Reproduction   citetrack
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS  
Reproduction (2006) 131 395-401
DOI: 10.1530/rep.1.00815
Copyright © 2006 Society for Reproduction and Fertility
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Mtiraoui, N
Right arrow Articles by Mahjoub, T
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Mtiraoui, N
Right arrow Articles by Mahjoub, T

RESEARCH

Methylenetetrahydrofolate reductase C677T and A1298C polymorphism and changes in homocysteine concentrations in women with idiopathic recurrent pregnancy losses

N Mtiraoui, W Zammiti, L Ghazouani, N Jmili Braham, S Saidi, R R Finan1, W Y Almawi2 and T Mahjoub

Research Unit of Hematological and Autoimmune diseases, Faculty of Pharmacy, Monastir, Center University, Tunisia, 1 Faculté de Médecine, Université St Joseph, Beirut, Lebanon, and 2 Al-Jawhara Center for Molecular Medicine, Genetics and Inherited Diseases, College of Medicine & Medical Sciences, Arabian Gulf University, Manama, Bahrain

Correspondence should be addressed to W Y Almawi; Email: wyalmawi{at}yahoo.co.uk


   Abstract
Top
 Abstract
Introduction
 Subjects and Methods
 Results
 Discussion
 Acknowledgements
 References
 
Because they have been described as strong risk factors for idiopathic recurrent pregnancy losses (RPLs), we assessed the association between the methylenetetrahydrofolate reductase (MTHFR) single-nucleotide polymorphisms (SNPs) C677T and A1298C and hyperhomocysteinemia in Tunisian women with idiopathic RPL. Study subjects comprised 200 patients with more than three consecutive RPLs, and 200 age-matched parous control women. C677T and A1298C SNPs were analyzed by PCR-RFLP analysis, and fasting serum homocysteine was measured with ELISA. The frequency of MTHFR 677T/T (30.0 vs 7.0%) and 1298C/C (13.5 vs 4.0%) genotypes was significantly higher in patients. While it was similar among patients and controls (P = 0.095), higher homocysteine was seen with the T/T (but not 1298A/C and 1298C/C) genotype among patients and controls compared with non-T/T carriers (P < 0.05), and in patients vs controls. Higher prevalence of MTHFR 677T/T was seen in late (P < 0.05) and early-late (P < 0.001) RPL, while higher prevalence of 1298C/C genotype was seen only in early-late RPL (P < 0.001), and the prevalence of double heterozygotes was statistically not significant between patients and controls (P = 0.10; odds ratio = 2.73). Logistic regression analysis showed that, after adjusting for all variables, homozygosity for MTHFR C677T was associated with late (P < 0.001), and combined early-late (P < 0.001), while homozygosity for A1298C was associated only with combined early-late (P = 0.026), as was secondary-level education, which was associated with early (P = 0.005), late (P = 0.026) and combined early-late (P = 0.004) abortions. Homozygosity for MTHFR C677T (late and early-late) and A1298C (early-late) are risk factor for RPLs, irrespectively of total homocysteine levels.


   Introduction
Top
 Abstract
 Introduction
Subjects and Methods
 Results
 Discussion
 Acknowledgements
 References
 
Idiopathic recurrent pregnancy loss (RPL) is a frequent obstetric complication, and an estimated 1–2% women will present with three or more during their reproductive age, while almost 5% of women will present with two or more RPLs. While the exact cause of RPL remains undetermined in most of the cases, genetic predisposition to venous thrombosis (Finan et al. 2002), and elevation in total homocysteine (tHcy) levels (hyperhomocysteinemia) have been described as playing a role in the pathogenesis of RPL. The former was suggested to involve specific single-nucleotide polymorphisms (SNPs) in the genes coding for coagulation factors, including factor V-Leiden and prothrombin (G20210A), while the latter was described to be caused by mutations in methylenetetrahydrofolate reductase (MTHFR), in particular the C677T SNP (Nelen et al. 1998, Lissak et al. 1999, Wang et al. 2004).

