The practice of consanguineous marriage in oman: prevalence, trends and determinants

The practice of consanguineous marriage has been the culturally preferred form of marriage in most Arab and the Middle Eastern countries, including Oman, but due to a paucity of population-based data in the past there is a dearth of information about its form and dynamics in Oman. Recent national-level surveys allow this gap to be filled. This paper examines the prevalence, trends and determinants of consanguineous marriages in Oman using data from the 2000 Oman National Health Survey. The results indicate a very high prevalence of consanguineous marriage in Oman, as more than half (52%) of marriages are consanguineous. First cousin unions are the most common type of consanguineous unions, constituting 39% of all marriages and 75% of all consanguineous marriages. The study observed various patterns of consanguinity, some of them common with other Arab nations, and some unique in nature. Women's age at marriage, employment, place of childhood residence and geographical region appear to be significant determinants of consanguineous marriages. Consanguineous marriage shows a strong association with marital stability, early age at marriage and early-age childbearing. There has been no appreciable change in the prevalence of consanguineous unions in Oman over the last four decades despite massive socioeconomic development and modernization. However, recent marriage cohorts show slight declining trends. The results suggest that consanguinity is likely to remain stable in the future or decline at a slow rate. Specific health education and genetic counselling should be followed in line with WHO recommendations to minimize the negative health consequences of consanguinity for child health.     

Rural-urban migration and child survival in urban Bangladesh: are the urban migrants and poor disadvantaged?

This paper analyses the levels and trends of childhood mortality in urban Bangladesh, and examines whether children's survival chances are poorer among the urban migrants and urban poor. It also examines the determinants of child survival in urban Bangladesh. Data come from the 1999-2000 Bangladesh Demographic and Health Survey. The results indicate that, although the indices of infant and child mortality are consistently better in urban areas, the urban-rural differentials in childhood mortality have diminished in recent years. The study identifies two distinct child morality regimes in urban Bangladesh: one for urban natives and one for rural-urban migrants. Under-five mortality is higher among children born to urban migrants compared with children born to life-long urban natives (102 and 62 per 1000 live births, respectively). The migrant-native mortality differentials more-or-less correspond with the differences in socioeconomic status. Like childhood mortality rates, rural-urban migrants seem to be moderately disadvantaged by economic status compared with their urban native counterparts. Within the urban areas, the child survival status is even worse among the migrant poor than among the average urban poor, especially recent migrants. This poor-non-poor differential in childhood mortality is higher in urban areas than in rural areas. The study findings indicate that rapid growth of the urban population in recent years due to rural-to-urban migration, coupled with higher risk of mortality among migrant's children, may be considered as one of the major explanations for slower decline in under-five mortality in urban Bangladesh, thus diminishing urban-rural differentials in childhood mortality in Bangladesh. The study demonstrates that housing conditions and access to safe drinking water and hygienic toilet facilities are the most critical determinants of child survival in urban areas, even after controlling for migration status. The findings of the study may have important policy implications for urban planning, highlighting the need to target migrant groups and the urban poor within urban areas in the provision of health care services.     

Fertility transition in Bangladesh: understanding the role of the proximate determinants

Bangladesh has been passing through a crucial phase of fertility transition. The level of fertility declined dramatically during the early 1990s without any remarkable improvement in socioeconomic and health status, and then remained constant at a high level of 3.3, despite the increased use of contraception. Such fertility transition can be traced to variations in one or more of the proximate or direct determinants of fertility. This paper critically analyses the fertility levels in Bangladesh with a view to exploring the possible explanations of fertility decline in the 1990s and then its stabilization. The main focus of the study is to examine the role of the major proximate determinants of fertility in bringing about the change in fertility level in Bangladesh. The data for the study come from a series of nationally representative surveys over the period of 1975 to 1999-2000. The analysis indicates that fertility has temporarily ceased to decline in recent years due to the 'tempo' effect of high past fertility, but in general a declining trend in fertility is underway. The analysis suggests that the fall in fertility is consistent with the underlying trends in most important proximate determinants of fertility. In recent years contraception has emerged as the highest fertility reducing factor in Bangladesh and its effect is greatest in middle and older age groups. Although until the early 1990s postpartum lactational infecundability was the most important and strongest fertility reducing factor in Bangladesh, in recent years its fertility inhibiting effect has gradually decreasing owing to the declining trend in the lactational infecundability period. The analysis reveals that although the fertility reducing effect of the marriage pattern is increasing, its effect is offset by the declining trend in the lactational infecundability period. A review of these two variables suggests that their effect cannot be raised much for prevailing socioeconomic and cultural reasons, and any future reduction in fertility in Bangladesh may be largely dependent on increased use of effective birth control methods.     

Fertility intentions and subsequent fertility behaviour in Matlab: do fertility intentions matter?

This study examines the extent of the interrelationship between future fertility intention and subsequent fertility behaviour in rural Bangladesh using longitudinal data. It confirms that fertility intention is an important predictor of subsequent fertility behaviour for rural Bangladeshi women. Women wanting no more children are over three times less likely to have a child during a 5-year follow-up than those wanting more children. A multivariate model using logistic regression shows that fertility intention is a useful indicator for fertility behaviour, when background and life-cycle variables are controlled. The different patterns of fertility intentions by socioeconomic and demographic subgroups suggest that different programme strategies should be designed for specific target groups.     

Dissecting metabolic flux in C<Subscript>4</Subscript> plants: experimental and theoretical approaches

C₄ photosynthesis is the carbon fixation pathway in specific plant species, so called C₄ plants including maize, sorghum and sugarcane. It is characterized by the carboxylation reaction that forms four-carbon (C₄) molecules, which are then used to transport CO₂ to the proximity of RubisCO in the bundle sheath cells. Since C₄ photosynthesis confers high photosynthetic as well as water and nitrogen use efficiency on plants, worldwide efforts have been made to understand the mechanisms of C₄ photosynthesis and to properly introduce the pathway into C₃ crops. Metabolic flux analysis (MFA) is a research field trying to analyze the metabolic pathway structure and activity (i.e., flux) in vivo. Constraint-based reconstruction and analysis tools theoretically study the distribution of metabolic flux in genome-scale network-based models. Different types of MFA and model-based analyses have been contributing to the discovery of C₄ photosynthetic pathways and to analyze its operation in C₄ plant species. This article reviews the studies to dissect the operation of C₄ photosynthesis and adjacent pathways, from the pioneer studies using radioisotope-based MFA to the recent stable isotope-based MFA and the model-based approaches. These studies indicate complex interconnections among metabolic pathways and the importance of the integration of experimental and theoretical approaches. Perspectives on the integrative approach and major obstacles are also discussed.