Factor V Leiden and thermolabile methylenetetrahydrofolate reductase gene variants in an East Anglian preeclampsia cohort

Genetic variation in placental insufficiency: What have we learned over time?

Genetic variation shapes placental development and function, which has long been known to impact fetal growth and pregnancy outcomes such as miscarriage or maternal pre-eclampsia. Early epidemiology studies provided evidence of a strong heritable component to these conditions with both maternal and fetal-placental genetic factors contributing. Subsequently, cytogenetic studies of the placenta and the advent of prenatal diagnosis to detect chromosomal abnormalities provided direct evidence of the importance of spontaneously arising genetic variation in the placenta, such as trisomy and uniparental disomy, drawing inferences that remain relevant to this day. Candidate gene approaches highlighted the role of genetic variation in genes influencing immune interactions at the maternal-fetal interface and angiogenic factors. More recently, the emergence of molecular techniques and in particular high-throughput technologies such as Single-Nucleotide Polymorphism (SNP) arrays, has facilitated the discovery of copy number variation and study of SNP associations with conditions related to placental insufficiency. This review integrates past and more recent knowledge to provide important insights into the role of placental function on fetal and perinatal health, as well as into the mechanisms leading to genetic variation during development.

Interaction of thrombophilic SNPs in patients with unexplained infertility-multifactor dimensionality reduction (MDR) model analysis

PURPOSE

Our aim was to evaluate the frequency and SNP-SNP interactions between factor V Leiden (FVL) G1691A, prothrombin G20210A mutation, and C677T MTHFR and PAI-1 4G/5G gene polymorphisms in female IVF patients with unexplained infertility (UI) by using a multifactor dimensionality reduction (MDR) model analysis.

METHODS

A total of 225 subjects were enrolled in the study. There were 105 females in UI group and 120 healthy controls. Designated SNPs were determined by using allele-specific PCR methods. The difference in thrombophilia prevalence was assessed by a chi-square test and logistic regression analysis. Four-locus SNP interaction model was tested using the MDR approach. A ten-fold cross-validation consistency (CVC) and permutation testing were performed.

RESULTS

There was a significant difference of MTHFR C677T polymorphism frequency between the groups. Significantly less UI patients had MTHFR CC genotype (p = 0.005), while the risk allele T was more frequent (OR = 1.83, p = 0.0018). Logistic regression determined a significant association only for MTHFR C677T in our patients (TT genotype OR = 2.99). The MDR analysis confirmed the significance of a single-locus model for MTHFR C677T polymorphism (p = 0.015; OR = 2.93). However, the best, significant predictive model was the two-locus model comprising MTHFR C677T and FVL (CVC = 10/10, testing accuracy = 60.95%, p = 0.013; OR = 3.02).

CONCLUSION

The MTHFR C677T polymorphism was significantly associated with UI, with minor allele T being more frequent. Additionally, there was a significantly increased presence of MTHFR C677T with FVL mutation in these patients. Therefore, MTHFR and its interaction with FVL should be recognized as contributing factors in the pathogenesis of infertility.

Effects of factor v Leiden polymorphism on the pathogenesis and outcomes of preeclampsia

Background

Factor V Leiden polymorphism is a well-recognized genetic factor in the etiology of preeclampsia. Considering that Ghana is recording high incidence of preeclampsia, we examined if factor V Leiden is a contributory factor to its development and pregnancy outcomes.

Methods

STROBE consensus checklist was adopted to recruit eighty-one (81) consenting subjects after ethical clearance. Subjects were followed up till delivery to obtain outcomes of PE. Routine blood chemistry and proteinuria were done on all samples. Factor V Leiden was characterized by polymerase chain reaction and restriction fragment length polymorphism (RFLP). The data was captured as protected health information (PHI) and analyzed with SPSS version 22.

Results

Overall allelic frequencies found in FVL exon 10 were 0.67 and 0.33 for G and A alleles respectively. The FVL mutation was more in PE and hypertensive patients. Increased white blood cells, increased uric acid and a three – fold increment of AST / ALT ratio was observed in PE cases when stratified by FVL exons (exon 8 and 10). Significant differences were also observed between FVL and age, systolic blood pressure (SBP), diastolic blood pressure (DBP), liver enzymes, white blood cells (wbc), hemoglobin levels.

Conclusion

FVL mutation allele frequency was 0.33, a first report. The mutation was associated with increased uric acid, liver enzymes and blood cell indices suggestive of acute inflammation.

Association of hypertensive disorders of pregnancy risk and factor V Leiden mutation: A meta-analysis

AIM

To date, the conclusions of studies on a possible association between factor V Leiden (FVL, FV G1691A, rs6025) and hypertensive disorders of pregnancy (HDP) are conflicting. Here, we aimed to estimate the relationship between the risk of HDP and FVL.

METHODS

Eligible studies focused on FVL and HDP were searched from the PubMed and the Web of Science databases up to March 31, 2018. We used random effects model for the meta-analysis, and I² statistic to assess the degree of heterogeneity between all included studies. To evaluate the association between FVL and the risk of HDP, we calculated the odds ratio (OR) and 95% confidence intervals (CI) comparing cases and controls of all samples and each subgroup based on different regions.

RESULTS

Fifty citations on FVL and HDP were identified through the literature search, and a meta-analysis on the GA + AA genotype between 6041 cases and 8364 controls was conducted. The holistic analysis found that pregnant women with GA or AA genotype of FVL have a 1.97-fold (95% CI: 1.64-2.35, P < 0.00001) increased risk of HDP compared with GG carriers. While the OR are 2.23 (95% CI: 1.76-2.84, P < 0.00001) and 1.90 (95% CI: 1.12-3.23, P = 0.02) in Europe and the Middle East subgroups, respectively.

CONCLUSION

Factor V Leiden mutation is associated with an increased risk of HDP, and is particularly associated with preeclampsia and eclampsia in European women. However, further high-quality studies are warranted to confirm the possible effectiveness of FVL in HDP patients.

Physiopathology of human embryonic implantation: clinical incidences

Embryo implantation consists of a series of events promoting the invasion of the endometrium and then the uterine arterial system by the extra-embryonic trophoblast. In order for this semi-heterologous implantation to succeed, the endometrium has to first undergo a number of structural and biochemical changes (decidualization). The decidua's various constituents subsequently play a role in the embryonic implantation. The third step is the transformation of the uterine vascular system and the growth of the placenta, which will provide the foetoplacental unit with nutrients. Several physiopathological aspects will be discussed: 1) the implantation window, regulated by maternal and embryonic hormonal secretions and thus influenced by any defects in the latter: dysharmonic luteal phase, 21-hydroxylase block, abnormal integrin expression, 2) the successive trophoblast invasions of uterine vessels which, when defective, lead to early embryo loss or late-onset vascular pathologies, as preeclampsia, 3) the pregnancy's immunological equilibrium, with a spontaneously tolerated semi-allogeneic implant, 4) the impact of pro-coagulant factors (thrombophilia) on the pregnancy's progression, 5) the environment of the uterus, ranging from hydrosalpinx to uterine contractions. In summary, the least anatomical or physiological perturbation can interfere with human embryonic implantation - a very particular phenomenon and a true biological paradox.