MTHFR is critical in homocysteine (Hcy) metabolism, and catalyzes the NADPH-linked reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, and subsequently the vitamin B12-dependent methylation of Hcy to methionine (Jacques et al. 1996). A reduction in MTHFR level or activity by specific gene mutations induces hyperhomocysteinemia, characterized by mild-moderate increased plasma tHcy levels, and has been shown to be a risk factor for vascular thrombotic events, including coronary artery disease (Graham et al. 1997, Almawi et al. 2004a). While several mutations within it were described, the best-characterized MTHFR gene polymorphisms are the alanine-to-valine C677T (Frosst et al. 1995), and the glutamate-to-alanine A1298C (Van der Put et al. 1998) missense mutations. While both SNPs induce milder forms of MTHFR deficiency (Frosst et al. 1995, Chango et al. 2000), the A1298C SNP, located in the enzyme regulatory domain, unlike the C677T SNP which is found within the enzyme catalytic domain, does not result in either a thermolabile protein or increased tHcy (Hanson et al. 2001, Friso et al. 2002). Interestingly, 677CT/1298AC compound heterozygosity reportedly has similar clinical impact as C677T homozygosity (Chango et al. 2000, Chen et al. 2005).

Through their effect on tHcy levels, MTHFR mutations have been implicated as risk factors in the pathogenesis of RPL. This was highlighted by the findings that the prevalence of homozygous variants of both SNPs was higher among women with more than three idiopathic RPLs (Nelen et al. 1997, Quere et al. 1998, Sarig et al. 2002). Hyperhomocysteinemia caused by MTHFR mutations or folate deficiency was associated with placental abruption or infarction (Van der Molen et al. 2000), pre-eclampsia (Lachmeijer et al. 2001, Murakami et al. 2001), pregnancy-associated hypertension (Kosmas et al. 2004) and RPL (Nelen et al. 2000a, Unfried et al. 2002). Others failed to demonstrate any association between MTHFR SNPs, hyperhomocysteinemia and RPL (Foka et al. 2000, Makino et al. 2004), as similar (Holmes et al. 1999) or even lower (Makino et al. 2004) prevalence rates of MTHFR C677T SNP were seen in patients compared with women with uneventful pregnancies. This prompted us to assess the relationship between RPL, MTHFR C677T and A1298C SNPs and tHcy in 200 Tunisian women with three or more consecutive idiopathic miscarriages, compared with 200 parous women of similar ethnic background with uncomplicated pregnancies and deliveries.


   Subjects and Methods
Top
 Abstract
 Introduction
 Subjects and Methods
Results
 Discussion
 Acknowledgements
 References
 
Study subjects
This was a retrospective case-control study conducted in the maternity service of CHU Farhat Hached in Sousse, central Tunisia in the period 2001–2004. Cases comprised 200 women who had had three or more consecutive RPLs at 5–30 weeks of gestation (Table 1Go). RPLs were classified as early (5–10 weeks) or late (11–30 weeks). Exclusion criteria included induced abortions, infection, systemic diseases, uterine structural abnormalities and personal or family history of thrombosis. The control group consisted of 200 women who were matched for ethnic origin, with no spontaneous miscarriages and uncomplicated pregnancy (Table 1Go). Patients and controls were asked to fill in a questionnaire detailing their age, educational status, area of residence, number and pregnancy outcome, and risk factors for venous thromboembolism, including smoking and oral contraceptive use, and to sign an informed consent form indicating their acceptance to participate. The study was conducted after institutional ethics requirements were met. EDTA-anticoagulated blood (5 ml sample) was obtained from participants and was processed within 30 min of collection; plasma aliquots were then immediately frozen for tHcy measurements.


View this table:
[in this window]
[in a new window]
  		Table 1 Characteristics of study participants.
 
