The maternal immune hypothesis (MIH) argues same sex attraction (SSA) results from maternal immune attack on fetal male-specific brain structures and involves the previous biological influence of elder brothers. One of the surveys supporting this is shown to be based on an unsuitable sample and to contain some strong contrary evidence. The hypothesis relies on at least four speculative ideas and there is evidence against each. (1) Likely immune response prevalence is too low compared with calculated SSA prevalence resulting from the fraternal birth order effect. (2) Testis immune attack would be more likely than brain attack but is not known. (3) Fetal brain structures are practically indistinguishable at birth and subsequent brain anatomical gender differentiation only occurs after birth when no attack is occurring. (4) The hypothesis also predicts unfavourable biology for late birth-order males but in fact the reverse is generally true, and neurological effects are very minor. Studies show aborted fetuses caused by likely maternal immune attack are predominantly girls rather than boys, which also argues against the theory. Studies on identical twins show that common factors such as uterine environment are only a small influence on SSA and post-natal idiosyncratic reactions and non-shared environmental factors are much larger influences.

In this study it is hypothesized that taller individuals are more likely to move up the scale of educational attainment compared with shorter individuals from the same social background. Three national cohorts of 19-year-old males were considered: 29,464 born in 1967 and surveyed in 1986, 31,062 born in 1976 and surveyed in 1995, and 30,851 born in 1982 and surveyed in 2001. Four social variables were used to describe the social background of each conscript in the three surveys: degree of urbanization, family size, and parental and maternal educational status. The educational status of each conscript was classified into two groups: (1) those who were secondary school students or graduates, or who had entered college, and (2) those who had completed their education at the primary school level or who had gone to a basic trade school. Multiple binomial logistic regressions were used to estimate the relative risk of achieving higher educational status by 19-year-old males relative to height and the four social factors. Consistently across the three cohorts the odd ratios (ORs) indicate that height exerts an independent and significant effect on the attained level of education at the age of 19 years in males (1986: OR=1·24, p<0·001; 1995: OR=1·24, p<0·001; 2001: OR=1·20, p<0·001). Two possible, not mutually exclusive, selective mechanisms are postulated and discussed: ‘passive’ and ‘active’ action.

This paper considers whether sex composition of existing children in Australian families is an important factor in parity progression. Using census data from 1981, 1986, 1991, 1996 and 2001, women are linked with their co-resident children, allowing investigation of family sex composition and its changing impact over time on the propensity to have another child. The study finds that parents are much more likely to have a third and fourth birth if existing children are all of the same sex, indicating a strong preference for children of both sexes. This increased propensity has added around three per cent to the fertility of recent cohorts. The paper concludes with a discussion of the potential impact of sex-selection technologies on fertility. The authors argue that future widespread use of reliable sex-selection technologies might act to increase fertility in the short term, but would lead to a long-term reduction in fertility.

The aim of this study was to evaluate the sexual attitudes and behaviours of university students. An anonymous questionnaire was administered to 550 final-year university students aged 20–25 years in Izmir, Turkey. Male students opposed premarital sexual intercourse for both genders more than female students did. The frequency of sexual intercourse among male students (61·2%) was higher than that among female students (18·3%). The mean age of first sexual intercourse was lower among male than among female respondents. The rate of condom use at first sexual intercourse was 47·4%. The frequency of having two or more past sexual partners and masturbation was higher among males than females. It was found that there were culture-specific and gender-dependent differences in sexual attitudes and behaviours of the university students. These results may help in the planning of education and health policies in Turkey.

Using pooled children data from the 1998 and 2003 Ghana Demographic and Health Surveys, this study examines religious differences in child survival in Ghana. Guided by the particularized theology and selectivity theses, a piecewise constant hazard model with gamma-shared frailty is used to explore if there are denominational differences in child mortality, and whether these could be explained through other characteristics. At the bivariate level, children whose mothers identified as Muslim and Traditional were found to have a significantly higher risk of death compared with their counterparts whose mothers identified as Christians. In the multivariate models, however, the religious differences disappeared after the mediating and confounding influence of socioeconomic factors were controlled. The findings provide support for the selectivity hypothesis, which is based on the notion that religious variations mainly reflect differential access to social and human capital rather than religious theology per se.

