The impact of the stopping rule on sex ratio of last births in Vietnam

This study examines the hypothesis that the stopping rule - a traditional postnatal sex selection method where couples decide to cease childbearing once they bear a son - plays a role in high sex ratio of last births (SRLB). The study develops a theoretical framework to demonstrate the operation of the stopping rule in a context of son preference. This framework was used to demonstrate the impact of the stopping rule on the SRLB in Vietnam, using data from the Population Change Survey 2006. The SRLB of Vietnam was high at the level of 130 in the period 1970-2006, and particularly in the period 1986-1995, when sex-selective abortion was not available. Women were 21% more likely to stop childbearing after a male birth compared with a female birth. The SRLB was highest at parity 2 (138.7), particularly in rural areas (153.5), and extremely high (181.9) when the previous birth was female. Given the declining fertility, the stopping rule has a potential synergistic effect with sex-selective abortion to accentuate a trend of one-son families in the population.     

Gene-Culture Coevolution and Sex-Ratios: The Effects of Infanticide, Sex-Selective Abortion, Sex Selection, and Sex-Biased Parental Investment on the Evolution of Sex Ratios

The evolutionary consequences of culturally transmitted practices that cause differential mortality between the sexes, thereby distorting the sex ratio (e.g., female infanticide and sex-selective abortion), are explored using dynamic models of gene-culture coevolution. We investigate how a preference for the sex of offspring may affect the selection of genes distorting the primary sex ratio. Sex-dependent differences in mortality have been predicted to select for a male- or female-biased primary sex ratio, to have no effect, or to favor either under different circumstances. We find that when a mating pair′s behavior modifies mortality rates in favor of one sex, but does not change the number of offspring produced in the mating, the primary sex ratio will evolve a bias against the favored sex However, when the total number of offspring of a mating pair is significantly seduced as a consequence of their prejudice, the primary sex ratio will evolve to favor the preferred sex. These results hold irrespective of whether the sex ratio is distorted by the mother′s, the father′s or the individual′s own autosomal genes. The use of dynamic models of gene-culture coevolution allows us to explore the evolution of alleles which distort the sex ratio, as well as the final equilibrium states of the system. Gene-culture interactions can provide equilibria different from those in purely genetic systems, slow the approach to these equilibria by orders of magnitude, and move the primary (PSR) and the adult sex ratio (ASR) away from any stable equilibrium for hundreds of generations.     

Sex selection and restricting abortion and sex determination

Sex selection in India and China is fostered by a limiting social structure that disallows women from performing the roles that men perform, and relegates women to a lower status level. Individual parents and individual families benefit concretely from having a son born into the family, while society, and girls and women as a group, are harmed by the widespread practice of sex selection. Sex selection reinforces oppression of women and girls. Sex selection is best addressed by ameliorating the situations of women and girls, increasing their autonomy, and elevating their status in society. One might argue that restricting or prohibiting abortion, prohibiting sex selection, and prohibiting sex determination would eliminate sex selective abortion. But this decreases women's autonomy rather than increases it. Such practices will turn underground. Sex selective infanticide, and slower death by long term neglect, could increase. If abortion is restricted, the burden is placed on women seeking abortions to show that they have a legally acceptable or legitimate reason for a desired abortion, and this seriously limits women's autonomy. Instead of restricting abortion, banning sex selection, and sex determination, it is better to address the practice of sex selection by elevating the status of women and empowering women so that giving birth to a girl is a real and positive option, instead of a detriment to the parents and family as it is currently. But, if a ban on sex selective abortion or a ban on sex determination is indeed instituted, then wider social change promoting women's status in society should be instituted simultaneously.     

Son preference and intimate partner violence victimization in India: examining the role of actual and desired family composition

Son preference has been considered as a determinant of women's risk of intimate partner violence (IPV) experience in India, although quantitative evidence from large nationally representative studies testing this relationship is limited. This study examines the association between husband's son preference, sex composition of children and risk of physical and sexual IPV victimization among wives. Information was collected for 26,284 couples in the nationally representative 2005-2006 National Family Health Survey of India. The exposures were husband's son preference measured as husband's desire for one or more sons greater than the number of daughters and sex composition of the household: only sons, only daughters and mixed. Outcome included past year physical and/or sexual IPV. The results showed that husband's reported son preference (RR: 1.05; 95% CI: 0.98-1.13) and sex composition of children were not associated with risk for IPV victimization in the models adjusted for socio-demographic factors. The findings from this first population-based study of socio-cultural norms around son preference and married Indian women's risk for IPV victimization indicate that cultural preference for sons does not influence women's risk for IPV victimization.     

