010963, and rs3025039 polymorphisms might have no genetic association with the pathogenesis of PTB in Korean women. However, the combination analysis indicates the possibility that VEGFA acts in PTB pathophysiology. Therefore, larger sample sets and replication studies are required to further elucidate our findings.

Impact of Interleukin-10 Promoter Region Polymorphisms on Recurrent Miscarriage: A Case-Control Approach

Background

Recurrent miscarriage (RM), defined as two or more consecutive miscarriages prior to the 20th week of gestation is characterised by multifactorial aetiology. The prevalence of RM varies from 0.8% to 13.5% amongst women of reproductive age. The aetiological basis of RM has been traced to chromosomal, anatomic, hormonal and immunologic factors while half of the cases remain idiopathic.

Aims

This study aimed to investigate the association of interleukin-10 (IL-10) polymorphisms with RM amongst the Indian population.

Settings and Design

The present study included a total of 414 individuals including RM women (n = 199) with two or more pregnancy losses and healthy women (n = 215) without any previous history of pregnancy loss were taken as the control group.

Materials and Methods

Demographic features and reproductive history of women with RM and healthy women were taken. Genotype analysis of IL-10 polymorphisms rs1800872 and rs1800896 was performed using the polymerase chain reaction (PCR) restriction fragment length polymorphism and amplification mutation refractory system PCR, respectively.

Statistical Analysis Used

Student's t-test was used to compare the demographic features and reproductive history amongst both groups. Pearson's Chi-square was used to calculate the Hardy-Weinberg equilibrium, allelic and genotypic frequencies. All the statistical analyses were performed using the SPSS (version 21, IBM SPSS, NY, USA).

Results

Our results suggested that the genotypic and allelic frequency of rs1800872 polymorphism did not differ significantly between RM cases and control women (P = 0.07 and P = 0.23, respectively). The GG genotype (P = 0.007) and G allele (P = 0.003) of rs1800896 were significantly associated with an increased risk of RM. A statistically significant difference was also found for the distribution of genetic models (dominant and co-dominant model) between both groups for rs1800896. However, haplotype analysis revealed that none of the haplotypes provides a risk for the progression of RM.

Conclusion

The study is the first of its kind from our region and provides baseline data on the genetics of RM.

Implications of VEGF gene sequence variations and its expression in recurrent pregnancy loss

RESEARCH QUESTION

What is the association between VEGF gene sequence variants and its mRNA expression in recurrent pregnancy loss (RPL)? Vascular endothelial growth factor (VEGF) has a prominent role in pregnancy and affects pregnancy outcome. The association of VEGF gene 1154G>A, 634G>C and 583C>T polymorphic variations with cases of RPL and full-term fertile women as controls was investigated.

DESIGN

Two hundred women with RPL and 240 women healthy controls were included. The restriction fragment length polymorphism method was used for genotyping and quantitative real-time polymerase chain reaction was used for analysis of mRNA expression.

RESULTS

In VEGF 1154G>A, significant differences were found in homozygous AA genotype between case and control participants. The variant allele A frequency was significantly more abundant in RPL cases (0.41) than controls (0.19) (P < 0.0001). Only RPL cases with the multi-generation family history of miscarriages and those without any history showed significant differences of combined genotype GA+AA (P < 0.0001). In VEGF 634 G>C, CC genotype and allele C showed significantly increased frequency in RPL cases compared with healthy controls (P < 0.0001). The association between VEGF-1154 G>A SNP and VEGF-A mRNA expression levels was significant in RPL cases (P = 0.004). The heterozygous genotype GA was significantly (P = 0.03) associated with upregulation and downregulation of VEGF mRNA, whereas the homozygous variant genotype AA only leads to low expression levels of VEGF mRNA in patients with RPL.

CONCLUSIONS

All the variants of VEGF play a vital role in an increased susceptibility to RPL. Also, VEGF-1154, AA genotypes are associated with its altered low mRNA expression in women with RPL and seem to affect pregnancy outcome.