A fundamental public health strategy to reduce the risk of HIV/AIDS is to increase levels of awareness and knowledge about the disease. Although knowledge about HIV/AIDS and protective sexual behaviour are linked theoretically, relatively little is known about their empirical relationship. Using Demographic and Health Survey data from 23 low- and middle-income countries, this study used multilevel logistic regression models: to examine cross-national variability in the relationship between HIV/AIDS knowledge and protective behaviour (condom use and restricted sex); to investigate the moderating influences of women’s educational attainment on this relationship; and to test the extent to which severity of the HIV/AIDS epidemic accounts for cross-national variability in the association between HIV/AIDS knowledge and protective behaviour. There was an association between increased knowledge of HIV/AIDS and condom use that varied in strength and form cross-nationally. This cross-national variation was accounted for partially by the socioeconomic characteristics of women resident in the study countries and between-country differences in the severity of the HIV epidemic. While education modified the association between HIV/AIDS knowledge and protective behaviour – stronger associations at lower levels of education – epidemic severity exerted a stronger influence on behaviour than any other characteristic. Finally, this study indicates that protective sexual practices are disturbingly low. In eight of 23 countries, overall levels of condom use to prevent STDs and HIV/AIDS were less than 5·0%. Waiting for the spread of HIV/AIDS infection to change sexual practices in low- and middle-income countries will result in dramatic unnecessary suffering.

Bangladesh society is profoundly gender stratified, and yet male roles in reproductive health processes have not been rigorously investigated. This study examines the association between men’s reproductive health knowledge, attitude and behaviour and their wives’ subsequent reproductive behaviour using longitudinal data from the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B). A total of 4969 matched husband-and-wife data from a 1998 survey and women’s contraceptive use history data following this survey are used. Results show a significant association between husbands’ fertility preferences and current use of any family planning method. When wives’ background characteristics, and husbands’ background and socioeconomic characteristics are controlled for, the predicted probability of using a method of contraception among non-educated wives whose husbands want more children is 0·49 compared with 0·64 for those whose husbands do not want more children. However, the net effect of husbands’ preference for additional children diminishes as wives’ level of education increases. Among wives who had completed high school, the predicted probability of using a method of contraception is 0·70 for those whose husbands want more children compared with 0·69 for those whose husbands do not want more children.

The associations between household demographic variables and mortality of children aged less than five years were investigated using data from the 1998 Demographic and Health Survey (DHS) of the Republic of Côte d’Ivoire, Western Africa. Of the total of 1992 children born to women included in the study population during the 5-year period preceding the survey, 260 (13%) had died and 1732 (87%) were alive at the time of the survey. Logistic regression analyses used to compare biosocial variables between the deceased and living children showed that the sex of the child, birth interval and mother’s occupation were associated with child’s survival status. After adjusting for their effects, household demographic variables (i.e. number of household members, number of household members under 5 years [HM−5Y], number of household members 5 years or older [HM+5Y], the proportion of HM−5Y among all household members, and the ratio of HM−5Y to HM+5Y) were shown to be associated with the child’s survival status. This study provided insight into the effects of intra-household competition among children and availability of care-givers as potential determinants of child survival. The results indicate that improvement of the childcare environment and reproductive intervention are necessary to reduce child mortality in West African countries.

A characteristic of African pre-transitional fertility regimes is large ideal family size. This has been used to support claims of cultural entrenchment of high fertility. Yet in Kenya fertility rates have fallen. In this paper this fall is explored in relation to trends in fertility norms and attitudes using four sequential cross-sectional surveys spanning the fertility transition in Kenya (1978, 1984, 1989 and 1998). The most rapid fall in the reported ideal family size occurred between 1984 and 1989, whilst the most rapid fall in the total fertility rate occurred 5 to 10 years later, between 1989 and 1998. Thus these data, spanning the fertility transition in Kenya, support the traditional demographic model that demand for fertility limitation drives fertility decline. These data also suggest that the decline in fertility norms over time was partly a period effect, as the reported ideal family size was seen to fall simultaneously in all age cohorts, and partly a cohort effect, as older age cohorts reporting higher ideal family sizes were replaced by younger cohorts reporting lower ideal family sizes. These data also suggest that a new fertility norm of four children may have developed by 1989 and continued until 1998. This is consistent with, and perhaps could have been used to predict, the stall in the Kenyan fertility decline after 1998.