MTHFR genotyping
Total genomic DNA was isolated by the phenol–chloroform method, as is standard, and was dissolved in sterile nuclease-free water. MTHFR C677T genotype analysis was performed by PCR-RFLP analysis using HinfI (Frosst et al. 1995) and MboII (Friedman et al. 1999) digestion for C677T and A1298C detection respectively. The C677T mutation introduces a new HinfI restriction site, which results in the digestion of the 198 bp amplicon into 175 and 23 bp fragments. By abolishing an MboII restriction site, the A1298C mutation results in the digestion of the 163 bp amplicon into 84, 31, 30 and 18 bp fragments, while the wild-type variant is digested into 56, 31, 30, 28 and 18 bp fragments. Digested DNA fragments were then separated on a 3% agarose-1000 (Invitrogen, Paisley, UK) or 1% agarose-1000/2.5% NuSieve agarose (FMC Bioproducts, Rockland, ME, USA) prepared in 0.5 x TBE buffer for C677T and A1298C respectively.

Hcy level measurement
Blood was drawn from fasting subjects and placed in plain vaccutainers and tubes containing EDTA. For further analysis of plasma total Hcy, the sum of protein-bound and free Hcy was determined by ELISA using a commercial kit according to the manufacturer’s instructions (Diazyme Laboratories, San Diego, CA, USA). The assay sensitivity was 2.5–60.0 µM, and tHcy levels > 15 µM were considered elevated.

Statistical analysis
Data were expressed as percentages of the mean or as frequency of the allele. Allelic frequencies were calculated by a gene-counting method. Statistical analysis was performed on SPSS version 11.5 statistics software, which also computed the odd ratios (ORs) and 95% confidence intervals (95% CIs). Data were expressed as percentages of the mean or allele frequency; Pearson’s chi-square test was used to assess intergroup significance and Student’s t-test was used to determine differences in means. Regression multinomial logistic regression analysis was also determined, and results were expressed as beta and P values. Statistical significance was set at P < 0.05.


   Results
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
Discussion
 Acknowledgements
 References
 
Patients and controls
The demographics of study participants are summarized in Table 1Go. Patients and control subjects were of similar age (at first pregnancy; P = 0.434), body mass index (BMI.; P = 0.360), and residence/regional distribution (P = 0.531). Comparable numbers of smokers (P = 1.000), alcohol consumers (P = 1.000) and oral contraceptive users (P = 0.641) were seen in both groups. While the pregnancy rate was similar between patients and controls, the mean number of live births per woman was significantly higher among controls (P < 0.001), patients reporting 726 pregnancy losses in the first and second trimesters, compared with single-case pregnancy losses among controls, which were mainly induced/therapeutic (four in early, and seven in late pregnancy).

MTHFR C677T and A1298C genotype analysis
The distribution of MTHFR C677T and A1298C genotypes was in Hardy–Weinberg equilibrium among patients and controls. The frequency of MTHFR C677T mutant (‘T’) allele was significantly higher among patients than controls (P < 0.001) (Table 2Go). Higher frequencies of the C/T and the T/T (P < 0.001) genotypes of C677T SNP were seen in patients vs controls respectively (Table 2Go). Similarly, the frequency of the A1298C mutant (‘C’) allele was significantly higher among patients than controls (P < 0.001) (Table 2Go), and higher frequencies of the C/C but not the A/C genotypes of A1298C SNP were seen in patients vs controls respectively (Table 2Go), whereas a comparable frequency of double heterozygosity (677C/T and 1298A/C) was seen in 14 patients vs 5 control subjects (P = 0.10), and no double-homozygous case was seen in either group (Table 3Go).


View this table:
[in this window]
[in a new window]
  		Table 2 Distribution of MTHFR C677T and A1298C genotypes1.
 

View this table:
[in this window]
[in a new window]
  		Table 3 MTHFR C677T and A1298C genotype analysis.
 