Selected genetic causes of miscarriages

Approximately 15–25% of pregnancies end in spontaneous abortion, which is an expulsion from the mother body of the fetus weighing less than 500 g or before the 20th week of gestation. Determining abortions etiology is difficult due to its multifactorial character. Chromosomal abnormalities cause 38.6–80% of miscarriages. The largest group (93%) of chromosomal aberrations found in miscarried fetuses are numerical changes – aneuploidies and polyploidies. Much rarer (7%) are unbalanced structural aberrations, which can arise de novo or can be inherited from a carrier parent. In couples with spontaneous abortions, reciprocal chromosomal translocations (RCT) occur the most frequently, next are Robertsonian translocations and inversions. More complex chromosome abnormalities, e.g. double aneuploidies are found in 3.8% of fetuses. Another group of causes responsible for abortions are monogenic diseases of embryo or fetus resulting from autosomal dominant, autosomal recessive or X-linked mutations. Among mutations which may contribute to pregnancy loss are factor V Leiden gene mutations (c.1601G>A, earlier 1691G>A) and prothrombin gene mutation (c.97G>A, earlier 20210G>A). The research on mutations in candidate genes, eg.: ALOX15, CR1, CYP1A1, CYP17, CYP2D6, FOXP3, HLA-G, IL-6, KHDC3L, NLRP7, NOS3, PLK4, SYCP3, TLR3, TNF, TP53 and VEGFA is still ongoing.

Role of Vascular Endothelial Growth Factor (VEGF) in Human Embryo Implantation: Clinical Implications

Vascular endothelial growth factor (VEGF) is a well-known angiogenic factor that plays a critical role in various physiological and pathological processes. VEGF also contributes to the process of embryo implantation by enhancing embryo development, improving endometrial receptivity, and facilitating the interactions between the developing embryo and the endometrium. There is a correlation between the alteration of VEGF expression and reproductive failure, including recurrent implantation failure (RIF) and recurrent miscarriage (RM). In order to clarify the role of VEGF in embryo implantation, we reviewed recent literature concerning the expression and function of VEGF in the reproductive system around the time of embryo implantation and we provide a summary of the findings reported so far. We also explored the effects and the possible underlying mechanisms of action of VEGF in embryo implantation.

Association of vascular endothelial growth factor A polymorphisms and aberrant expression of connexin 43 and VEGFA with idiopathic recurrent spontaneous miscarriage

AIM

Idiopathic recurrent spontaneous miscarriage (IRSM) is one of the pregnancy outcomes that affects 1-2% of women trying to conceive. Specific genotype or aberrant expression of vascular endothelial growth factor A (VEGFA) and connexin 43 (Cx43) as two important genes for embryonic development are deemed to increase the risk of IRSM.

METHODS

To investigate any possible association of VEGFA polymorphisms and aberrant expression of Cx43 and VEGFA with IRSM, we carried out a case-control study including embryo chorionic villus tissues of 100 pregnant women with IRSM and 100 embryo chorionic villus tissues of healthy pregnant women without history of miscarriage. Restriction fragment length polymorphism was used for genotyping of rs699947 (-2578C/A) and rs2010963 (-634G/C) polymorphisms in VEGFA. Besides, quantitative real-time PCR was performed for VEGFA and Cx43 expression analysis.

RESULTS

The results showed that the frequency of -634G/C and C/C genotypes was significantly higher in aborted fetuses (P = 0.001 and P < 0.001, respectively) compared to the control group's. However, the frequency of -2578C/A genotypes was not significantly different between the cases and controls. Moreover, a significant higher expression of VEGF (P = 0.0005) and Cx43 (P = 0.0011) was observed in chorionic villus tissues of women with IRSM.

CONCLUSION

The finding demonstrated that IRSM frequency may depend on GC and CC genotypes of rs2010963 VEGF polymorphism and expression level of VEGF and Cx43 in IRSM patients was increased.

Case Control Study to Compare Serum Vascular Endothelial Growth Factor (VEGF) Level in Women with Recurrent Pregnancy Loss (RPL) Compared to Women with Term Pregnancy

INTRODUCTION

Recurrent pregnancy loss (RPL) is defined as three or more spontaneous pregnancy losses before the 20th week of gestation or fetal weight of < 500 gm from the last menstrual period. Vascular endothelial growth factor (VEGF) is essential for implantation, development of embryo and placental angiogenesis. Women with low VEGF level are believed to be at higher risk of RPL.

OBJECTIVE

To measure the level of VEGF in women with RPL and compare it with women with 1 or more successful pregnancies.

METHODS

This is a Case control study carried out in King George Medical University, Lucknow from August 2015 to 2016. Participants sample size was 60 women. Thirty women with 3 or more spontaneous abortions were included as cases, and 30 women with at least 1 successful term pregnancy were controls. Serum VEGF level was analyzed using ELISA kit. Main outcome measured: 1. Serum VEGF level in the two groups. 2. Serum VEGF level in different underlying etiologies in women with RPL.

RESULTS

Mean VEGF level was 105.3 pg/mL in RPL cases, while it was 156.8 pg/mL in fertile controls. (p = 0.01). VEGF level was 86.2 pg/mL in patients with anatomical defects, 109 pg/mL in APLA syndrome, 85.1 pg/mL in hypothyroidism and 122.2 pg/mL in unexplained RPL.