Associations between phenotypes of preeclampsia and thrombophilia

OBJECTIVES

Preeclampsia complicates 2-8% of all pregnancies. Studies on the association of preeclampsia with thrombophilia are conflicting. Clinical heterogeneity of the disease may be one of the explanations. The present study addresses the question whether different phenotypes of preeclampsia are associated with thrombophilia factors. Study design We planned a retrospective cohort study. From 1985 until 2010 women with preeclampsia were offered postpartum screening for the following thrombophilia factors: anti-phospholipid antibodies, APC-resistance, protein C deficiency and protein S deficiency, hyperhomocysteineamia, factor V Leiden and Prothrombin gene mutation. Hospital records were used to obtain information on phenotypes of the preeclampsia and placental histology.

RESULTS

We identified 844 women with singleton pregnancies who were screened for thrombophilia factors. HELLP complicated 49% of pregnancies; Fetal growth restriction complicated 61% of pregnancies. Early delivery (<34th week) occurred in 71% of pregnancies. Any thrombophilia factor was present in 29% of the women. Severe preeclampsia was associated with protein S deficiency (p=0.01). Fetal growth restriction was associated with anti-phospholipid antibodies (p<0.01). Early onset preeclampsia was associated with anti-phospholipid antibodies (p=0.01). Extensive placental infarction (>10%) was associated with anti-phospholipid antibodies (p<0.01). Low placental weight (<5th percentile) was associated with hyperhomocysteineamia (p=0.03). No other associations were observed.

CONCLUSIONS

Early onset preeclampsia, especially if complicated by fetal growth restriction, are associated with anti-phospholipid antibodies. Other phenotypes of preeclampsia, especially HELLP syndrome, were not associated with thrombophilia. We advise only to test for anti-phospholipid antibodies after early onset preeclampsia, especially if complicated by fetal growth restriction. We suggest enough evidence is presented to justify no further studies are needed.

Folate metabolism gene polymorphisms MTHFR C677T and A1298C and risk for preeclampsia: a meta-analysis

OBJECTIVES

MTHFR C677T and A1298C have been associated with the risk of preeclampsia (PE), but with conflicting results. We performed this meta-analysis to derive a more precise estimation of the association between MTHFR polymorphisms and PE.

STUDY DESIGN

An electronic search of PubMed and Chinese Biomedicine database was conducted to select studies for meta-analysis. 54 case controlled studies containing MTHFR C677T and A1298C gene polymorphisms were chosen, and odds ratio (OR) with confidence interval (CI) was used to assess the strength of this association.

RESULT

These studies evaluated 7398 cases and 11230 controls for MTHFR C677T. The overall results suggested that MTHFR C677T was associated with the risk of PE. (T vs. C: OR = 1.157, 95% CI: 1.057-1.266, p = 0.002; TT + CT vs. CC: OR = 1.165, 95% CI : 1.049-1.293, P = 0.004; TT vs. CT + CC: OR = 1.371, 95% CI: 1.153-1.63, p < 0.001). We also evaluated 1103 cases and 988 controls for MTHFR A1298C but could not demonstrate an increased risk of PE for this polymorphism (p = 0.667). A symmetric funnel plot, the Egger's test (p = 0.819) suggested a lack of publication bias.

CONCLUSION

This meta-analysis supports the idea that MTHFR C677T genotype is associated with increased risk for PE, especially in the case of Asians and Caucasians.

Association between thrombophilia gene polymorphisms and preeclampsia: a meta-analysis

OBJECTIVE

To estimate the relationship between the risk of preeclampsia and two thrombophilia gene single-nucleotide polymorphisms (SNPs), the factor V G1691A SNP and the prothrombin G20210A SNP.

DATE SOURCES

A systematic search of the English-language literature up to November 2012 was performed using Medline and EMBASE. Search terms included "preeclampsia," "thrombophilia," "factor V Leiden," "prothrombin gene 20210," and their combinations.

RESULT(S)

Thirty-seven studies with 5048 preeclampsia patients and 6796 controls were included in the meta-analysis. We found that the prothrombin G20210A polymorphism was associated with an increased risk of all preeclampsia (pooled odds ratio (OR) = 1.81, 95% confidence interval (CI) 1.25-2.63) and severe preeclampsia (pooled OR = 3.02, 95%CI 2.06-4.45). Meanwhile, the pooled OR for the association between factor V Leiden and all preeclampsia was 1.60 (95%CI 1.28-2.00) and 2.45 (95%CI 1.63-3.69) for the cases of severe preeclampsia.

CONCLUSION(S)

This meta-analysis supports that the factor V G1691A SNP and the prothrombin G20210A SNP are associated with an increased risk for both preeclampsia overall and severe preeclampsia.

Associations of MTHFR gene polymorphisms with hypertension and hypertension in pregnancy: a meta-analysis from 114 studies with 15411 cases and 21970 controls

BACKGROUND

Several epidemiological studies have investigated the associations of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with hypertension (H) or hypertension in pregnancy (HIP). However, the results were controversial. We therefore performed a comprehensive meta-analysis to provide empirical evidences on the associations.

METHODOLOGIES

The English and Chinese databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, sensitivity analysis, cumulative meta-analysis and assessment of publication bias were performed in our study.

PRINCIPAL FINDINGS

A total of 114 studies with 15411 cases and 21970 controls were included, 111 studies with 15094 cases and 21633 controls for the C677T polymorphism and 21 with 2533 cases and 2976 controls for the A1298C polymorphism. Overall, the C677T polymorphism was significantly associated with H and HIP (H & HIP: OR = 1.26, 95% CI = 1.17-1.34; H: OR = 1.36, 95% CI = 1.20-1.53; HIP: OR = 1.21, 95% CI = 1.08-1.32). Stratified analysis by ethnicity revealed a significant association among East Asians and Caucasians, but not among Latinos, Black Africans, and Indians and Sri Lankans. In the stratified analyses according to source of controls, genotyping method, sample size and study quality, significant associations were observed in all the subgroups, with the exception of population based subgroup in H studies and large sample size and "others" genotyping method subgroups in HIP studies. For the A1298C polymorphism, no significant association was observed either in overall or subgroup analysis under all genetic models.

CONCLUSIONS

This meta-analysis suggests that the MTHFR C677T rather than A1298C polymorphism may be associated with H & HIP, especially among East Asians and Caucasians.

Methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism and risk of preeclampsia: an updated meta-analysis based on 51 studies

BACKGROUND AND AIMS

The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been considered to be associated with preeclampsia (PE), but the results from previous studies were conflicting. The present study aimed at investigating the frequency of preeclampsia according to the distribution polymorphism using a meta-analysis on the published studies.

METHODS

The English and Chinese databases were searched to identify eligible studies published in English before August 2012. Data were extracted using standardized methods. The association was assessed by odds ratio (OR) with 95% confidence intervals (CI). Begg's test was used to measure publication bias.