Hcy proportion
Results in Table 4Go show that tHcy levels were comparable between patients and controls (P = 0.095; Table 4Go). Significantly elevated tHcy was noted in 677T/T carriers among patients and control subjects, as opposed to C/T or C/C genotype carriers. In contrast, tHcy levels were comparable among all A1298C genotype carriers, both in patients and in controls. Furthermore, the proportion of individuals with hyperhomocysteinemia was comparable between patients (27.7%) and controls (20.6%) (P = 0.249, OR = 1.477, 95% CI = 0.759–2.876).


View this table:
[in this window]
[in a new window]
  		Table 4 Homocysteine levels in patients and controls.
 
Distribution of MTHFR genotypes among patients
Increased prevalence of the MTHFR 677T/T genotype was seen in late (P < 0.05) and combined early-late (P < 0.001) abortions, but not in women with only early abortions (Table 5Go). Similarly, a higher proportion of the MTHFR 1298A/C genotype was seen in combined early-late abortions (P < 0.001), but not in women with only early or late abortions (Table 5Go). In addition, the prevalence of the heterozygous variant of MTHFR 677C/T (P < 0.05), but not 1298A/C, was seen only in combined early-late RPL (Table 5Go).


View this table:
[in this window]
[in a new window]
  		Table 5 Distribution of MTHFR genotypes among patients.
 
Risk factors for pregnancy loss
Predictors of early, late and early-late abortions were determined by performing three logistic regression analysis models with the dependent variable being early, late, and early-late RPL, and the independent potentially confounding variables being age (categorized according to a cut-off age of 35 years), smoking, Hcy levels, use of oral contraceptives, education, BMI and smoking (Table 6Go). The only variable that was selected using this technique for the first outcome (early RPL) was education (P = 0.005), whereas for the second outcome (late RPL) variables were education (P = 0.026) and homozygosity for C677T (P < 0.001), and for the third outcome (early-late), they were education (P = 0.004) and homozygosity for both C677T (P < 0.001) and A1298C (P = 0.026). Adjusting for the variables selected, Hcy levels was not associated with any of the stages of idiopathic RPL.


View this table:
[in this window]
[in a new window]
  		Table 6 Regression analysis.
 

   Discussion
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
Acknowledgements
 References
 
Insofar as they were implicated in pregnancy complications, including recurrent idiopathic RPLs (Nelen et al. 1997, Quere et al. 1998, Sarig et al. 2002), we investigated the association of MTHFR C677T and A1298C SNPs and hyperhomocysteinemia in women with idiopathic RPL. As patients and controls were matched for several risk factors (older age, smoking, obesity and use of oral contraceptives), results obtained showed that RPL patients had a higher prevalence of both MTHFR SNPs as compared with otherwise healthy control parous women. The allele frequency of MTHFR C677T and A1298C SNPs among control primigravid women was similar to that of healthy Tunisians (data not shown), thereby ruling out probability bias in control selection, and was comparable with rates established for European (Sacchi et al. 1997) and Mediterranean (Almawi et al. 2004a) communities. In view of their presence among control women, and as not all MTHFR C677T and A1298C mutant genotype carriers experienced RPLs, this indicated that the concerted participation of multiple inherited and non-inherited prothrombotic defects placed women at greatest risk.

Pregnancy losses were categorized into early (5–12 weeks), late (13–30 weeks) and combined early-late. The risk of pregnancy failure was significantly elevated only in carriers of the homozygous variant of both SNPs (677T/T and 1298C/C) and, interestingly, was seen in patients experiencing late (C677T) and combined early-late (C677T and A1298C), but not exclusively early miscarriages. This was in accord with earlier studies (Nelen et al. 1997, 1998, Lissak et al. 1999), which reported on the association of MTHFR 677T/T (acting through elevation of tHcy) with idiopathic RPL (Gris et al. 1999), more so with late than for first trimester abortions. Others failed to establish an association between MTHFR 677T/T genotype and idiopathic RPL (Kutteh et al. 1999, Carp et al. 2002), while others suggested that homozygosity for MTHFR C677T induced pregnancy loss only if present with other prothrombotic factors (Sarig et al. 2002).