CONCLUSION

The mean serum VEGF level was significantly lower in women with recurrent pregnancy loss compared with women with successful term pregnancy, implicating its role in maintaining pregnancy.

Angiogenesis and oxidative stress-related gene variants in recurrent pregnancy loss

Recurrent pregnancy loss (RPL) affects ~3-5% of couples attempting to conceive and in around 50% of cases the aetiology remains unknown. Adequate vascularisation and placental circulation are indispensable for the development of a normal pregnancy. Prostaglandin-endoperoxide synthase 2 (PTGS2), vascular endothelial growth factor (VEGF) and the nitric oxide (NO) systems play important roles in reproductive physiology, participating in several steps including implantation and apoptosis of trophoblast cells. In this study we evaluated genetic polymorphisms in the inducible nitric oxide synthase (NOS2), PTGS2 and VEGFA genes as susceptibility factors for RPL. A case-control study was conducted in 149 women having two or more miscarriages and 208 controls. Allele and genotype distributions of the polymorphisms studied in the two groups were not statistically different. However, the dominant model showed that the presence of variant T (TT/GT) of rs2779249 (-1290G>T) of NOS2 was significantly associated with RPL (OR=1.58, CI 95%=1.03-2.44; P=0.037). The increased risk remained significant when adjusted for number of pregnancies, alcohol consumption and ethnicity (OR=1.92, CI95%=1.18-3.11; P=0.008). These results suggest that the variant genotypes of the functional polymorphism rs2779249 in the NOS2 promoter are a potential risk for RPL, possibly due to oxidative stress mechanisms.

Association of genetic polymorphisms in VEGF -460, -7 and -583 and hematocrit level with the development of idiopathic recurrent pregnancy loss and a meta-analysis

BACKGROUND

The present study was performed to investigate whether genetic variants of VEGF are associated with recurrent pregnancy loss (RPL) in Korean women and to provide insight into the role of VEGF in the pathogenesis of RPL development.

METHODS

A cohort of 384 women with idiopathic RPL with a history of two or more uxexplained consecutive early pregnancy losses and 236 control women were recruited from an infertility center of university-teaching hospital in Korea between March 1999 and February 2010. We examined three VEGF polymorphisms (rs833061, rs3025020 and rs25648). Genotyping was assessed by polymerase chain reaction (PCR)-restriction fragment length polymorphism analyses (rs3025020) or real-time PCR (rs833061, rs25648).

RESULTS

There was no statistically significant difference in frequency of each three VEGF polymorphic loci between the control and RPL groups. Allele combinations of VEGF rs3025020/rs833061 TT/TC and TT/TC + CC genotypes were associated with an increased frequency of RPL development [odds ratio (OR) = 3.525, 95% confidence interval (CI) = 1.154-10.767, p = 0.027 and OR = 3.815, 95% CI = 1.256-11.588, p = 0.018, respectively]. Haplotype analysis revealed that two allele combinations (rs833061/rs3025020 C-T and rs25648/rs3025020 T-T) were associated with an increased prevalence of RPL (OR = 2.548, 95% CI = 1.502-4.320, p = 0.0004 and OR = 16.50, 95% CI = 0.976-278.8, p = 0.003, respectively). Allele combinations and haplotypes of rs3025020/rs833061 were associated with maternal blood hematocrit (HCT) levels in the RPL group (p = 0.048 and 0.006, respectively).

CONCLUSIONS

The VEGF rs833061/rs3025020 genotype allele was related to the development of RPL and was also associated with maternal blood HCT levels in RPL patients. However, further studies are needed to clarify the exact mechanism of how VEGF and HCT are involved in RPL development.

The -2549 insertion/deletion polymorphism in the promoter region of VEGF is associated with the risk of recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is a common health problem affecting women of reproductive age. Altered expression of vascular endothelial growth factor (VEGF) has been associated with spontaneous abortion. The present case-control study aimed to evaluate the impact of the 18-bp insertion/deletion (ins/del) polymorphism (rs35569394) in the promoter region of the VEGF gene on idiopathic RSA. Genomic DNA from 93 patients with RSA and 93 healthy fertile women of southeastern Iran was isolated using the salting-out method. Genotyping of the rs35569394 variant was performed by a polymerase chain reaction (PCR) method. The findings indicated that the VEGF 18-bp ins/del variant significantly increased the risk of RSA under codominant (ins/ins vs. del/del; OR=2.85, 95% CI=1.31-6.22, P=0.019), dominant (del/ins+ins/ins vs. del/del; OR=2.19, 95% CI=1.20-4.01, P=0.015) and allelic (ins vs. del; OR=1.90, 95% CI=1.25-2.88, P=0.003) inheritance models. In summary, the findings propose a significant association between the VEGF 18-bp ins/del polymorphism and risk of RSA in a sample of the southeast Iranian population. Further studies on larger sample sizes and different ethnicities are required to validate the present findings.