RESULTS

A total of 51 case-control studies containing 6,403 patients and 11,346 controls were involved in this meta-analysis. Significant associations were detected between MTHFR C677T polymorphism and risk of PE in the overall population for TT vs. CC (OR = 1.280, 95% CI: 1.074-1.525), recessive model (OR = 1.264, 95% CI: 1.067-1.303), and dominant genetic model (OR = 1.174, 95% CI: 1.057-1.303); in Caucasian population for dominant model (OR = 1.136, 95% CI: 1.022-1.263), and in East Asia population for TT vs. CC (OR = 2.199, 95% CI: 1.366-3.924) CT vs. CC (OR = 1.453, 95% CI: 1.001-2.109), recessive model (OR = 1.742, 95% CI: 1.202-2.525), and dominant model (OR = 1.783, 95% CI: 1.271-2.501). Conversely, no associations were detected in Latin America, South Asia, and Africa populations.

CONCLUSIONS

Results of the meta-analysis suggest that the MTHFR C677T polymorphism was associated with risk of PE in overall, Caucasian, and East Asia populations. Nevertheless, the results for Latino, East Asians, South Asians and Africans should be interpreted with caution due to the small sample size.

Factor V Leiden mutation and its impact on pregnancy complications

OBJECTIVE

The aim of this prospective study was to find the association between the factor V Leiden mutation and adverse pregnancy outcomes.

METHODS

This study is an analysis of a prospective observational study of the frequency of placenta-mediated complications of factor V Leiden mutation carriers. We compared pregnancy outcomes of 11 women with a heterozygous form of the factor V Leiden mutation with 41 women of a control group.

RESULTS

All pregnancies ended with delivery of a living infant. None of the 52 pregnancies were complicated by venous thromboembolism. There were a few significant differences regarding placenta-mediated complications. The gestational age at delivery showed small significant differences. There was a significant difference in the birth weight deviation in percentage between FVL carriers and controls. The incidence of blood loss exceeding 1000 ml was higher in the control group.

CONCLUSIONS

Carriership of the factor V Leiden mutation did not affect the incidence of preeclampsia. Adverse pregnancy outcomes such as placental abruption were rare. Eclampsia, intrauterine fetal death and venous thromboembolism did not occur. Our results provide evidence that the maternal heterozygous FVL mutation did not increase the risk of an adverse pregnancy outcome.

Factor V Leiden mutation and pregnancy-related complications

OBJECTIVE

The objective of the study was to determine the prevalence of the factor V Leiden (FVL) mutation and its association with obstetric complications, blood loss during delivery, and venous thromboembolism (VTE).

STUDY DESIGN

This was a prospective, observational, case-cohort study of 491 FVL carriers and 1055 controls derived from 6003 screened women. Data were analyzed with a Student t test and cross-tabulation.

RESULTS

FVL carriership prevalence was 8.3%. Gestational age at delivery, birthweight deviation, gestational hypertension, and preeclampsia incidences did not differ between groups. The incidences of placental abruption, neonatal asphyxia, eclampsia, intrauterine fetal death, intrapartum death, and unexplained late miscarriage were low. The incidence of major blood loss at delivery was lower in carriers. There were 3 VTEs among carriers and none among controls.

CONCLUSION

FVL carriership did not influence pregnancy-induced hypertension, birthweight, or prematurity but raised the risk of venous thromboembolism and lowered the risk of major blood loss.

The origin of Eastern European Jews revealed by autosomal, sex chromosomal and mtDNA polymorphisms

Background

This study aims to establish the likely origin of EEJ (Eastern European Jews) by genetic distance analysis of autosomal markers and haplogroups on the X and Y chromosomes and mtDNA.

Results

According to the autosomal polymorphisms the investigated Jewish populations do not share a common origin, and EEJ are closer to Italians in particular and to Europeans in general than to the other Jewish populations. The similarity of EEJ to Italians and Europeans is also supported by the X chromosomal haplogroups. In contrast according to the Y-chromosomal haplogroups EEJ are closest to the non-Jewish populations of the Eastern Mediterranean. MtDNA shows a mixed pattern, but overall EEJ are more distant from most populations and hold a marginal rather than a central position. The autosomal genetic distance matrix has a very high correlation (0.789) with geography, whereas the X-chromosomal, Y-chromosomal and mtDNA matrices have a lower correlation (0.540, 0.395 and 0.641 respectively).

Conclusions

The close genetic resemblance to Italians accords with the historical presumption that Ashkenazi Jews started their migrations across Europe in Italy and with historical evidence that conversion to Judaism was common in ancient Rome. The reasons for the discrepancy between the biparental markers and the uniparental markers are discussed.

Reviewers

This article was reviewed by Damian Labuda (nominated by Jerzy Jurka), Kateryna Makova and Qasim Ayub (nominated by Dan Graur).

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

Single inherited thrombophilias and adverse pregnancy outcomes

INTRODUCTION

Inherited thrombophilia is believed to be a multiple gene disease with more than one defect. We aimed to determine the association between single thrombophilic patterns and a variety of pregnancy diseases.

METHODS

284 pregnant women were recruited for the present study and were divided in two groups: A group (176 controls) and B group (108 cases). Patients belonging to the B group had one of the following: severe pre-eclampsia, hemolysis, hepatic enzymes increase, hypertension and low platelet count (HELLP) syndrome, gestational hypertension, fetal growth restriction, intrauterine death, abruptio placentae and disseminated intravascular coagulopathy. To detect methylenetetrahydrofolate reductase (MTHFR) A1298C, MTHFR C677T, factor V Leiden, PAI-1, mutant prothrombin G20210A, an inverse hybridization technology was used. Plasma homocysteine, antithrombin (AT) III and protein S were determined. A modified functional activated protein C resistance was detected.

RESULTS

MTHFR C677T and hyperhomocysteinemia were more prevalent than other thrombophilias. Deficiency in AT III was significantly linked with pre-eclampsia (relative risk 0.88; 95% CI 0.83-0.94). Activated protein C resistance (APCR) was significantly related to the abruptio placentae (relative risk 0.71; 95% CI 0.61-0.82).

COMMENTS

Apart from the linkage between AT III deficiency and the occurrence of pre-eclampsia, and apart from the increased risk of abruptio placentae in pregnant women with altered APCR, we obtained findings in contrast with some of the published literature. In our case series, no association of pre-eclampsia with factor V Leiden or with prothrombin gene mutation was found.

High frequency of methylenetetrahydrofolate reductase 677TT genotype in Hungarian HELLP syndrome patients determined by quantitative real-time PCR

Our aim was to determine the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in hypertensive disorders during pregnancy. We conducted our experiments on isolated DNA samples of 73 healthy pregnant, 101 severe pre-eclamptic and 63 HELLP syndrome women in this study. The MTHFR C677T polymorphism was determined by quantitative real-time PCR method. A significantly higher number of the TT genotype (25.4%) was found in the HELLP syndrome group compared to the healthy (8.2%) and severe pre-eclamptics group (8.9%) (P=0.03). The frequency of the mutant T allele was found to be 45.2% of HELLP syndrome, whereas it was 32.2% of the healthy pregnant (P=0.03) and 30.2% (P=0.008) of the severe pre-eclamptic patients. In the HELLP group a high frequency of eclampsia was observed (12.6%) and among them 75% had the MTHFR C677T mutation.

Racial disparity in hypertensive disorders of pregnancy in New York State: a 10-year longitudinal population-based study

OBJECTIVES

We studied trends of hypertensive disorders of pregnancy by residential socioeconomic status (SES) and racial/ethnic subgroups in New York State over a 10-year period.