Whereas hyperhomocysteinemia was notable among MTHFR 677T/T but not 1298C/C carriers in both groups, tHcy concentrations were comparable between patients and controls. It remains to be seen whether tHcy levels are indeed causally related to idiopathic pregnancy loss, with previous reports implicating hyperhomocysteinemia (Nelen et al. 2000a) and the Hcy-lowering agent folate (Nelen et al. 2000b) with RPL as risk factors for placental abruption or infarction, pre-eclampsia and early idiopathic RPL (Aubard et al. 2000, Steegers-Theunissen et al. 2004). While not tested here, it is possible that the association of the MTHFR 677T/T genotype with RPL, independently of hyperhomocysteinemia, was due to interference with red blood cell folate metabolism, as has been suggested (Alessio et al. 2004, Golbahar et al. 2005). Mechanistically, it was suggested that hyperhomocysteinemia precipitated thrombophilia by inducting the expression of tissue factor (TF), an initiator of blood coagulation in vivo (Fryer et al. 1993), by circulating monocytes, which apparently acted independently of peroxide and superoxides, since scavengers of both did not block the expression of Hcy-induced TF (Khajuria & Houston 2000). Hyperhomocysteinemia may also act by altering endothelial cell function through upregulation of the expression and secretion of monocyte chemoattractant protein-1 and interleukin-8, which by promoting leukocyte recruitment may contribute to the initiation and progression of vascular disease (Poddar et al. 2001).

While MTHFR C677T and A1298C SNPs were implicated in several pregnancy-related complications, including placental anomalies (Van der Molen et al. 2000), pre-eclampsia (Lachmeijer et al. 2001, Murakami et al. 2001) and RPL (Nelen et al. 1997, Quere et al. 1998 Sarig et al. 2002), the association of a particular mutation in diseased populations may be influenced by a number of environmental or genetic risk factors. Accordingly, the significance of the mutation may be overestimated. Regression analysis results clearly demonstrated that homozygosity for C677T was associated with late and combined early-late RPL, while homozygosity for A1298C was associated with combined early-late idiopathic RPL. Interestingly, education was the only non-inherited risk factor associated with RPL in the population examined. While explanation for this remains speculative, it is tempting to hypothesize that accompanying environmental factors related to maternal socio-economic status may influence RPL, as was suggested elsewhere (Manchester et al. 1995).

In conclusion, while MTHFR C677T and A1298C were more prevalent in women with idiopathic RPL, homozygosity for MTHFR C677T and A1298C were implicated in RPL after adjusting for inherited and non-inherited variables. It should be noted here that the contribution of inherited and environmental prothrombotic risk factors may vary significantly according to ethnicity. Further studies, including meta-analysis, are needed for a thorough understanding of the contribution of MTHFR mutations and hyperhomocysteinemia in idiopathic RPL.


   Acknowledgements
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
 Acknowledgements
References
 
The authors declare that there is no conflict of interest that would prejudice the impartiality of this scientific work.


   Footnotes
 
Received 12 May 2005
First decision 16 June 2005
Revised manuscript received 28 September 2005
Accepted 30 September 2005


   References
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
 Acknowledgements
 References
 

Alessio AC, Annichino-Bizzacchi JM, Bydlowski SP, Eberlin MN, Vellasco AP & Hoehr NF 2004 Polymorphisms in the methylenetetrahydrofolate reductase and methionine synthase reductase genes and homocysteine levels in Brazilian children. American Journal of Medical Genetics A 128 256–260.