Association of VEGFA gene polymorphisms and VEGFA plasma levels with spontaneous preterm birth

BACKGROUND

Angiogenic pathway regulating genes such as vascular endothelial growth factor A (VEGFA) have been implicated in preterm birth (PTB) complications. Research shows that the VEGFA/VEGF receptor system plays an important role in the regulation of circulating progesterone level. Attenuation of VEGFA signaling at mid pregnancy results in onset of labor and parturition because of a reduction in circulating progesterone levels. The aim of this study was to investigate the association of VEGFA gene polymorphisms (rs2010963, rs3025039, rs699947, and rs10434) with spontaneous PTB and VEGFA plasma levels in preterm and term women.

STUDY DESIGN

Peripheral maternal blood from 495 women was used for extraction of DNA and genotyping was carried out using the SequenomMassARRAY platform. Maternal plasma was used to measure VEGFA levels.

RESULTS

Results showed a significant association between rs2010963 variants and PTB at both allelic and genotypic levels. The frequencies of CG and GG genotypes were significantly higher in the preterm group (96%) than in the term group (87%) (P=0.012). The odds of the G allele occurring among the preterm group was 1.8 times higher than those in the term group (odds ratio 1.8, 95% confidence interval 1.2-2.6, P=0.003). After adjustment for Bonferroni correction, the association between rs2010963 variants and PTB remained significant (P=0.004). The rs69947 was associated with PTB at a nominal significance level (P=0.030). There was no significant association between rs3025039, rs10434, and PTB in this population. VEGFA gene polymorphisms were not associated with VEGFA plasma levels. This study indicated for the first time that the VEGFA rs2010963 polymorphisms may play a potential role in preterm complications.

Association of VEGF genetic polymorphisms with recurrent spontaneous abortion risk: a systematic review and meta-analysis

Background

Studies of the associations between the genetic polymorphisms of the vascular endothelial growth factor (VEGF) gene and recurrent spontaneous abortion (RSA) have revealed conflicting results. The present meta-analysis was performed to provide a more precise estimation of these relationships and to explore potential sources of heterogeneity that may have influenced the reported disparities.

Methods

An extensive literature search for relevant studies was conducted on PubMed, Embase, and The Cochrane Library through June 6, 2014. Crude odds ratio (OR) with 95% confidence intervals were calculated.

Results

10 case-control studies including 1,832 RSA patients and 2,271 healthy controls were identified. Meta-analysis indicated that rs1570360, rs3025039, rs2010963, and rs3025020 polymorphisms in the VEGF gene correlated with elevated RSA risk. The rs1570360 variant was statistically significantly relevant to RSA risk among non-Asian populations. Interestingly, the rs3025039 variant was statistically significantly relevant to RSA risk among Asian populations.

Conclusions

The current meta-analysis indicates that rs1570360, rs3025039, rs2010963, and rs3025020 polymorphisms increase RSA susceptibility. Moreover, rs1570360 and rs3025039 polymorphisms may play various roles in RSA susceptibility in various geographic groups.

Gene expression analysis of VEGF and its receptors and assessment of its serum level in unexplained recurrent spontaneous abortion

Objective

Unexplained recurrent spontaneous abortion (URSA) is one of the main complications of pregnancy which is usually defined as three or more consecutive pregnancy losses before the 20^th week of gestation without a known cause. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor and shown, along with its receptors (VEGFR1, 2), to play important roles in several physiologic processes including reproduction. The aim of the present study was to analyze gene expression of VEGF and VEGF receptors in endometrium of patients with a history of URSA compared with normal fertile women. In addition, serum VEGF concentration was assessed and compared between the two groups at the same time.

Materials and Methods

In this case control study, endometrial and blood samples were obtained between day 19^thand 24^th of menstrual cycle (window of implantation) from 10 women with a history of URSA (case group) and 6 fertile women who had at least one successful pregnancy (control group). Expression of VEGF and VEGFRs was studied by reverse transcription- polymerase chain reaction (RT-PCR) and then quantified by real time PCR. Normalization of expression levels was done by comparison with beta-actin expression level as an internal control. Relative VEGF, VEGFR1 and VEGFR2 expression quantities were compared between the two groups. Enzyme linked immunosorbent assay (ELISA) was used for serum VEGF assay.