Greater female autonomy is mirrored through better performance in the major demographic and social indicators. This study attempts to capture the effect of religion on the status of women considering ‘Greater Bengal’. There is much evidence suggesting that when cultural factors are constant, religion does not have a significant effect on any demographic issue. In this paper, the validity of this proposition is examined using two datasets, namely NFHS II (98–99) and BDHS 2000. It is clear from the analyses that not only region but also religion has a distinct effect on the status of women. In West Bengal, the religious gap for all the indicators considered is pretty high, whereas in Bangladesh the gap is not that wide. A state-level population policy is needed in West Bengal to act as a social leveller.

In fertility surveys often women (and sometimes men) are asked their fertility desires, i.e. whether they want a/nother birth or not. Some respond that they are undecided. This study examines whether these persons are more like those who say they want more births or like those who say they want no more births. Data on married men and women in 29 Demographic and Health Surveys with sample sizes ranging from 300 to 3000 are used. A logistic regression equation is estimated within each country for those with known desires and then used to classify each person who was undecided. In all sub-Saharan African countries (n=20) and for both sexes, 50% or more of the undecided persons are classified as wanting more children (with one exception of wives in Kenya). By contrast in all five Latin American countries for both sexes less than 50% of the undecided were classified in the ‘want more’ group (with an exception of husbands in the Dominican Republic). Generally, the undecided tend to be classified the same as the majority among those in the survey with stated desires.

The second-to-fourth digit ratio (2D:4D) presents an anatomical sex difference in humans. On average, men tend to have lower 2D:4D compared with women. There is fairly strong evidence for a role of the 2D:4D ratio as a biomarker for the organizational (permanent) effects of prenatal testosterone on the brain and behaviour. Recently, an accumulating research programme has shown 2D:4D to be related to a multitude of sex-dependent, hormonally influenced biosocial traits and phenotypes which reach into the domains of ability, behaviour, fertility, health, personality and sexuality. This study investigated the degree of assortative mating (spousal similarity) in a sample of 239 native Austrian couples of parental or grandparental age, all of them having reproduced. Results included: (i) significant spousal correlations of +0·19 and +0·18 for right-hand and left-hand 2D:4D, respectively, and +0·24 for average 2D:4D; (ii) no assortative mating effect on the right-minus-left difference in 2D:4D; (iii) indications consistent with a possible generational decrease of spousal similarity in 2D:4D; (iv) a prevalence of couples with a lower right-hand 2D:4D observed in the husband compared with his wife; and (v) relations of spousal 2D:4D patterns to spousal age differences, such that matings of men with more male-typical trait expressions (namely, a generally low right-hand 2D:4D or showing a lower right-minus-left 2D:4D difference than their wives) implicated larger male-minus-female age differences, i.e. younger wives. It is argued that assortative mating on 2D:4D operates indirectly and may be mediated through the assortment on other, more perceptible, physical traits and psychological phenotypes that entertain associations with 2D:4D and are relevant for courtship and mate choice.

This paper reviews various theoretical approaches towards an explanation of parental gender preferences and empirical findings from developing as well as from industrialized countries, focusing on the role of gender preferences in reproductive decisions. Although various attempts have been made to shed light on the mechanisms underlying the observed patterns of sex preferences for children, a fully satisfying theoretical explanation is still not at hand. Empirically, a distinct and stable preference for at least one child of each sex can be observed as a common pattern of parental sex preferences across many different social, economic and cultural contexts. Further – and ideally multidisciplinary – research that helps to improve our understanding of this phenomenon is highly desirable.

Based on national data from civil birth registration systems, this paper provides an overview of trends in the twinning birth rates in fifteen developed countries. Patterns and differentials in such rates across populations are described, and trends over time are given. The evolution of the twinning rate in industrialized countries over the last century follows broadly the same pattern. One exception is the period around World War I, with a peak in the twinning rate being observed during the war, or just after it, although this was not registered in all countries. Since the mid-1970s twinning rates have increased in many developed countries in response to a growing use of fertility-stimulating treatments such as in vitro fertilization.

