BACKGROUND Consanguinity - or marriage between close blood relatives, in particular first cousins - is widely practised and even socially encouraged in many countries. However, in the face of fertility transition where the number of cousins eligible to marry declines, how might such constraints on consanguinity develop in the future? OBJECTIVE Numerous studies have stated that the practice cannot continue at present levels and in its present form in the face of fertility transition. However, the future impact of fertility transition on availability of cousins to marry has not yet been quantified. METHODS We perform a simulation exercise using past and projected net reproduction rates (NRRs) derived from the UN. We calculate the average number of cousins of the opposite sex as a function of the average number of children, the average probability of an individual having at least one eligible paternal cousin of the opposite sex, and conclude with an examination of constraints on consanguineous marriage in selected countries under different fertility assumptions. RESULTS Current and projected fertility levels in Middle Eastern countries will create challenging constraints on the custom once today's birth cohorts reach marriageable age. CONCLUSIONS Either consanguinity prevalence will diminish significantly, or the institution will be forced to adapt by becoming more coercive in the face of reduced choice or at the expense of other social preferences (such as for an older groom wedding a younger bride). Fertility decline affects prospects for social change not only through its well-known consequences for mothers but also through shaping marriage conditions for the next generation.

More than 1 billion people live in societies where consanguineous marriages are common. When children are born to consanguineous unions, there is an increased probability of the expression of single-gene disorders with a recessive mode of inheritance. There are presumptive social benefits of consanguineous marriages reported in the literature. METHODS: The UK's Born in Bradford birth cohort study recruited 12 453 women at 26-28 weeks' gestation between 2007 and 2010. In all, 11 396 completed a questionnaire, including questions about their relationship to their baby's father. We compared Pakistani and Other ethnic groups in consanguineous relationships and Pakistani, Other and White British groups not in consanguineous relationships, calculating percentages and age-adjusted prevalence ratios (95% confidence intervals). RESULTS: In the Pakistani group, 59.3% of women (n = 3038) were blood relatives of their baby's father. Consanguinity was uncommon in the Other ethnic group (7.3%, n = 127) and rare (n = 5) in the White British group. Compared with non-consanguineous counterparts, mothers in consanguineous relationships were socially and economically disadvantaged (e.g. never employed, less likely to have higher education). The Pakistani consanguineous group's social, economic and health lifestyle circumstances were equivalent to, in some cases better than, women in non-consanguineous relationships (e.g. up-to-date in paying bills, or in disagreeing that they wished for more warmth in their marital relationship). The consanguineous relationship group had less separation/divorce. Rates of cigarette smoking during pregnancy were lower in mothers in consanguineous relationships. CONCLUSION: Debate about consanguinity should balance the potential protective effect of consanguineous relationships with established genetic risk of congenital anomaly in children.

This thesis consists of three essays in applied microeconomics: First, heat and school absence: evidence from a survey of Indian children. Second, heatwaves and short-term morbidity in India. Third, intra-family marriage and pregnancy outcomes. Chapter 1. India is the second most populous country on earth with young people representing a significant number of the population resulting in data that indicates such figures at 38 per cent. With such high numbers, major consideration must be given into developing informed and targeted policies to ensure positive educational outcomes for young people. This paper contributes to existing literature by investigating the impact of high temperatures on students’ rates of absenteeism, relying on the short-term exogenous variation in daily maximum temperatures. The paper highlights the heterogeneity of the effect of temperature by climate zone. To create data, we link information on children’s school absences from the India Human Development Survey (IHDS-II) in combination with meteorological data from the ERA-Interim archive taken from a thirty day period prior to individual interview dates. Our findings suggest that high temperatures have a substantial negative impact on students’ attendance in rural areas. However, limited evidence of such an effect is found in urban areas. Our results therefore indicate a need to implement future in-depth studies. Chapter 2. Within this chapter, we investigate the impact of prolonged heat exposure on individuals short-term morbidity rates over a thirty day period prior to the interview date. We work with a broad dataset and use an econometric model that utilizes plausibly exogenous variation in high weather temperatures. We implement the percentile-based approach and three different heatwave metrics as a innovative way of defining and capturing the impact of heatwaves on health outcomes. Our results show that heatwave intensity of the eighty-fifth percentile over the duration of three consecutive days of extensive heat has a significant adverse effect on individuals short-term morbidity. More so, our findings indicate a disparity between genders in relation to the impact of heatwaves. Finally, it can be suggested that individuals having to travel an extensive distance in order to access water are most affected by high temperatures. Chapter 3. Millions of people worldwide are married to their blood relatives, yet the resulting impact on offspring health continues to be debated. Within this paper, we provide evidence around this debate by studying the birth outcomes from a large, representative sample of Indian women in varying marital circumstances. We explore the impact of intra-family marriage on negative pregnancy outcomes including stillbirth, miscarriage, and child death after birth. We utilize an ordinary least squares model (OLS), which controls for a wide range of financial and family factors. The results show that being a woman related to her husband by blood increases the probability of experiencing negative pregnancy outcomes by 2.8 percentage points. Our finding is robust using the instrumental variable approach (IV). The instrumental variable represents the ambient level of violence against women, which positively affects the probability of consanguineous marriage. The IV approach leads to a slightly smaller adverse impact of 2.2 percentage points. In addition, the OLS results provide suggestive evidence that intra-family marriage has no heterogeneous impact across religion types.