Hormonal control of sex ratio

It has been hypothesized that the maternal gonadotrophin level at the time of conception is causally related to the sex of the resultant human zygote, high levels of hormone being associated with the production of female offspring. In this note, evidence for and against this hypothesis is reviewed. There seems so much evidence in its favour that one might conclude that it contains at least a kernel of truth. It is suggested here that of the components of gonadotrophin, the active one in this hypothesized sex-selective process is luteinizing hormone, rather than follicle-stimulating hormone. The hypothesis is nevertheless unable to accommodate several well-established sets of data. Accordingly it is suggested that other hormones, oestrogen and testosterone, have sex-selective properties too, high levels being associated with male offspring. This elaboration of the hypothesis, if it were true, would explain most, if not all, of the epidemiological data on the human secondary sex ratio. In particular it would explain Guerrero's data which have hitherto resisted explanation of any kind. No suggestion is made about possible mechanisms underlying these hypothesized sex-selective properties. But it seems that sex-selective abortion is not the only one. It is hoped that other workers may be stimulated not only to test the hypothesis as outlined here, but--if it survives this testing--to suggest such mechanisms.     

Recent Increase in Sex Ratio at Birth in Viet Nam

Introduction

Since the 1980s, sex ratio at birth (male births per 100 female births) has increased in many Asian countries as a result of selective abortions, but to date there has been no such evidence for Viet Nam. Our aim in this paper is to ascertain the situation with respect to sex ratio at birth in Viet Nam over the past five years.

Materials and Methods

Original data were obtained from sample population surveys in Viet Nam recording annual birth rates since 2000 of about 450,000 women, as well as from two successive birth surveys conducted for the first time in 2007 (1.1 million births). The annual population surveys include specific information on birth history and mothers'' characteristics to be used for the analysis of trends and differentials in sex ratio at birth.

Results and Discussion

Birth history statistics indicate that the SRB in Viet Nam has recorded a steady growth since 2001. Starting from a level probably close to the biological standard of 105, the SRB reached 108 in 2005 and 112 in 2006, a value significantly above the normal level. An independent confirmation of these results comes from the surveys of births in health facilities which yielded a SRB of 110 in 2006–07. High SRB is linked to various factors such as access to modern health care, number of prenatal visits, level of higher education and employment status, young age, province of residence and prenatal sex determination. These results suggest that prenatal sex determination followed by selective abortion has recently become more common in Viet Nam. This recent trend is a consequence of various factors such as preference for sons, declining fertility, easy access to abortion, economic development as well as the increased availability of ultrasonography facilities.     

Two sons and a daughter: sex composition and women's reproductive behaviour in madhya pradesh, India

Summary This article examines how the sex composition of women's current children at the start of a pregnancy interval influences both fertility desires and the full range of reproductive actions women may take to realize them, including temporary contraception, abortion and sterilization, in Madhya Pradesh, India, where popular notions of ideal family size and sex composition are dominated by son preference. The analysis is conducted using a dataset of 9127 individual pregnancy intervals from a 2002 statewide representative survey of 2444 women aged 15-39 with at least one child. The results indicate that women's preferences go beyond a singular preference for male children, with the preferred composition of children being two boys and one girl. Women with this composition are 90% less likely to report having wanted another pregnancy (OR 0.097, p<0.01) relative to those with two girls. These preferences have significant implications for reproductive actions. While sex composition has no statistically significant effect on the use of temporary contraception, those with the preferred sex composition are twice as likely to attempt abortion (OR 2.436, p<0.01) and twelve times more likely to be sterilized (OR 12.297, p<0.01) relative to those with two girls only.     

Sex of Newborns Associated With Place and Mode of Delivery: A Population-Based Study in Northern Vietnam

BackgroundThere is increasing evidence of an elevated sex ratio at birth (SRB) in many Asian countries, including Vietnam, and that this prenatal gender inequity is related to sex-selective abortion. However, few studies have investigated the relation between the sex of offspring and delivery care utilization.ObjectiveThe aim of the present study was to relate sex of newborns to place and mode of delivery in a province in northern Vietnam.MethodsA population-based surveillance system within the Neonatal Health–Knowledge Into Practice (NeoKIP) project (ISRCTN44599712) recorded all births within eight districts of Quang Ninh province in northern Vietnam from July 2008 to June 2011.ResultsIn total, there were 22,377 live births within the study area. SRB was 108 boys per 100 girls. There was a large difference in SRB depending on place of delivery, with 94 boys per 100 girls being delivered at home, whereas 113 boys per 100 girls were delivered at a district-level hospital. Cesarean section (CS) rate was 17%, and within the CS group, the SRB was 135:100.ConclusionsWe demonstrated an elevated SRB, especially at district hospital level, and that sex of offspring influenced place and mode of delivery. Although mothers to boys were more likely to receive more qualified delivery care, they were at the same time more likely to undergo unnecessary surgery. Correct information to women and family members about CS and stricter implementation of the medical indications for CS are urgently called for.     