This study uses the 1996 Census and the 1998 Demographic and Health Survey (DHS) to investigate the level of and trend in infant and child mortality and their covariates in South Africa. Census estimates of childhood mortality are higher than those from the DHS. Analysis suggests that the former overestimate mortality while the latter are probably slightly too low. Both inquiries document a reversal of the trend toward lower mortality in the 1990s. Under-five mortality increased by about a third during the five years up to early 1998. By then the infant mortality rate was about 55 per 1000 and under-five mortality 72 per 1000. Other factors may explain the tapering off of the decline in mortality after the late 1980s but AIDS deaths account for its increase. Inequalities in childhood mortality between population groups, rooted in past discriminatory apartheid policies, shrank between the late-1970s and mid-1990s. However, they remain substantial and are largely unaccounted for by province, metropolitan residence and inter-group differences in mothers’ education. The HIV/AIDS epidemic is likely to offset the beneficial impact of post-apartheid pro-poor policies and may exacerbate racial differences in childhood mortality in South Africa. There is an urgent need to improve the routine collection of statistics to monitor child mortality so as to assess progress towards the Millennium Development Goals and track inequalities.

There is evidence that ‘health life expectancy’ (expected number of years to be lived in health) differs by socioeconomic status. Time spent in health or disability plays a critical role in the use of health care services. The objective of this study was to estimate ‘disability life expectancy’ by age, gender and education attainment for the elderly of the city of São Paulo, Brazil, in the year 2000. Data came from the SABE database, population censuses and mortality statistics (SEADE Foundation). Life expectancy with disability was calculated using Sullivan’s method on the basis of the current probability of death and prevalence of disability by educational level. The prevalence of disability increased with age, for both sexes and both levels of educational attainment studied. Men showed a lower prevalence of disability, in general, and persons with lower educational attainment showed a higher prevalence of disability. Regarding life expectancy, women could expect to live longer than men, with and without disability. For both sexes, the percentage of life expectancy lived with disability decreased with increasing educational attainment. With increasing educational attainment, the sex differences in the percentage of remaining years to be lived with disability increased for most ages. Finally, the percentage of remaining years to be lived with disability increased with age for males and females, except for males with high educational attainment between the ages 70–75 and 75–80. The results may serve as a guide for public policies in the country, since health problems faced by older persons, such as disability, are the result of a number of past experiences during their life-times, such as health care, housing conditions, hygiene practices and education. Education influences health behaviours and is related, to some extent, to all these factors. Therefore, improvements in education for the disadvantaged may improve health.

This study examines the reproductive success of men and women in rural Ethiopia as a function of their marital status, specifically by comparing polygamously and monogamously married individuals. In line with predictions from evolutionary theory, polygamy is beneficial to male reproductive success (i.e. producing larger numbers of surviving offspring). The success of polygamously married females depends on wife rank: the first wives of polygamous husbands do better than monogamously married women and much better than second or third wives. These effects are mirrored in child nutritional status: the children of second and third wives have lower weight for height. Due to potential, largely unmeasurable differences in marriageability (quality) between individuals, it was not possible to support a model of either resource-holding polygyny combined with female choice or female coercion into unwanted marriages. First wives of polygamously married men marry at a younger age and attract a higher brideprice, suggesting that both the males and females in the marriage are likely to be of higher quality (due to wealth, family status or some other factor such as beauty). Unions that end up monogamous are likely to be between slightly lower quality individuals; and second and third wives, who marry at the oldest ages and attract the lowest brideprice, may be ‘making the best of a bad job’. The relatively long gap between first and second marriages may mean that first wives of highly marriageable males can enjoy considerable reproductive success before their husbands marry again.

While a country’s health policy aims to provide health services to all who need them, very little in known about unmet need for additional medical care from users’ perspectives in Bangladesh. This study examined unmet medical need (defined as whether a mother felt that, to manage sickness, her child had required medical care that was not available, regardless of reasons and medical care sought) of 2123 under-15 sick children by illness and child’s socioeconomic characteristics in rural Bangladesh. The 1996 Health and Socioeconomic Survey conducted in Matlab recorded children’s chronic (a disease or a condition lasting 3 months or more) and acute (a disease or a condition with a rapid onset and a short, severe course) morbidity, medical care sought to combat illness and unmet needs for additional medical services in mothers’ views to manage the illness. The survey also recorded household socioeconomic data. Logistic regression was used to examine the data. The results reveal that unmet needs for additional medical care were 5·4% for children with acute illnesses, and 30·2% for children with chronic illnesses. For chronic illnesses, seeking medical care to manage illness from any health provider outside the home reduced unmet medical needs. Economic inequalities existed for both acute and chronic illnesses: the odds ratio of unmet medical needs for sick children of the least poor households was 0·42 (95% CI: 0·28–0·64) times that for sick children of the very poor households. The critically high unmet needs for children’s chronic morbidity reveal that the chronic disease control programme in Bangladesh needs urgent revisiting and strengthening.