Associations between 2 polymorphisms in the methylenetetrahydrofolate reductase gene and placental abruption.

OBJECTIVE: Heritable thrombophilias have been implicated as a potential cause of abruption by vascular disruption at the uteroplacental interface. Polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene have been linked to vascular complications outside of pregnancy, which includes stroke. Given the underlying thrombotic nature of abruption, we hypothesized that polymorphisms in the MTHFR gene are associated with abruption. STUDY DESIGN: We examined 2 variants in MTHFR: 677C-->T and 1298A-->C in genomic DNA extracted from maternal blood from the New Jersey-Placental Abruption Study, an ongoing, multicenter case-controlled study. We identified 195 women with a clinical diagnosis of abruption (cases) and 189 control subjects who were matched on race/ethnicity and parity. We assessed allele and genotype frequencies and their associations with abruption risk after adjusting for confounders through multivariable logistic regression analysis. RESULTS: The wild-type allele (C) frequency of the 677C-->T variant of MTHFR among cases and control subjects was 69.0% and 64.3%, respectively; the wild-type allele (A) of the 1298A-->C variant was 75.9% and 79.4%, respectively. Distributions of the 677C-->T alleles among control subjects violated the Hardy-Weinberg equilibrium (P = .007); distributions of the 1298A-->C alleles were in equilibrium (P = .825). In comparison to the wild-type genotype (C/C), the homozygous mutant form (T/T) of 677C-->T was not associated with abruption (odds ratio, 0.60; 95% confidence interval [CI], 0.33-1.18). Similarly, the homozygous mutant form (C/C) of the 1298A-->C polymorphism was distributed equally between cases and control subjects (odds ratio, 2.28; 95% CI, 0.82-6.35). Plasma homocysteine and vitamin B12, but not folate, concentrations were elevated in cases compared with control subjects among women with the wild-type genotype of MTHFR 677C-->T (P = .039 for homocysteine; P = .048 for B12; P = .224 for folate). CONCLUSION: In this population, neither heterozygosity nor homozygosity for the 677C-->T and 1298A-->C variants in MTHFR was associated with placental abruption.

Platelet inhibitory activity in placentas from normal and abnormal pregnancies.

Retroplacental blood flow requires inhibition of coagulation in the absence of an endothelial lining. We confirmed that trophoblast releases an inhibitor of platelet aggregation which functions via degradation of adenosine diphosphate. This inhibitor appears to be deficient in some pregnancies with abruptio placentae and intrauterine growth retardation. Unimpeded retroplacental blood flow may depend upon the local inhibition of platelet aggregation. Placental tissue contains an inhibitor of platelet aggregation which appears to be an adenosine diphosphatase distinct from heat-stable alkaline phosphatase. Placental tissue from patients with abruptio placentae contains abnormally low amounts of this enzyme.

Low-activity haplotype of the microsomal epoxide hydrolase gene is protective against placental abruption.

OBJECTIVE: We wanted to determine whether genetic variability in the gene encoding microsomal epoxide hydrolase (EPHX) contributes to individual differences in susceptibility to the occurrence of placental abruption. METHODS: The study involved 117 women with placental abruption and 115 healthy control pregnant women who were genotyped for two single nucleotide polymorphisms (SNPs), T-->C (Tyr113His) in exon 3 and A-->G (His139Arg) in exon 4, in the EPHX gene. Chi-square analysis was used to assess genotype and allele frequency differences between the women with placental abruption and the control group. In addition, single-point analysis was expanded to pair of loci haplotype analysis to examine the estimated haplotype frequencies of the two SNPs, of unknown phase, among the women with placental abruption and the control group. Estimated haplotype frequencies were assessed using the maximum-likelihood method, employing an expectation-maximization algorithm. RESULTS: Single-point allele and genotype distributions in exons 3 and 4 of the EPHX gene were not statistically different between the groups. However, in the haplotype estimation analysis we observed a significantly decreased frequency of haplotype C-A (His113-His139) among the placental abruption group compared with the control group (P = .007). The odds ratio for placental abruption associated with the low-activity haplotype C-A (His113-His139) was 0.552 (95% confidence interval, 0.358 to 0.851). CONCLUSIONS: The use of two intragenic SNPs jointly in haplotype analysis of association demonstrated that the genetically determined low-activity haplotype C-A (His113-His139) was significantly less frequent in women with placental abruption.