Results

VEGF, VEGFR1 and VEGFR2 gene expression was detected in endometrial samples of both groups. The mean relative expression of VEGF gene was lower in the case group compared with control women, however, both VEGF receptors were expressed higher in endometrium of the case group. In addition, the serum level of VEGF was significantly higher in the case group compared with the controls.

Conclusion

Alteration in gene expression of VEGF and its receptors in endometrium and changes of serum VEGF might play important roles in pathogenesis of unexplained RSA.

Impact of VEGFA -583C > T polymorphism on serum VEGF levels and the susceptibility to acute chest syndrome in pediatric patients with sickle cell disease

We investigated the association of VEGFA -583C > T on VEGF serum levels and acute chest syndrome (ACS) in 351 pediatric patients with sickle cell disease (SCD), of whom 90 had ACS, and 261 were ACS-free controls. Significant differences in -583C > T minor allele and genotype frequencies were seen between ACS cases and controls, evidenced by enrichment of -583T/T genotypes in patients with ACS, which were linked with reduction in VEGF serum levels. VEGFA -583C > T and reduced VEGF serum levels may influence ACS risk in patients with SCD, which will aid in identifying patients with SCD who are at high risk of ACS.

Relationship between VEGFA polymorphisms and serum VEGF protein levels and recurrent spontaneous miscarriage

STUDY QUESTION

Is recurrent spontaneous miscarriage (RSM) associated with changes in vascular endothelial growth factor (VEGF) serum levels, and with polymorphisms in the VEGFA gene?

SUMMARY ANSWER

Reduced serum VEGF levels, and VEGFA -460T/C (rs833061), 398G/A (rs833068), -583T/C (rs3025020) variants, were associated with RSM.

WHAT IS KNOWN ALREADY

Reduced expression of VEGF has been linked with spontaneous miscarriage, likely due to defective fetal and placental angiogenesis. Since VEGF production is in part inherited, VEGFA polymorphisms associated with altered VEGF secretion have been investigated for their association with RSM, often with variable conclusions.

STUDY DESIGN, SIZE, DURATION

A retrospective case-control study, which was conducted between January 2011 and April 15, 2012.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Subjects comprised 296 women with RSM (mean age: 31.6 ± 5.4 year), and 305 age-matched (mean age: 31.6 ± 4.9 year) control Arab women, who had attended outpatient obstetrics and gynecology clinics in two teaching hospitals in Bahrain. VEGFA -2578C/A (rs699947), -460T/C (rs833061), -1154G/A (rs15703060), -634G/C (rs2010963), 398G/A (rs833068), 497G/A (rs833070), -583T/C (rs3025020) and 936C/T (rs3025039) genotyping was done by real-time PCR, with defined clusters; VEGF serum levels were measured by ELISA.

MAIN RESULTS AND THE ROLE OF CHANCE

Higher minor allele frequency (MAF) and genotype distribution of -460T/C [corrected P (Pc) = 0.003], 398G/A (Pc = 0.016) and -583T/C (Pc < 0.001) single nucleotide polymorphisms (SNPs) were seen in RSM cases than control women. Increased RSM risk was seen with homozygous -460T/C and 398G/A SNPs and with heterozygous -583T/C, which had a stronger effect when homozygous. Serum VEGF levels were significantly reduced in RSM cases compared with control women (P = 0.016), and correlated with -460T/C, 398G/A and -583T/C genotypes. Haploview analysis revealed heterogeneity in linkage disequilibrium between VEGFA variants, and two blocks were identified: Block 1 comprising -2578C/A, -460T/C and -1154G/A, while Block 2 contained -634G/C, 398G/A, 497G/A, -583T/C and 936C/T. Both negatively and positively RSM-associated 3-locus (Block 1) and 5-locus (Block 2) VEGFA haplotypes were identified, after controlling for a number of covariates.

LIMITATIONS, REASONS FOR CAUTION

The study was retrospective and can only demonstrate association and not a cause-effect relationship. Furthermore, it was limited to Bahraini Arabs,thereby necessitating parallel studies on other ethnic groups.

WIDER IMPLICATIONS OF THE FINDINGS

Reduced VEGF secretion, and specific VEGFA variants may contribute to the pathogenesis of RSM. However, the association of VEGFA SNPs with RSM appears to be independent of their association with altered VEGF serum levels. The differential association of VEGFA variants with RSM is in line with previous findings on the contribution of ethnicity/racial background to genetic association studies.