Thrombophilias as risk factors for disorders of pregnancy and fetal damage

MTHFR C677T Polymorphism is Not Associated with Placental Abruption or Preeclampsia in Finnish Women

OBJECTIVE

The aim of our study was to examine genetic variability in the gene encoding methylenetetrahydrofolate reductase (MTHFR) and individual susceptibility to the placental abruption or preeclampsia.

METHODS

362 women (133 with preeclampsia, 117 with placental abruption, and 112 healthy controls) were genotyped for C677T polymorphism in the MTHFR gene.

RESULTS

Similar genotype distributions were observed in the frequencies of C/C homozygotes (58.6%, 64.1%, and 57.1% for the three groups, respectively) and mutant homozygotes T/T (9.0%, 5.1% and 5.4%). No significant differences were detected in T allele frequencies (25.2%, 20.5%, and 24.1% for the three groups, respectively).

CONCLUSIONS

MTHFR C677T polymorphism does not have a major role in the development of preeclampsia or placental abruption in the Finnish population.

Homocysteinemia is inversely correlated with platelet count and directly correlated with sE- and sP-selectin levels in females homozygous for C677T methylenetetrahydrofolate reductase

Plasma homocysteine levels depend in part on the molecular nature of the methylenetetrahydrofolate reductase (MTHFR) and on blood folate intake. Little has been reported on platelet counts in the presence of hyperhomocysteinemia and MTHFR polymorphisms, with the exception of delayed platelet recovery in homozygous MTHFR C677T subjects after treatment with methotrexate for ovarian cancer. The aim of this investigation was to evaluate the possibility of a link between the platelet count and plasma homocysteine levels in different MTHFR variants in 165 female patients. Determinations of plasma homocysteine levels were by ELISA and of MTHFR polymorphisms (A1298C and C677T) were by inverse hybridization. Serum P- and E-selectin concentrations were obtained by ELISA. An inverse correlation (R=-0.88, P<0.001) was observed between blood platelet counts and plasma homocysteine levels in the women homozygous for MTHFR C677T. This correlation did not depend on pregnancy or other variables reported. Serum concentrations of sE- and sP-selectin, markers of endothelial and platelet activation, were significantly and positively correlated with homocysteine levels. These findings suggest that homocysteine affects platelet numbers in women with MTHFR C677T possibly consequent to endothelial and platelet activation.

Independent risk factors for cesarean section among women with thrombophilia

OBJECTIVE To determine the prevalence of cesarean section (CS) in pregnant women with a diagnosis of thrombophilia and to identify risk factors for CS.

STUDY DESIGN

The women were recognized by an ICD-9 code from a computerized database. Maternal records were reviewed between the years 2000 and 2005. Pregnancy characteristics of 86 women with thrombophilia were compared according to the mode of delivery: CS (n = 18) versus vaginal delivery (n = 68).

RESULTS

The prevalence of CS in the study population was 21% (18/86). Women with CS had a lower gestational age at delivery (P = 0.019), lower birth weight (P = 0.048), higher incidence of the following: preterm delivery (P < 0.001), gestational hypertension (P = 0.028), intrauterine growth retardation/antepartum death/placental abruption (P = 0.065) and non-reassuring fetal heart rate (NRFHR) monitoring (P < 0.001) compared to those with vaginal delivery. In a multiple logistic regression analysis only NRFHR monitoring, birth weight and malpresentation remained statistically significant.

CONCLUSION

CS in women with thrombophilia are associated with common obstetrical causes rather than specific thrombophilia dependent factors.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Ethical and clinical practice considerations for genetic counselors related to direct-to-consumer marketing of genetic tests

Several companies utilize direct-to-consumer (DTC) advertising for genetic tests and some, but not all, bypass clinician involvement by offering DTC purchase of the tests. This article examines how DTC marketing strategies may affect genetic counselors, using available cardiovascular disease susceptibility tests as an illustration. The interpretation of these tests is complex and includes consideration of clinical validity and utility, and the further complications of gene-environment interactions and pleiotropy. Although it is unclear to what extent genetic counselors will encounter clients who have been exposed to DTC marketing strategies, these strategies may influence genetic counseling interactions if they produce directed interest in specific tests and unrealistic expectations for the tests' capacity to predict disease. Often, a client's concern about risk for cardiovascular diseases is best addressed by established clinical tests and a family history assessment. Ethical dilemmas may arise for genetic counselors who consider whether to accept clients who request test interpretation or to order DTC-advertised tests that require a clinician's authorization. Genetic counselors' obligations to care for clients extend to interpreting DTC tests, although this obligation may be fulfilled by referral or consultation with specialists. Genetic counselors do not have an obligation to order DTC-advertised tests that have minimal clinical validity and utility at a client's request. This can be a justified restriction on autonomy based on consideration of risks to the client, the costs, and the implications for society.

The clot thickens

Vascular sclerosis has been linked to many risk factors, including smoking, family history, low birth weight, and hypertension. In interesting studies, Goforth et al. show an increased rate of mutations in thrombophilic molecules in patients with vascular sclerosis in renal biopsies, suggesting yet another mechanism.