METHODS

We merged New York State discharge data for 2.5 million women hospitalized with delivery from 1993 through 2002 with 2000 US Census data.

RESULTS

Rates of diagnoses for all hypertensive disorders combined and for preeclampsia individually were highest among Black women across all regions and neighborhood poverty levels. Although hospitalization rates for preeclampsia decreased over time for most groups, differences in rates between White and Black women increased over the 10-year period. The proportion of women living in poor areas remained relatively constant over the same period. Black and Hispanic women were more likely than White women to have a form of diabetes and were at higher risk of preeclampsia; preeclampsia rates were higher in these groups both with and without diabetes than in corresponding groups of White women.

CONCLUSIONS

An increasing trend of racial/ethnic disparity in maternal hypertension rates occurred in New York State during the past decade. This trend was persistent after stratification according to SES and other risk factors. Additional research is needed to understand the factors contributing to this growing disparity.

Searching for genetic clues to the causes of pre-eclampsia

Pre-eclampsia and its related syndromes are significant causes of maternal and fetal death, but much remains unclear about the underlying disease mechanisms. Epidemiological research has consistently demonstrated a familial predisposition to pre-eclampsia, which has encouraged genetic research in this area. The goal is the discovery of susceptibility genes which will inform understanding of the pathophysiology of pre-eclampsia, and may prove to be targets for therapeutic or preventative strategies. This review examines the application of molecular technologies to the search for genetic clues in pre-eclampsia and emphasizes the importance of integrative approaches. The results of recent genome-wide linkage studies have been particularly encouraging, identifying a number of loci which merit closer examination. Candidate gene studies have proved less fruitful, generating conflicting and inconclusive results. Possible explanations and remedies for this deficiency are discussed with a view to stimulating closer collaboration between researchers in this field.

The relationship between thrombophilic mutations and preeclampsia: a prospective case-control study

BACKGROUND

Preeclampsia and its association with thrombophilia remain controversial, due to inconsistent results in different studies, which include different ethnic groups, selection criteria, and patient numbers. The aim of this study was to determine the relationship between thrombophilia and preeclamptic patients in our region.

METHODS

In a prospective case-control study, we compared 100 consecutive women with preeclampsia and eclampsia (group 1) with 100 normal pregnant women (group 2). All women were tested two months after delivery for mutations of factor V Leiden, methylenetetrahydrofolate reductase (MTHFR), and prothrombin gene mutation as well as for deficiencies of protein C, protein S, and antithrombin III.

RESULTS

A thrombophilic mutation was found in 42 (42%) and 28 (28%) women in group 1 and group 2, respectively (P=0.27, OR 1.5, 95%CI 1.0-2.2). The incidence of Factor V Leiden mutation (heterozygous), prothrombin mutation (heterozygous), prothrombin mutation (homozygous), MTHFR mutation (homozygous) was not statistically significant in group 1 compared with group 2 (P>0.05). Also, deficiencies of protein S, protein C, and antithrombin III were not statistically significant in group 1 compared with group 2 (P>0.05).

CONCLUSION

There was no difference in thrombophilic mutations between preeclamptic patients and normal pregnant women in our region. Therefore, we suggest that preeclamptic patients should not be tested for thrombophilia.

Thrombophilia in pregnancy: a systematic review

Growing evidence suggests that thrombophilia is associated with venous thromboembolism (VTE) and adverse pregnancy outcomes. However, methodological limitations have made it difficult to obtain a clear overview of the overall risks. We conducted a systematic review to determine the risk of VTE and adverse pregnancy outcomes associated with thrombophilia in pregnancy. The effectiveness of prophylactic interventions during pregnancy was also evaluated. Major electronic databases were searched, relevant data abstracted and study quality assessed by two independent reviewers. Odds ratios (ORs) stratified by thrombophilia type were calculated for each outcome. A total of 79 studies were included in our review. The risks for individual thrombophilic defects were determined for VTE (ORs, 0.74-34.40); early pregnancy loss (ORs, 1.40-6.25); late pregnancy loss (ORs, 1.31-20.09); pre-eclampsia (ORs, 1.37-3.49); placental abruption (ORs, 1.42-7.71) and intrauterine growth restriction (ORs, 1.24-2.92). Low-dose aspirin plus heparin was the most effective in preventing pregnancy loss in thrombophilic women (OR, 1.62). Our findings confirm that women with thrombophilia are at risk of developing VTE and complications in pregnancy. However, despite the increase in relative risk, the absolute risk of VTE and adverse outcomes remains low. There is also a lack of controlled trials of antithrombotic intervention to prevent pregnancy complications. Thus, at present, universal screening for thrombophilia in pregnancy cannot be justified clinically.

Mechanisms of Disease: pre-eclampsia

Pre-eclampsia, a syndrome of pregnant women, is one of the leading causes of maternal and fetal morbidity and mortality. Despite active research, the etiology of this disorder remains an enigma. Recent work has, however, provided promising explanations for the causation of the disorder and some of its phenotypes. Evidence indicates that the symptoms of hypertension and proteinuria, upon which the diagnosis of pre-eclampsia is based, have several underlying causes. Nevertheless, the treatment of pre-eclampsia has not changed significantly in over 50 years. This review describes the most recent insights into the pathophysiology of pre-eclampsia from both basic and clinical research, and attempts to provide a unifying hypothesis to reconcile the abnormalities at the feto-placental level and the clinical features of the maternal syndrome. The novel findings outlined in this review provide a rationale for potential future prophylactic and therapeutic interventions for pre-eclampsia.

Methylenetetrahydrofolate Reductase Polymorphisms and the Risk of Gestational Hypertension

BACKGROUND

Evidence on the association of 5,10 methylentetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms in women with gestational hypertension is inconsistent. It is also unknown whether the fetal genotype is relevant, or whether folic acid supplementation modifies this association.

METHODS

The study population was composed of U.S. and Canadian white women with nonmalformed infants participating in the Slone Epidemiology Center Birth Defects Study between 1993 and 2000. Women were interviewed within 6 months after delivery regarding multivitamin use in pregnancy and the occurrence of gestational hypertension, among other factors. DNA was extracted from cheek swabs and gene alleles determined by restriction fragment length polymorphism analysis. We compared the prevalence of the 677TT/CT and 1298CC/AC genotypes between cases with gestational hypertension (54 mothers and their 51 offspring) and controls (100 mothers and their 99 offspring). We also estimated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression to control for geographic region and calendar year.

RESULTS

The T allele was present in 69% of women with gestational hypertension versus 57% of control women (compared with 677CC, OR = 1.9; 95% CI = 0.9-4.0). The offspring of case and control women had a 677TT/CT genotype prevalence of 68% and 47%, respectively (2.4; 1.1-5.0). Among women supplemented with folic acid during the first 5 months of pregnancy, the ORs for maternal and fetal 677TT/CT genotypes were 0.9 (0.3-2.5) and 2.1 (0.7-6.0), respectively. Neither maternal nor fetal 1298CC/AC genotypes were associated with an increased risk of gestational hypertension.

CONCLUSION

Maternal and fetal MTHFR C677T polymorphism may be associated with a moderately increased risk of gestational hypertension, and there is a suggestion that this association may be diminished among women receiving folate supplementation during pregnancy.