Upsetting the balance on sex selection

It is widely assumed that the strongest case for permitting non‐medical sex selection is where parents aim at family balance. This piece criticizes one representative attempt to justify sex selection for family balance. Kluge (2007) assumes that some couples may seek sex selection because they hold discriminatory values, but this need not impugn those who merely have preferences, without evaluative commitments, for a particular sex. This is disputed by those who see any sex selection as inherently sexist because it upholds stereotypes about the sexes. This article takes an alternative approach. I argue that, even if we accept that preference‐based selection is unobjectionable, a policy permitting selection for family balancing does a poor job of distinguishing between value‐based and preference‐based selection. If we wish to permit only preference‐based sex selection we should seek to identify parents’ motives. If we wish to justify a family balancing policy, other arguments are needed.     

The relation of son preference and religion to induced abortion: the case of South Korea

This paper explores the factors that influence the practice of induced abortion in a very low fertility society, with particular emphasis on son preference and three distinct religions: Confucianism, Buddhism and Christianity. Using multivariate logistic regression models fitted by the generalized estimating equation (GEE) method, this paper analysed the data collected by the 2000 Korea National Fertility and Family Health Survey of 6348 married women aged 15-49 years with a total of 1217 pregnancy outcomes. The results showed that the likelihood of induced abortions in women with two or more children, compared with those with one child, was significantly influenced by the sex composition of the previous children: odds ratio (OR)=12.71 (95% CI=5.49, 29.42) for women with only son(s), and OR=3.91 (95% CI=1.67, 9.14) for women with only daughter(s). At parity two, women with two sons were much more likely to have induced abortions than women with two daughters (OR=5.88, 95% CI=2.70, 12.85). Although Buddhist women were not significantly different from Confucian women in induced abortion practice, Christian women were much less likely than Confucian women to have an induced abortion (OR=0.39, 95% CI=0.18, 0.88 for women with only sons and OR=0.44, 95% CI=0.24, 0.81 for women with two children). This suggests that even in this very low fertility society, son preference and religious affiliation are significant predictors of women's practice of induced abortion.     

Quantifying male attractiveness

Genetic models of sexual selection are concerned with a dynamic process in which female preference and male trait values coevolve. We present a rigorous method for characterizing evolutionary endpoints of this process in phenotypic terms. In our phenotypic characterization the mate-choice strategy of female population members determines how attractive females should find each male, and a population is evolutionarily stable if population members are actually behaving in this way. This provides a justification of phenotypic explanations of sexual selection and the insights into sexual selection that they provide. Furthermore, the phenotypic approach also has enormous advantages over a genetic approach when computing evolutionarily stable mate-choice strategies, especially when strategies are allowed to be complex time-dependent preference rules. For simplicity and clarity our analysis deals with haploid mate-choice genetics and a male trait that is inherited phenotypically, for example by vertical cultural transmission. The method is, however, easily extendible to other cases. An example illustrates that the sexy son phenomenon can occur when there is phenotypic inheritance of the male trait.     

Height development of men and women from China,South Korea,and Taiwan during the rapid economic transformation period of the 1960s–1980s

We study height trends among Chinese, South Korean, and Taiwanese groups during the rapid economic growth period of the 1960s to the 1980s. Heights rose strongly as income grew. Did rapid income growth also cause a decline in gender inequality? Or did it rise because the gains were unevenly distributed? Gender inequality is particularly interesting given the traditionally strong son preference in the region. For mainland China, we find that gender inequality was relatively modest in the pre-reform period (before the 1980s). Especially in comparison to the early 20th century, female heights grew faster than male heights. In contrast, the 1980s transition period to an economic system with market elements was characterized by increasing gender inequality in China. This was the case to an even greater extent in South Korea, where gender dimorphism noticeably increased during the 1980s, paralleling a similar increase in sex-selective abortions. Moreover, we also study other inequality patterns in the three countries, focusing on socioeconomic, regional, and educational differences between groups.     