Thrombin-enhanced matrix metalloproteinase-1 expression: a mechanism linking placental abruption with premature rupture of the membranes.

OBJECTIVE: Given the strong clinical association between the decidual hemorrhage of placental abruption and subsequent preterm premature rupture of the membranes, we assessed the effects of thrombin on the expression of the potent interstitial collagenase, matrix metalloproteinase-1 (MMP-1), in cultured endometrial stromal and decidual cells. STUDY DESIGN: Stromal cells derived from predecidualized cycling endometrium and decidual cells from term decidua were cultured in a defined medium containing estradiol, to mimic the hormonal milieu of the non-pregnant proliferative phase, or estradiol plus medroxyprogesterone acetate (MPA), to mimic the hormonal milieu of pregnancy, in the presence and absence of thrombin. Culture media were examined for MMP-1 protein levels and cell lysates were examined for steady-state MMP-1 mRNA levels. RESULTS: MPA strongly inhibited MMP-1 levels in endometrial stromal and term decidual cells. However, thrombin overcame this suppression, producing MMP-1 levels that were several-fold higher than control levels. CONCLUSION: Extrapolation of thrombin-enhanced MMP-1 expression in cultured endometrial stromal and decidual cells to the in vivo pregnant state provides an explanation for the strong association between placental abruption and preterm membrane rupture.

Polymorphisms in methionine synthase reductase and betaine-homocysteine S-methyltransferase genes: risk of placental abruption.

OBJECTIVES: Methionine synthase reductase (MTRR) and betaine-homocysteine S-methyltransferase (BHMT) are two enzymes that regulate homocysteine metabolism. Elevated homocysteine (hyperhomocysteinemia) is associated with adverse pregnancy outcomes and vascular disease. We assessed whether polymorphisms in MTRR (66A-->G; I22M) and BHMT (742G-->A; R239Q) were associated with abruption. We further evaluated whether homocysteine levels differed between cases and controls for MTRR and BHMT genotypes. METHODS: Data were derived from the New Jersey Placental Abruption Study (NJ-PAS)-an ongoing, multicenter, case-control study since August 2002. Women with a clinical diagnosis of abruption were recruited as incident cases (n=196), and controls (n=191) were matched to cases based on maternal race/ethnicity and parity. Total plasma homocysteine concentrations were evaluated in a subset of 136 cases and 136 controls. DNA was genotyped for the MTRR and BHMT polymorphisms. RESULTS: Frequencies of the minor allele of MTRR were 40.8% and 42.2% in cases and controls, respectively (adjusted OR 0.79, 95% CI 0.45, 1.40). The corresponding rates for BHMT were 33.9% and 31.7%, respectively (adjusted OR 1.93, 95% CI 0.99, 4.09). Distributions for the homozygous mutant form of MTRR were similar between cases and controls (OR 1.18, 95% CI 0.62, 2.24). The rate of homozygous mutant BHMT genotype was 2.8-fold (OR 2.82, 95% CI 1.84, 4.97) higher in cases than controls. Stratification of analyses based on maternal race did not reveal any patterns in association. CONCLUSIONS: In this population, there was an association between the homozygous mutant form of BHMT (742G-->A) polymorphism and increased risk for placental abruption.

MTHFD1 R653Q polymorphism is a maternal genetic risk factor for severe abruptio placentae.