Preeclampsia: a renal perspective

Preeclampsia is a syndrome that affects 5% of all pregnancies, producing substantial maternal and perinatal morbidity and mortality. The aim of this review is to summarize our current understanding of the pathogenesis of preeclampsia with special emphasis on the recent discovery that circulating anti-angiogenic proteins of placental origin may play an important role in the pathogenesis of proteinuria and hypertension of preeclampsia.

Thrombophilia and pregnancy outcomes

Pregnancy complications are still a challenge for physicians, because knowledge of pathomechanisms and prophylactic measures is still limited. In recent years thrombophilia as a risk factor for pregnancy complications has gained much attention in the scientific community. However, data on this topic in the literature are conflicting. Besides an established association between antiphospholipid antibodies and pregnancy loss, available data suggest additional associations for antithrombin deficiency, hyperhomocysteinemia and also for factor (F)V Leiden, prothrombin G20210A variation, and protein S-deficiency. The contribution of thrombophilia to the risk of pre-eclampsia is less well established and recent studies did not confirm earlier data suggesting an association between thrombophilia and pre-eclampsia. A limited number of prospective studies have failed to reveal an increased risk of pregnancy complications in unselected women with thrombosis risk factors. Low-molecular weight heparin (LMWH) seems to have a positive effect on pregnancy outcome after single or recurrent abortions, however, data from only one controlled trial are available. Experience in the prevention of pre-eclampsia by prophylactic heparin is very limited, and in addition, data on pregnancy complications in women with known heritable thrombophilia or a history of thrombosis are inconsistent. These women will usually have a favorable pregnancy outcome referring to the European Prospective Cohort on Thrombophilia Study. In conclusion, thrombophilia screening might be justified in women with pregnancy loss and treatment with LMWH might be considered in those with pregnancy loss and thrombophilia. Further prospective studies and controlled interventional trials are urgently needed.

Association of C677T polymorphism in the methylenetetrahydrofolate reductase gene with hypertension in pregnancy and pre-eclampsia: a meta-analysis

OBJECTIVE

To evaluate whether the C677T polymorphism of the methylenetetrahydofolate reductase (MTHFR) gene is consistently associated with hypertension in pregnancy.

DESIGN

Meta-analysis of studies comparing women with and without hypertension in pregnancy for the C677T MTHFR polymorphism.

METHODS

Studies were identified with MEDLINE and EMBASE searches complemented with perusal of bibliographies of retrieved articles and communication with investigators. Between-study heterogeneity was estimated and data were combined with random effects models. Sensitivity analyses examined the effect of population and disease characteristics. Bias diagnostics evaluated the evolution of the postulated genetic effect over time and the potential for publication bias.

RESULTS

Across 23 comparisons (3169 hypertensive women, 3044 controls), having the T allele (TT or CT) increased the odds of hypertensive disease of pregnancy by 1.21-fold (95% confidence interval, 1.01-1.44), but there was large between-study heterogeneity (P = 0.003). The results were similar and heterogeneity persisted when sensitivity analyses were limited to studies of Caucasian populations, or those of patients with significant proteinuria. While patients with diastolic hypertension > or = 110 mmHg showed an odds ratio of 1.41 (95% confidence interval, 1.03-1.73), no association was seen in patients with less severe diastolic hypertension (odds ratio, 1.00; 95% confidence interval, 0.61-1.65). Early published studies tended to show stronger associations than the subsequent studies.

CONCLUSIONS

While bias cannot be excluded, the meta-analysis suggests that the T allele may increase the risk of severe diastolic hypertension during pregnancy.

Genetic thrombophilias and preeclampsia: a meta-analysis

OBJECTIVE

To assess the relationship between the factor V Leiden (1691 G-A) single nucleotide polymorphism (SNP), the methylene tetrahydrofolate reductase (MTHFR) 677 C-T SNP, and the prothrombin 20210 G-A SNP and the risk of preeclampsia, by conducting a meta-analysis of all case-control studies with data on these polymorphisms and the risk of preeclampsia.

DATA SOURCES

MEDLINE (1966 to November 2002), EMBASE (1980 to November 2002). Search terms included "preeclampsia," "thrombophilia," "factor V Leiden," "protein C," "MTHFR," "methylenetetrahydrofolate reductase," "homocysteine," and "prothrombin gene 20210."

METHODS OF STUDY SELECTION

Case-control studies of genetic thrombophilias and preeclampsia were included.

TABULATION, INTEGRATION, AND RESULTS

We identified 349 titles and reviewed 47 articles for inclusion and exclusion criteria. Thirty-one studies with 7,522 patients were included in the meta-analysis. Data from patients characterized as having severe preeclampsia were extracted and analyzed separately. The pooled odds ratio (OR) for the association of factor V Leiden and all cases of preeclampsia was 1.81 (95% confidence interval [CI] 1.14-2.87) and 2.24 (95% CI 1.28-3.94) for cases of severe preeclampsia. The pooled OR for the MTHFR 677 TT genotype and all preeclampsia was 1.01 (95% CI 0.79-1.29) and 1.38 (95% CI 0.93-2.06) for severe preeclampsia. The OR for the prothrombin 20210 polymorphism and all preeclampsia was 1.37 (95% CI 0.72-2.57) and 1.98 (.94-4.17) for severe preeclampsia.

CONCLUSION

This meta-analysis suggests that the factor V Leiden SNP is associated with an increased risk of preeclampsia. Further studies are warranted to determine whether subgroups of high-risk women should be screened for this mutation.

Genetic thrombophilias and uterine artery Doppler velocimetry and preeclampsia

OBJECTIVE

The aim of this study was to evaluate the correlation between genetic thrombophilic mutations, uterine artery Doppler at 24 weeks of gestation and preeclampsia.

METHODS

In a case control study we performed the genetic analysis for Leiden mutation of factor V gene (FV), G20210A mutation of the prothrombin gene (PT) and C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene in 103 women that had already attended routine ultrasonography scanner at 20 weeks at our Department.

RESULTS

The frequency of heterozygous carriers of the factor V Leiden was 17.4% in the women with preeclampsia and abnormal artery Doppler compared with 3.12% in the patients with normal pregnancies. This difference was statistically significant (P<0.05). The frequency of mutation G20210A of prothrombin gene was 1.5 vs. 4.3% between women with normal pregnancies and with preeclampsia. This difference is not statistically significant. The frequency of homozygous patients for the C677T mutation of MTHFR gene among the patients with preeclampsia was 21.7% and in the control group was 10.3%, but this difference is not statistically significant. No thrombophilic gene variants were found in women with preeclampsia and normal uterine artery Doppler.

CONCLUSION

We demonstrated the important association between factor V Leiden mutation, abnormal uterine Doppler at 24 weeks and preeclampsia in our population.