Almawi WY, Ameen G, Tamim H, Finan RR & Irani-Hakime N 2004a Factor V G1691A, prothrombin G20210A, and methylenetetrahydrofolate reductase [MTHFR] C677T gene polymorphism in angiographically documented coronary artery disease. Journal of Thrombosis and Thrombolysis 17 199–205.[CrossRef][ISI][Medline]

Almawi WY, Finan RR, Tamim H, Daccache JL & Irani-Hakime N 2004b Differences in the frequency of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene among the Lebanese population. American Journal of Hematology 76 85–87.[CrossRef][ISI][Medline]

Aubard Y, Darodes N & Cantaloube M 2000 Hyperhomocysteinemia and pregnancy – review of our present understanding and therapeutic implications. European Journal of Obstetrics, Gynecology, and Reproductive Biology 93 157–165.[CrossRef][ISI][Medline]

Carp H, Salomon O, Seidman D, Dardik R, Rosenberg N & Inbal A 2002 Prevalence of genetic markers for thrombophilia in recurrent pregnancy loss. Human Reproduction 17 1633–1637.[Abstract/Free Full Text]

Chango A, Boisson F, Barbe F, Quilliot D, Droesch S, Pfister M, Fillon-Emery N, Lambert D, Fremont S, Rosenblatt DS & Nicolas JP 2000 The effect of 677C -> T and 1298A -> C mutations on plasma homocysteine and 5,10-methylenetetrahydrofolate reductase activity in healthy subjects. British Journal of Nutrition 83 593–596.

Chen M, Xia B, Rodriguez-Gueant RM, Bigard M & Gueant JL 2005 Genotypes 677TT and 677CT + 1298AC of methylenetetrahydrofolate reductase are associated with the severity of ulcerative colitis in central China. Gut 54 733–734.[Free Full Text]

Finan RR, Tamim H, Ameen G, Sharida HE, Rashid M & Almawi WY 2002 Prevalence of factor V G1691A (factor V-Leiden) and prothrombin G20210A gene mutations in a recurrent miscarriage population. American Journal of Hematology 71 300–305.

Foka ZJ, Lambropoulos AF, Saravelos H, Karas GB, Karavida A, Agorastos T, Zournatzi V, Makris PE, Bontis J & Kotsis A 2000 Factor V Leiden and prothrombin G20210A mutations, but not methylenetetrahydrofolate reductase C677T, are associated with recurrent miscarriages. Human Reproduction 15 458–462.

Friedman G, Goldschmidt N, Friedlander Y, Ben-Yehuda A, Selub J, Babaey S, Mendel M, Kidron M & Bar-On H 1999 A common mutation A1298C in human methylenetetrahydrofolate reductase gene: association with plasma total homocysteine and folate concentrations. Journal of Nutrition 129 1656–1661.

Friso S, Girelli D, Trabetti E, Stranieri C, Olivieri O, Tinazzi E, Martinelli N, Faccini G, Pignatti PF & Corrocher R 2002 A1298C methylenetetrahydrofolate reductase mutation and coronary artery disease: relationships with C677T polymorphism and homocysteine/folate metabolism. Clinical and Experimental Medicine 2 7–12.[CrossRef]

Frosst P, Blom HJ, Milos R, Goyette P, Sheppard CA, Matthews RG, Boers GJ, den Heijer M, Kluijtmans LA, van den Heuvel LP et al. 1995 A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase. Nature Genetics 10 111–113.[CrossRef][ISI][Medline]

Fryer RH, Wilson BD, Gubler DB, Fitzgerald LA & Rodgers GM 1993 Homocysteine, a risk factor for premature vascular disease and thrombosis, induces tissue factor activity in endothelial cells. Arteriosclerosis and Thrombosis 13 1327–1333.[Abstract/Free Full Text]

Golbahar J, Fathi Z & Tamadon M 2005 Distribution of 5,10-methylenetetrahydrofolate reductase (C667T) polymorphism and its association with red blood cell 5-methyltetrahydrofolate in the healthy Iranians. Clinical Nutrition 24 83–87.[CrossRef][ISI][Medline]

Graham IM, Daly LE, Refsum HM, Robinson K, Brattström LE, Ueland PM et al. 1997 Plasma homocysteine as a risk factor for vascular disease. The European Concerted Action Project. Journal of the American Medical Association 277 1775–1781.[Abstract]

