RESUMEN
Numerous studies have evaluated the association between the maternal C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene and congenital heart defect (CHD) risk in the Chinese Han population. However, the specific association is still controversial. Six separate studies with 1089 subjects in the Chinese Han population on the relationship between the C677T polymorphism and CHDs were analyzed by meta-analysis, upon database search. The fixed-effect model or random-effect model was selected to calculate the pooled odds ratio (ORs) and its corresponding 95% confidence interval (95%CI) when appropriate. The Begg test was used to measure publication bias. Sensitivity analyses were performed to insure authenticity of the outcome. Meta-analysis of the results showed significant associations between the maternal C677T polymorphism and CHD risk (CC vs TT: OR = 0.65, 95%CI = 0.44-0.96). Limiting the analysis to the studies with controls in the Hardy-Weinberg equilibrium and the results indicate that the meta-analysis was statistically significant. Results of Begg's funnel plot showed that there was no publication bias (all P > 0.05). The present meta-analysis suggested that the maternal C677T polymorphism is a risk factor for CHDs in the Chinese Han population.
Asunto(s)
Cardiopatías Congénitas/genética , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Polimorfismo de Nucleótido Simple , Pueblo Asiatico , Estudios de Casos y Controles , Femenino , Frecuencia de los Genes , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Cardiopatías Congénitas/enzimología , Humanos , Factores de RiesgoRESUMEN
PIP: Blake hypothesized in 1955 that the instability of reproductive unions may affect fertility in 2 opposite ways - it may reduce the rate of reproduction by decreasing the total time of exposure to pregnancy, and it may increase the rate of reproduction because there is often a desire to have children born of each new union or simply because coitus is more frequent at the start of each new union. Independent measurements of the effects on fertility of these 2 components are presented in order to test a modified form of Blake's hypothesis. The source of data for this analysis is the Urban In-Migration and Fertility Survey conducted in Guayaquil, Ecuador, in 1971. When the number of unions was controlled for, a negative correlation between fertility and years of reproductive time loss was found among men, but the evidence among the female population was not conclusive. Women with less than 1 year of loss had .7 fewer children than women with 1-3 years of loss. This is a significant difference which cannot be explained by sampling error. When years spent in union was controlled for, individuals who had 2 unions had a 14% higher fertility rate than those who had been in only 1 union. Similar results were found for both the male and female populations. These findings support the hypothesis that multiplicity of sexual unions has a positive effect on fertility. The desire for children in the current union seems to be stronger among the Ecuadorian men. It can be concluded that in societies where people enter new unions soon after dissolution of a previous union, instability will have a positive effect upon fertility. Instability will tend to reduce fertility in societies where people spend a long time in interunion or postunion celibacy.^ieng