Culture,ecology, and beliefs about gender in son preference caste groups

Ethnographers have documented the prevalence of extreme forms of female neglect and female infanticide in Tamilnadu, India, among two caste groups: Thevars (a warrior caste) and Gounders (a landowning caste). Using a cultural ecological perspective, three field studies were conducted with Thevar, Gounder, and Brahmin participants to examine caste-specific psychological antecedents to female infanticide. Studies 1 and 2 investigated son bias using resource allocation tasks. Using a culture-of-honor task, Study 3 examined the relationship between honor and son preference. In general, Gounders' son bias was related to a desire to have more sons for patrilineal transfer of ancestral land, whereas Thevars' son preference was related to honor concerns. Furthermore, the relevance of cultural ecological perspective to study female neglect is discussed.     

Sex selection in India: Why a ban is not justified

When widespread use of sex‐selective abortion and sex selection through assisted reproduction lead to severe harms to third parties and perpetuate discrimination, should these practices be banned? In this paper I focus on India and show why a common argument for a ban on sex selection fails even in these circumstances. I set aside a common objection to the argument, namely that women have a right to procreative autonomy that trumps the state's interest in protecting other parties from harm, and argue against the ban on consequentialist grounds. I perform a pairwise comparative analysis of sex selection and its plausible alternatives and argue that that the ban fails to improve the state of affairs relative to a scenario without a ban. The ban makes the situation worse, especially for mothers and their daughters. India should therefore repeal its ban on sex selection.     

Socio-demographic determinants of abortion in India: a north-South comparison

Data from the 1998-99 National Family Health Survey (NFHS2) of India are used to examine the net effects of social and demographic characteristics of women on the likelihood of abortion while emphasizing important differences between women from northern and southern states. A north-south comparison illustrates that southern women have relatively higher levels of literacy and labour force participation, lower levels of son preference, and smaller family size. Results from logistic regression analyses show that literacy, type of work, belonging to a scheduled caste or tribe, urban residence, standard of living, parity, religion, age, age at union and contraceptive behaviour all have significant effects on the likelihood of abortion. However, most of these effects significantly differ for southern and northern women. Moreover, the effects of agricultural work, son preference and age at union on the likelihood of abortion are significant for northern but not southern women.     

Cultural transmission in a demographic study of sex ratio at birth in China's future

A decline in fertility causes an increase in the sex ratio at birth (SRB) in countries with strong son preference. What happens to the SRB if fertility is maintained at a low level depends on the evolution of son preference. In this paper, we analyze trends in son preference and its effect on China's future SRB.     

‘Aching to be a boy’: A preliminary analysis of gender assignment of intersex persons in India in a culture of son preference

Intersexuality, particularly in the global South, remains an under-researched field of study. In my in-progress doctoral research project, I explore the cultural, social, and medical discourses that influence how key stakeholders such as healthcare providers make decisions about the sex and gender assignment of the intersex child in India. In this paper I interrogate some of these ideas around gender assignment of intersex people in India, paying particular attention to the context of son preference. I am interested in exploring how decisions of gender assignment by medical professionals are guided by ideas of son preference. Focusing on four qualitative, semi-structured, in-depth interviews across two cities with medical doctors from different specializations, this paper is a preliminary attempt to examine some of the factors that guide medical professionals in making decisions about gender assignment of intersex children and explore the dynamics of the decision-making process. Specifically, I explore the factors that inform doctors’ decision-making and locate these decision-making processes within the broader socio-cultural context of India.     

Does Sex-Selective Predation Stabilize or Destabilize Predator-Prey Dynamics?

Background

Little is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sex-selective harvesting and trophy hunting on long-term stability of exploited populations.

Methodology and Principal Findings

We review the quantitative evidence for sex-selective predation and study its long-term consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81 predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation on the ‘less limiting’ prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or monogamous prey requires other stabilizing mechanisms to persist.

Conclusions and Significance

Our modelling results suggest that the observed skew towards male-biased predation might reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of harvesting and trophy hunting of sexually dimorphic species.     

Does sex of children matter? Implications for fertility in Pakistan

Preference for children of either sex is considered a constraint on fertility decline as it induces many couples to keep adding on surviving children in the hope of having a desired sex composition of children. However, preferences for children of a particular sex may differ in relation to demographic and socioeconomic characteristics of women, traditional values and cultural practices, such as propagating a family name, providing economic advantages, and obtaining a medium of social and economic security in times of illness, unemployment and old age. Utilizing the Pakistan Integrated Household Survey (2001-02), this paper aims at investigating the existence of sex preference and examines sex preference differentials by different attributes of women in Pakistan. The results reveal that there is a desire to have another child in the presence of all children of one sex, either sons or daughters. The desire to have a son with only or mostly daughters, however, is stronger than the desire to have a daughter with only or mostly sons. This behaviour will retard fertility decline unless there is a shift in the desire to have children of both sexes in Pakistan.