Gris JC, Quere I, Monpeyroux F, Mercier E, Ripart-Neveu S, Tailland ML, Hoffet M, Berlan J, Daures JP & Mares P 1999 Case-control study of the frequency of thrombophilic disorders in couples with late foetal loss and no thrombotic antecedent – the Nimes Obstetricians and Haematologists Study5 (NOHA5). Thrombosis and Haemostasis 81 891–899.[ISI][Medline]

Hanson NQ, Aras O, Yang F & Tsai MY 2001 C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase gene: incidence and effect of combined genotypes on plasma fasting and post-methionine load homocysteine in vascular disease. Clinical Chemistry 47 661–666.

Holmes ZR, Regan L, Chilcott I & Cohen H 1999 The C677T MTHFR gene mutation is not predictive of risk for recurrent fetal loss. British Journal of Haematology 105 98–101.[CrossRef][ISI][Medline]

Jacques PF, Bostom AG, Williams RR, Ellison RC, Eckfeldt JH, Rosenberg IH, Selhub J & Rozen R 1996 Relation between folatestatus, a common mutation in methylenetetra-hydrofolate reductase, and plasmahomocysteine concentrations. Circulation 93 7–9.[Abstract/Free Full Text]

Khajuria A & Houston DS 2000 Induction of monocyte tissue factor expression by homocysteine: a possible mechanism for thrombosis. Blood 96 966–972.[Abstract/Free Full Text]

Kosmas IP, Tatsioni A & Ioannidis JP 2004 Association of C677T polymorphism in the methylenetetrahydrofolate reductase gene with hypertension in pregnancy and pre-eclampsia: a meta-analysis. Journal of Hypertension 22 1655–1662.[CrossRef][ISI][Medline]

Kutteh WH, Park VM & Deitcher SR 1999 Hypercoagulable state mutation analysis in white patients with early first-trimester recurrent pregnancy loss. Fertility and Sterility 71 1048–1053.[CrossRef][ISI][Medline]

Lachmeijer AM, Arngrimsson R, Bastiaans EJ, Pals G, ten Kate LP, de Vries JI, Kostense PJ, Aarnoudse JG & Dekker GA 2001 Mutations in the gene for methylenetetrahydrofolate reductase, homocysteine levels, and vitamin status in women with a history of preeclampsia. American Journal of Obstetrics and Gynecology 184 394–402.[CrossRef][ISI][Medline]

Lissak A, Sharon A, Fruchter O, Kassel A, Sanderovitz J & Abramovici H 1999 Polymorphism for mutation of cytosine to thymine at location 677 in the methylenetetrahydrofolate reductase gene is associated with recurrent early fetal loss. American Journal of Obstetrics and Gynecology 181 126–130.[CrossRef][ISI][Medline]

Makino A, Nakanishi T, Sugiura-Ogasawara M, Ozaki Y, Suzumori N & Suzumori K 2004 No association of C677T methylenetetrahydrofolate reductase and an endothelial nitric oxide synthase polymorphism with recurrent pregnancy loss. American Journal of Reproductive Immunology 52 60–66.[CrossRef]

Manchester DK, Nicklas JA, O’Neill JP, Lippert MJ, Grant SG, Langlois RG, Moore DH 3rd, Jensen RH, Albertini RJ & Bigbee WL 1995 Sensitivity of somatic mutations in human umbilical cord blood to maternal environments. Environmental and Molecular Mutagenesis 26 203–212.[CrossRef][ISI][Medline]

Murakami S, Matsubara N, Saitoh M, Miyakaw S, Shoji M & Kubo T 2001 The relation between plasma homocysteine concentration and methylenetetrahydrofolate reductase gene polymorphism in pregnant women. Journal of Obstetrics and Gynaecology Research 27 349–352.[ISI]

Nelen WL, Steegers EA, Eskes TK & Blom HJ 1997 Genetic risk factor for unexplained recurrent early pregnancy loss. Lancet 350 861.[ISI][Medline]