Genetic thrombophilia has pleiotropic effects in pregnancy

Genetic thrombophilia has been established as a risk factor for pregnancy-associated disorders, such as thrombosis, early and late miscarriage, and pre-eclampsia. Associations between the factor V (F5) Leiden G1691A and the prothrombin/factor II (F2) G20210A SNPs and pre-eclampsia have been evaluated in over 50 association studies. A pooled analysis of 23 and 11 studies demonstrates that carriage of the F5 Leiden G1691A (p < 0.001; odds ratio [OR] 2.0; 95% confidence interval [CI] 1.6-2.5) and the F2 G20210A (p < 0.001; OR 1.8; 95% CI 1.1-2.9) SNPs is significantly associated with pre-eclampsia. Besides pre-eclampsia, genotyping for the F5 Leiden G1691A and the F2 G20210A SNPs is also useful for individual risk assessment regarding pregnancy-associated thrombosis. Carriers of the F5 Leiden G1691A SNP will develop this condition in 6.4% of heterozygotes and in 8.9-16.7% of homozygotes. A total of 6.2% of women with the F2 G20210A SNP and 17.8% of women with simultaneous carriage of the F5 Leiden G1691A and F2 G20210A SNPs will develop pregnancy-associated thrombosis. Both the F5 Leiden G1691A and F2 G20210A SNPs are also risk factors of early recurrent, late recurrent and late spontaneous miscarriage based on a published meta-analysis of 31 studies. These women may benefit from prophylactic heparinization. Six case-control and cohort studies of 687 women with genetic thrombophilia document live birth rates of 82% (181/221) using low-molecular-weight heparin or fractionated heparin compared with 20% (95/466) without therapy (p < 0.001, OR 17.7; 95% CI 12.2-25.5). Based on the data in the literature, including association studies and meta-analyses of these association studies, it can be concluded that genetic thrombophilia due to carriage of the F5 Leiden G1691A and F2 G20210A SNPs is a significant and clinically relevant risk factor for pre-eclampsia, pregnancy-associated thrombosis, and early and late miscarriages.

Pathophysiology of preeclampsia: links with implantation disorders

The phenomenon of implantation anchors the embryo into the uterine wall and produces a hemochorial placenta that maintains the pregnancy and fetal growth. Implantation and placentation are intimately linked and cannot be dissociated either in time or in space. Preeclampsia is characterized by hypertension and proteinuria. It is secondary to an anomaly of the invasion of the uterine spiral arteries by extra-villous cytotrophoblast cells, associated with local disruptions of vascular tone, of immunological balance and inflammatory status, and sometimes with genetic predispositions. Preeclampsia is a disease of early pregnancy, a form of incomplete spontaneous abortion, but is expressed late in pregnancy. Aspirin may play a favorable role in implantation which is related to the genesis of preeclampsia and some cases of intra-uterine growth restriction. The most important points in obtaining a preventive effect from low-dose aspirin during the pregnancy are early treatment (before 13 weeks of gestation) and the prescription of a sufficient dose (more than 100 mg per day).

Thrombophilia and pregnancy complications

OBJECTIVE

This systematic review examines the strength of the association between thrombophilia and recurrent pregnancy loss and other serious obstetric complications. Study design Electronic databases and manual bibliography searches were used to identify studies evaluating the association between thrombophilia and pregnancy loss, preeclampsia, fetal growth retardation, and placental abruption.

RESULTS

Thrombophilic disorders are associated with an increased risk of fetal loss in the majority of case control and cohort studies. The risk is increased throughout pregnancy, but may be higher in the second and third trimester. The common pathologic finding of placental infarction suggests unexplained fetal loss may result from uteroplacental insufficiency and thrombosis. Thrombophilic disorders are not consistently associated with preeclampsia, fetal growth retardation, or placental abruption. Preliminary data suggest prophylactic anticoagulation may improve outcome in thrombophilic women with unexplained recurrent fetal loss.

CONCLUSION

Women with thrombophilia have an increased risk of pregnancy loss and possibly other serious obstetric complications, although definition of the magnitude of risk will require prospective longitudinal studies. Preliminary data suggesting prophylactic anticoagulation may improve gestational outcome provide a rationale for prospective randomized trials in thrombophilic women with unexplained recurrent fetal loss.

–455G/A β-fibrinogen gene polymorphism, factor V Leiden, prothrombin G20210A mutation and MTHFR C677T, and placental vascular complications

Hyperfibrinogenaemia is associated with systemic arterial and venous thromboembolism and therefore may contribute to placental vascular disease associated with obstetric complications. The fibrinogen-raising -455G/A beta-fibrinogen gene polymorphism may enhance the physiological increase in fibrinogen levels during pregnancy and thereby predispose to obstetric complications. This retrospective case-control study looked at the association between the beta-fibrinogen gene polymorphism -455G/A, the hereditary thrombophilic markers factor V Leiden, prothrombin G20210A mutation (PGM) and C677T methylene tetrahydrofolate reductase (MTHFR), and obstetric complications associated with placental vascular disease. The study group (n = 247) comprised 147 women (90 Caucasian) who met the clinical criteria and a control group of 100 parous women (90 Caucasian) with no history of obstetric or medical complications. No significant differences were observed in the -455A allelic frequencies of the patient and normal control groups, with (allelic frequencies, 0.156 and 0.178, respectively; P = 0.5716, chi2 test, odds ratio = 1.17, 95% confidence interval = 0.65-2.13) or without (allelic frequencies, 0.129 and 0.170, respectively; P = 0.2077, chi2 test, odds ratio = 1.38, 95% confidence interval = 0.81-2.35) the exclusion of non-Caucasian women. There was an increased prevalence of factor V Leiden among Caucasian patients compared with normal controls (allelic frequencies, 0.056 and 0.017, respectively; P = 0.048, chi2 test, odds ratio = 0.29, 95% confidence interval = 0.05-1.15) but there were no differences in the prevalences of PGM or MTHFR. These data suggest that factor V Leiden is associated with an increased risk of obstetric complications, but that the -455A allele of beta-fibrinogen, PGM and MTHFR do not appear to be implicated.

Ethnic differences in the association of factor V Leiden mutation and the C677T methylenetetrahydrofolate reductase gene polymorphism with preeclampsia

OBJECTIVE

This case-control study evaluates the association of the factor V Leiden mutation with preeclampsia and potential synergistic effects of the MTHFR-677T and factor V Leiden mutations with regard to disease risk in two different ethnic populations.

STUDY DESIGN

198 women and their 143 newborns from Germany/Croatia and Indonesia with normal pregnancy or preeclampsia participated in the study. The factor V Leiden mutation was determined by direct sequencing and the MTHFR genotype by a PCR-based RFLP method.

RESULTS

The factor V Leiden mutation is rare in Indonesians. In Germans/Croatians, the frequency of the mutation was significantly increased in mothers with preeclampsia compared to controls. No disease association was found for combined factor V Leiden/MTHFR-677T genotypes on the maternal and fetal level.

CONCLUSIONS

Our results underline the need for a clear distinction of ethnicity in association studies of functional gene polymorphisms. They further support the concept of preeclampsia as a complex disease with variable contributions of disease genes in different ethnic groups.

Thrombophilia and pregnancy

Pregnancy is hypercoagulable state. The field of thrombophilia; the tendency to thrombosis, has been developed rapidly and has been linked to many aspects of pregnancy. It is recently that severe pregnancy complications such as severe preeclampsia intrauterine growth retardation abruptio placentae and stillbirth has been shown to be associated with thrombophilia. Recurrent miscarriage and has also been associated with thrombophilia. Finally, thromboembolism in pregnancy as in the non-pregnant state is linked to thrombophilia. In this review all aspects of thrombophilia in pregnancy are discussed, and also all prophylactic and therapeutic implications.