This study examined the relationship between folate/homocysteine-related genetic polymorphisms: MTHFD1 1958G --> A (R653Q), MTHFR 677C --> T (A222V), MTHFR 1298A --> C (E429A), and risk of severe abruptio placentae. We genotyped 62 women with a pregnancy history complicated by severe abruptio placentae and 184 control pregnancies. Analysis of the MTHFD1 1958G --> A (R653Q) polymorphism showed increased frequency of the 'QQ' homozygote genotype in pregnancies affected by severe abruptio placentae compared to control pregnancies (odds ratio 2.85 (1.47-5.53), P = 0.002). In contrast to previous reports, the MTHFR polymorphisms 677C --> T (A222V) and 1298A --> C (E429A) were not associated with abruptio placentae risk in our cohort, when analyzed either independently or in combination. We conclude that women who are 'QQ' homozygote for the MTHFD1 1258G --> A (R653Q) polymorphism are almost three times more likely to develop severe abruptio placentae during their pregnancy than women who are 'RQ' or 'RR.'

The Glu298Asp variant of the endothelial nitric oxide synthase gene is associated with an increased risk for abruptio placentae in pre-eclampsia.

Attempts to define a pre-eclampsia susceptibility profile have been hampered by the wide clinical spectrum of the condition and the complex genetics underlying it. Genes that modulate blood pressure, fluid homeostasis and placental vascular development have been considered plausible candidates. Among these are the angiotensinogen (AGT) gene variant Met235Threo, which has been associated with pre-eclampsia and the endothelial nitric oxide synthase (eNOS) polymorphism Glu298Asp, which has been associated with both pre-eclampsia and abruptio placentae, a condition that often co-exists with pre-eclampsia. The aim of this study was to investigate a potential association between these gene variants and pre-eclampsia with and without abruptio placentae in a South African patient group. Fifty primigravidas with early onset, severe pre-eclampsia, 50 women presenting primarily with abruptio placentae (whether associated with pre-eclampsia or not) and a control panel of 50 healthy pregnant women constituted the study groups. The Met235Threo and Glu298Asp variants were characterised by polymerase chain reaction and restriction enzyme analysis. No association was demonstrated between the M235T variant of the AGT gene and pre-eclampsia or abruptio placentae. In contrast, the combined frequency of the eNOS variant genotypes (GT and TT) was significantly higher in the abruptio placentae group (49%) than the control group (21%) (p=0.006). Furthermore, in the pre-eclampsia patients who subsequently developed abruptio placentae, the eNOS GT genotype emerged as a major risk factor for the development of abruptio placentae (p<0.0001). These data suggest that the presence of a Glu298Asp eNOS variant may pre-dispose a pre-eclamptic woman to develop abruptio placentae or that it is a marker for predisposition.

The missense Glu298Asp variant of the endothelial nitric oxide synthase gene is strongly associated with placental abruption.

We recently identified a missense variant (Glu298Asp) that lies within exon 7 of the endothelial nitric oxide synthase (eNOS) gene, and that is associated with severe preeclampsia (proteinuric hypertension that develops as a consequence of pregnancy). Maternal hypertension is the most consistently identified factor predisposing to placental abruption. Our objective, therefore, was to analyze the association between the Glu298Asp eNOS gene variant and placental abruption. The study participants included 35 patients with histories of placental abruption and 170 control subjects. Screening for the Glu298Asp eNOS gene variant was carried out by analysis of polymerase chain reaction/restriction fragment length polymorphism. The analyses revealed that the frequency of the Glu298Asp variant (Glu298Asp homozygotes and heterozygotes) was significantly (P<0.001) higher in the placental abruption group (n=14; 40%) than in the control group (n=24; 14%). We conclude that the presence of the Glu298Asp eNOS gene variant could be a marker of increased risk of developing placental abruption.

Matrix metalloproteinase 9 activity in urine of patients at risk for premature delivery.

A simple, noninvasive assay was used to quantitate urinary matrix metalloproteinase 9 activity among 15 patients with threatened premature labor. Both positive and negative predictive values for risk for premature delivery were 80%.