Pedigree structures of 161 uncle/niece-aunt/nephew and 4420 first cousin consanguineous marriages registered during the 19th and 20th centuries in two large and very different Spanish regions have been analysed and their genetic consequences evaluated. The frequencies of the different pedigree subtypes within each degree of relationship were quite similar in both populations despite significant heterogeneity in inbreeding patterns. The mean X-linked inbreeding coefficient (Fx) for each type of cousin mating was calculated and compared to that expected for autosomal genes (F). The effect of genealogical structure on the Fx/F radio was compared to different cultural populations worldwide. Preferentiality and avoidance of close consanguinity along with specific types of pedigrees are discussed on the basis of premarital migration and sociocultural rules still deeply rooted in certain human groups. By admitting that the observed Fx coefficient is usually higher than F in most human populations some remarks have been made in terms of population genetic risk.

To examine the effects of birth spacing on early childhood mortality, 3729 singleton births in 1983–84 were followed for 3 years in rural Bangladesh. Logistic regression analyses were used to assess whether the survival of older siblings modifies the effect of preceding birth intervals and to see if the effects of preceding and succeeding birth intervals are inter-related, controlling for the effects of sex of the child, mother's age and household economic status. With the exception of the neonatal period, birth spacing effects were highly significant. A preceding birth interval of <15 months was associated with a greater mortality risk in the post-neonatal period for children with an older sibling who survived infancy. However, a short preceding birth interval did not adversely affect post-neonatal mortality if the older sibling died in infancy. Neonatal and post-neonatal deaths were higher if older siblings had died in respective age intervals. A pregnancy interval of <12 months after childbirth raised the risk of death at ages 1–2 years considerably if the child was born after a short birth interval (<15 months). The results suggest that the high mortality risks of closely spaced children are due to sibling competition for parental resources.

A sample of 104 British parents with criminal convictions had an average fertility of 3·91 children as compared with 2·21 for the general population. The result suggests that fertility for criminal behaviour is dysgenic involving an increase in the genes underlying criminal behaviour in the population.

This ecological study examines trends in socioeconomic differentials in mortality in New South Wales, Australia, over a 20-year period (1970–89). The proportion unskilled was used as the indicator of socioeconomic status and its selection justified. Using census data aggregated by Local Government Area, the relationship between mortality and socioeconomic status was examined using quintiles based on the proportion unskilled in the population. Local Government Areas were also sorted into quintiles using mortality rates (0–74 years) to describe change in mortality differentials over time. Socioeconomic differentials were more evident in the relatively homogeneous Local Government Areas within the Sydney Statistical Division than in the remaining NSW Statistical Divisions which are more heterogeneous and predominantly rural. Although there has been an overall decline in mortality for males and females, and for high and low status groups, over this period the relative socioeconomic differentials have not declined. For the most recent period (1985–89) there appears to be some widening of differentials for males. The NSW state trends are generally similar to those reported for Britain and for other industrialised countries, suggesting that this is a common trend and that policies to reduce inequalities have not been effective.

Record linking provided information on the complete reproductive schedules of a sample of 1102 couples with at least two children born alive from a rural Spanish community characterised by very high extramarital reproduction. Birth spacing was analysed considering final family size as well as the legitimate–illegitimate status and sex of the newborn, and survival of the preceding sibling.

A prospective study of 113 children in rural Bhutan registered their morbidity and weight and their mothers' subsequent pregnancies, monthly for 32 months during the children's first 3 years of life. Children whose mothers had a subsequent birth interval of 18–30 months had an incidence of diarrhoea during the subsequent pregnancy 50% higher than their matched cohort whose mothers did not become pregnant (p=0·02). The relative risk for diarrhoea calculated from pooled child months was 1·51. Children whose mothers became pregnant also tended to have a higher incidence of skin infections.

Children, whose mothers were pregnant when they terminated breastfeeding, experienced an increased incidence of diarrhoea around weaning (p=0·01). Children weaned at the same age from non-pregnant mothers did not show increased morbidity.

This study, for the first time, relates observations of children's morbidity directly in time to the occurrence of the mother's subsequent pregnancy, and provides evidence of a causal relationship between a moderately short subsequent birth interval and a concurrent increase in morbidity for the study child.

In populations in which the frequency of illegitimacy is high, illegitimates and legitimates may be subjected to different demographic and social pressures, with social and genetic consequences. A rural population from north-east Portugal is studied and variables from birth, marriage and death records are compared according to the legitimacy of the individuals. The analysis shows important differential demographic patterns in infant and child mortality and in migration prior to and related to marriage, especially in women. Some changes over time and gender differences are also evident.

Using responses from questions about age at first sexual intercourse and age at first marriage, this paper offers a method of studying premarital sexual behaviour in societies where the subject is a taboo topic. More than half of the currently married women in Kinshasa engaged in sexual intercourse before marriage. The likelihood of having premarital intercourse increases among younger women, those with higher education, and those whose ethnic groups have liberal attitudes towards sexual conduct. The results also suggest that sexual activity accounts for late marriage.

The relationship between sleep habits and psychosomatic health complaints was investigated by a questionnaire study in 148 bank workers in Tokyo. Daily bedtime was more flexible than daily rising time, and both mean bedtime and rising time tended to be earlier with increasing age. Multiple logistic regression analysis showed that psychosomatic health complaints of sleep disturbances, fatigue, digestive troubles, and depressive mood were significantly associated with sleep habits and perceived mental stress.

This paper conceptualises the motive force behind human childbearing as originating in two broad traits which have biological bases, are shaped by experiences during early life and are expressed through their effect on desires and intentions. An instrument for measuring childbearing motivation, the Childbearing Questionnaire (CBQ), is presented. Using a sample of 401 married couples two main scales, nine subscales, and several independent items are described. Evidence for the reliability and validity of this instrument is presented. The versatility of the CBQ as a research instrument and the usefulness of the conceptualisation from which it is derived as a way of integrating social, behavioural, and biological science approaches to childbearing motivation are discussed.