The search for thrombophilic gene mutations in women with gestational hypertension does not help in predicting poor pregnancy outcome

OBJECTIVE

To evaluate whether genetic thrombophilic mutations, biochemical and biophysical indices help to predict pregnancy outcome in women with gestational hypertension.

DESIGN AND METHODS

A group of 59 women with gestational hypertension were prospectively tested between 24 and 26 weeks of gestation for: (i) DNA analysis to search for gene mutations of Factor V Leiden, prothrombin, methylenetetrahydrofolate reductase and plasminogen activator inhibitor type 1 (PAI-I) polymorphism; (ii) maternal serum concentrations of homocysteine and PAI-1, activated protein resistance and Factor II:C activity levels; (iii) mean uterine arterial resistance index (RI) by Doppler velocimetry; and (iv) history of hypertensive disorders in relatives (the mother and/or the father). Pregnancy outcome was evaluated, and considered 'poor' when patients developed severe pre-eclampsia, haemolysis-elevated liver enzymes-low platelets (HELLP) syndrome, fetal growth restriction (FGR), thromboembolic complications and disseminated intravascular coagulopathy (DIC).

RESULTS

Eighteen women had a poor pregnancy outcome (11 with severe pre-eclampsia, of whom two had superimposed FGR; three with full HELLP syndrome, of whom one had DIC; four with FGR) and delivered, by emergency Caesarean section, neonates with a significantly lower mean gestational age (P < 0.0001) and birthweight (P < 0.0001). History of hypertensive disorders was significantly (P < 0.001) more common in the women group with poor (11 of 18) than normal (10 of 41) outcome. In addition, patients with a poor pregnancy outcome did not have a higher incidence of gene polymorphisms incidence, but significantly (P < 0.01) higher Factor II:C activity levels and significantly (P < 0.0001) higher mean uterine arterial RI than women with normal pregnancy outcome.

CONCLUSIONS

Only Factor II:C activity levels, uterine arterial Doppler and a history of familial hypertension are useful in predicting poor pregnancy outcome in gestational hypertension.

Genetics of preeclampsia: what are the challenges?

Despite recent efforts to identify susceptibility genes of preeclampsia, the genetic determinants of the condition remain ill-defined, as is the situation for most disorders of complex inheritance patterns. The angiotensinogen, factor V, and methylenetetrahydrofolate reductase genes have been investigated in different populations, as have other genes involved in blood pressure, vascular volume control, thrombophilia, lipid metabolism, oxidative stress, and endothelial dysfunction. The study of the genetics of complex traits is faced with both methodological and genetic issues; these include adequate sample size to allow for the identification of modest genetic effects, of gene-gene and gene-environment interactions, the study of adequate quantitative traits and extreme phenotypes, haplotype analyses, statistical genetics, genome-wide (hypothesis-free) versus candidate-gene (hypothesis-driven) approaches, and the validation of positive associations. The use of genetically well-characterized populations showing a founder effect, such as the French-Canadian population of Quebec, in genetic association studies, may help to unravel the susceptibility genes of disorders showing complex inheritance, such as preeclampsia. It is necessary to better evaluate the role of the fetal genome in the resulting predisposition to preeclampsia and its complications. Eventually, we may be able to integrate genetic information to better identify the women at risk of developing preeclampsia, and to improve the management of those suffering from this condition.

Association of Leiden mutation in factor V gene with hypertension in pregnancy and pre-eclampsia: a meta-analysis

OBJECTIVE

To evaluate whether the V Leiden mutation is consistently associated with hypertension in pregnancy across populations of pregnant women.

DESIGN

Meta-analysis of studies comparing women with and without hypertension in pregnancy for the V Leiden mutation.

METHODS

Studies were identified with MEDLINE and EMBASE searches complemented with perusal of bibliographies of retrieved articles and communication with investigators. Data were evaluated with random effects models and between-study heterogeneity was estimated. Sensitivity analyses examined the effect of population and study characteristics. Bias diagnostics evaluated the evolution of the postulated effect over time and the potential for publication bias. RESULTS Across 19 studies (2742 hypertensive women, 2403 controls), V Leiden mutation increased the odds of hypertensive disease of pregnancy by 2.25-fold [95% confidence interval (CI), 1.50-3.38], but there was large between-study heterogeneity (P = 0.002). The results were similar and heterogeneity persisted when sensitivity analyses were limited to studies with Caucasians, proteinuria, diastolic hypertension threshold > 110 mmHg, specified selection of cases, and matching. While studies published up to 2000 showed an odds ratio of 3.16 (95% CI, 2.04-4.92), no association was seen in studies published in 2001-2002 (odds ratio 0.97; 95% CI, 0.61-1.54). There was also evidence of potential publication bias: the five largest studies showed no association (odds ratio 1.21; 95% CI, 0.84-1.74).

CONCLUSIONS

Although modest effects of V Leiden mutation on the risk of hypertension in pregnancy cannot be excluded, the association observed in early and small studies may be typical of bias, in particular time-lag bias and publication bias.

Prenatal screening, epidemiology, diagnosis, and management of preeclampsia

The cause of preeclampsia remains unknown. The disease manifests itself across a broad clinical spectrum from mild to severe, conferring vastly different morbidities and suggesting possibly different disease processes. Oxidative stress, endothelial dysfunction, maternal-fetal immune incompatibility, and abnormal placental implantation are among the suggested causes. The need for a marker or set of markers that allow for definitive diagnosis and assessment of future risk of preeclampsia is tremendous. Ultrasound techniques and several markers have been identified that are increased among patients with preeclampsia, but no test is highly sensitive. In the future, a combination of markers likely will be used to assess risk and, establish the diagnosis, and test treatment strategies. Such an approach would allow for more refined treatment studies of patients who are at highest risk for preeclampsia.

Risk factors for thrombosis in pregnancy

Pregnancy is a hypercoagulable state affecting both the coagulation and the fibrinolytic systems. Any exacerbation of the pre-disposing factors for coagulation may well lead to a thrombotic event more often in pregnant women than in the general population. Arterial thrombosis is very rare in pregnancy. Pre-eclampsia may be a risk factor for the development of arterial disease in later life. Venous thromboembolism (VTE) in pregnancy, although still rare, is a major cause of maternal mortality. Risk factors, such as older age, increased weight and emergency Caesarean section, as well as acquired and genetic thrombophilia, often coexist and reinforce each other. Appropriate thromboprophylaxis needs to be considered and applied on an individual basis. Uteroplacental thrombosis provides a common pathophysiological link between various poor pregnancy outcomes, including recurrent miscarriage, stillbirth, placental abruption, fetal growth restriction and pre-eclampsia. Its significance depends on the gestational age. Acquired and genetic thrombophilia may be associated with such conditions, particularly in early-onset disease. More data are required to assess the significance of such thrombophilias in obstetric practice. Any treatment should be in the context of clinical trials.

Molecular epidemiology of preeclampsia

Numerous articles have been published that address the possible genetic influences on the development of preeclampsia (PE). However, to our knowledge, a complete review of the results has not yet been completed. We undertook a MEDLINE search to identify English-language articles published after January 1, 1990 that examined the possible role of specific genes in the etiology of PE. After a brief introduction and a concise review of the prevailing etiologic hypotheses, we have categorized the candidate genes into six categories, based on their hypothesized role in PE etiology. The purpose of this paper is to review the literature, comment on its quality, and provide a reference for researchers interested in the molecular epidemiology of preeclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to list the prevailing etiologic hypotheses of preeclampsia, to outline the published data on possible genetic influence on the development of preeclampsia, and to clearly state the definition of preeclampsia.

Hiperhomocisteinemia durante el embarazo como factor de riesgo de preeclampsia

A revision about the role of hyperhomocysteinemia in the development of preeclampsia is presented, which summarises our experience in different biochemical and genetic points in relation to this possible association. Plasma total homocysteine concentrations (tHcy) during pregnancy were significantly lower than those of non-pregnant women: 2nd trimester (median, 5.3 micromol/l; range, 3.1-10.0 micromol/l); 3rd trimester (median, 6.3 micromol/l; range, 3.2-13.0 micromol/l). Hyperhomocysteinemia (tHcy>P95) was established as values higher than 7.7 micromol/l in the 2nd trimester, and as values higher than 10.5 micromol/l in the 3rd trimester of pregnancy. We found an association between hyperhomocysteinemia and preeclampsia: tHcy values were significantly higher in the preeclamptic group than in uncomplicated pregnancies; the OR for preeclampsia in hyperhomocysteinemic patients was 7.7 (CI 95%, 1.7-34.8). The other amino acid concentrations were also higher in preeclamptic women. The negative correlation observed between homocysteine and folate in the control group, was not present in preeclamptic women. An association between homocysteine concentrations in preeclampsia and glucose intolerance was not observed. The Doppler study of uterine artery flow velocity waveforms seems to be a good screening method to identify pregnancies at high risk of preeclampsia. The addition of homocysteine determination did not usefully improve its predictive value. The polymorphisms in the main genes involved in folate-homocysteine metabolism studied could not be considered as the determinants of the hyperhomocysteinemia observed in preeclamptic pregnants.

Update on Cobalamin, Folate, and Homocysteine

Three topics affecting cobalamin, folate, and homocysteine that have generated interest, activity, and advances in recent years are discussed. These are: (I) the application of an expanded variety of tools to the diagnosis of cobalamin deficiency, and how these affect and are affected by our current understanding of deficiency; (II) the nature of the interaction between homocysteine and vascular disease, and how the relationship is affected by vitamins; and (III) the improved understanding of relevant genetic disorders and common genetic polymorphisms, and how these interact with environmental influences.

The diagnostic approach to cobalamin deficiency now allows better diagnosis of difficult and atypical cases and more confident rejection of the diagnosis when deficiency does not exist. However, the process has also become a complex and sometimes vexing undertaking. Part of the difficulty derives from the lack of a diagnostic gold standard among the many available tests, part from the overwhelming numerical preponderance of patients with subclinical deficiency (in which isolated biochemical findings exist without clinical signs or symptoms) among the cobalamin deficiency states, and part from the decreased availability of reliable tests to identify the causes of a patient’s cobalamin deficiency and thus a growing deemphasis of that important part of the diagnostic process. In Section I, Dr. Carmel discusses the tests, the diagnostic issues, and possible approaches to the clinical evaluation. It is suggested no single algorithm fits all cases, some of which require more biochemical proof than others, and that differentiating between subclinical and clinical deficiency, despite their overlap, may be a helpful and practical point of departure in the evaluation of patients encountered in clinical practice. The arguments for and against a suggested expansion of the cobalamin reference range are also weighed.

The epidemiologic data suggest that homocysteine elevation is a risk factor for vascular and thrombotic disease. In Section II, Dr. Green notes that the interactions of metabolism and clinical risk are not well understood and a causative relationship remains unproven despite new reports that lowering homocysteine levels may reduce vascular complications. Genetic and acquired influences may interact in important ways that are still being sorted out. The use of vitamins, especially folate, often reduces homocysteine levels but also carries potential disadvantages and even risks. Folate fortification of the diet and supplement use have also markedly reduced the frequency of folate deficiency, and cobalamin deficiency is now the more common deficiency state, especially among the elderly.

Although genetic disorders are rare, they illuminate important metabolic mechanisms and pose diagnostic challenges, especially when clinical presentation occurs later in life. In Section III, Drs. Rosenblatt and Watkins use selected disorders to illustrate the subject. Imerslund-Gräsbeck syndrome, a hereditary disorder of cobalamin absorption at the ileal level, demonstrates genetic heterogeneity. Finnish patients show mutation of the gene for cubilin, the multiligand receptor for intrinsic factor. Surprisingly, Norwegian and other patients have been found recently to have mutations of the AMN (amnionless) gene, mutations that are lethal in mice at the embryonic stage. Two disorders of cobalamin metabolism, cblG and cblE, are now known to arise from mutations of the methionine synthase and methionine synthase reductase genes, respectively. These disorders feature megaloblastic anemia and neurologic manifestations. The folate disorder selected for illustration, methylenetetrahydrofolate reductase (MTHFR) deficiency, paradoxically causes neurological problems but no megaloblastic anemia. This rare deficiency is the most common inborn error of folate metabolism. It is distinct from the very common MTHFR gene polymorphisms, mutations that cause mild to moderate reductions in MTHFR activity but no direct clinical manifestations. The MTHFR polymorphisms, especially the 677C→T mutation, may contribute to vascular and birth defect risks, while reducing the risk of certain malignancies, such as colon cancer. These polymorphisms and those of genes for other enzymes and proteins related to cobalamin, folate, and homocysteine metabolism may be important role players in frequent interactions between genes and the environment.

Susceptibility loci for preeclampsia on chromosomes 2p25 and 9p13 in Finnish families

Preeclampsia is a common, pregnancy-specific disorder characterized by reduced placental perfusion, endothelial dysfunction, elevated blood pressure, and proteinuria. The pathogenesis of this heterogeneous disorder is incompletely understood, but it has a familial component, which suggests that one or more common alleles may act as susceptibility genes. We hypothesized that, in a founder population, the genetic background of preeclampsia might also show reduced heterogeneity, and we have performed a genomewide scan in 15 multiplex families recruited predominantly in the Kainuu province in central eastern Finland. We found two loci that exceeded the threshold for significant linkage: chromosome 2p25, near marker D2S168 (nonparametric linkage [NPL] score 3.77; P=.000761) at 21.70 cM, and 9p13, near marker D9S169 (NPL score 3.74; P=.000821) at 38.90 cM. In addition, there was a locus showing suggestive linkage at chromosome 4q32 between D4S413 and D4S3046 (NPL score 3.13; P=.003238) at 163.00 cM. In the present study the susceptibility locus on chromosome 2p25 is clearly different (21.70 cM) from the locus at 2p12 found in an Icelandic study (94.05 cM) and the locus at 2q23 (144.7 cM) found in an Australian/New Zealand study. The locus at 9p13 has been shown to be a candidate region for type 2 diabetes in two recently published genomewide scans from Finland and China. The regions on chromosomes 2p25 and 9p13 may harbor susceptibility genes for preeclampsia.