Nelen WL, Blom HJ, Thomas CM, Steegers EA, Boers GH & Eskes TK 1998 Methylenetetrahydrofolate reductase polymorphism affects the change in homocysteine and folate concentrations resulting from low dose folic acid supplementation in women with unexplained recurrent miscarriages. Journal of Nutrition 128 1336–1341.[Abstract/Free Full Text]

Nelen WL, Blom HJ, Steegers EA, den Heijer M & Eskes TK 2000a Hyperhomocysteinemia and recurrent early pregnancy loss: a meta-analysis. Fertility and Sterility 74 1196–1199.[CrossRef][ISI][Medline]

Nelen WL, Blom HJ, Steegers EA, den Heijer M, Thomas CM & Eskes TK 2000b Homocysteine and folate levels as risk factors for recurrent early pregnancy loss. Obstetrics and Gynaecology 95 519–524.

Poddar R, Sivasubramanian N, DiBello PM, Robinson K & Jacobsen DW 2001 Homocysteine induces expression and secretion of monocyte chemoattractant protein-1 and interleukin-8 in human aortic endothelial cells: implications for vascular disease. Circulation 103 2717–2723.[Abstract/Free Full Text]

Quere I, Bellet H, Hoffet M, Janbon C, Mares P & Gris JC 1998 A woman with five consecutive fetal deaths: case report and retrospective analysis of hyperhomocysteinemia prevalence in 100 consecutive women with recurrent miscarriages. Fertility and Sterility 69 152–154.[CrossRef][ISI][Medline]

Sacchi E, Tagliabue L, Duca F & Mannucci PM 1997 High frequency of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in Northern Italy. Thrombosis and Haemostasis 78 963–964.[ISI][Medline]

Sarig G, Younis JS, Hoffman R, Lanir N, Blumenfeld Z & Brenner B 2002 Thrombophilia is common in women with idiopathic pregnancy loss and is associated with late pregnancy wastage. Fertility and Sterility 77 342–347.[CrossRef][ISI][Medline]

Steegers-Theunissen RP, Van Iersel CA, Peer PG, Nelen WL & Steegers EA 2004 Hyper-homocysteinemia, pregnancy complications, and the timing of investigation. Obstetrics and Gynaecology 104 336–343.

Unfried G, Griesmacher A, Weismuller W, Nagele F, Huber JC & Tempfer CB 2002 The C677T polymorphism of the methylenetetrahydrofolate reductase gene and idiopathic recurrent miscarriage. Obstetrics and Gynaecology 99 614–619.

Van der Molen EF, Arends GE, Nelen WL, Van der Put NJ, Heil SG, Eskes TK & Blom HJ 2000 A common mutation in the 5,10-methylenetetrahydrofolate reductase gene as a new risk factor for placental vasculopathy. American Journal of Obstetrics and Gynecology 182 1258–1263.[CrossRef][ISI][Medline]

Van der Put NM, Gabreels F, Stevens EM, Smeitink JA, Trijbels FJ, Eskes TK, Van den Heuvel LP & Blom HJ 1998 A second common mutation in the methylenetetrahydrofolate reductase gene: an additional risk factor for neural-tube defects? American Journal of Human Genetics 62 1044–1051.[CrossRef][ISI][Medline]

Wang XP, Lin QD, Ma ZW & Zhao AM 2004 C677T and A1298C mutation of the methylenetetrahydrofolate reductase gene in unexplained recurrent spontaneous abortion. Zhonghua Fu Chan Ke Za Zhi 39 238–241.


This article has been cited by other articles:


Home page
 Int J EpidemiolHome page
M. Bochud, A. Chiolero, R. C Elston, and F. Paccaud
A cautionary note on the use of Mendelian randomization to infer causation in observational epidemiology
Int. J. Epidemiol., April 1, 2008; 37(2): 414 - 416.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Mtiraoui, N
Right arrow Articles by Mahjoub, T
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Mtiraoui, N
Right arrow Articles by Mahjoub, T

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS