The relationship between breast-feeding and subsequent pregnancy in East Bhutan is examined, against the background of local attitudes to family planning. Ninety-eight mothers who had given birth 30–36 months earlier were interviewed. Semisolid supplementary feeding was introduced at a median age of 3 months. Median total duration of breast-feeding was 28 months, and day and night breast-feeding on demand was continued throughout. Median duration of postpartum amenorrhoea was 12 months, and was associated with the timing of the introduction of supplementary foods.

There was a significant association between the occurrence of a subsequent pregnancy and early termination of breast-feeding. The relationships between breast-feeding pattern and pregnancy interval are complex, and their relative influence changes with time. During the first year postpartum, infertility during lactational amenorrhoea is important. During the second year there is a strong negative effect on lactation from the next pregnancy. The only important reason for ceasing to breast-feed within 2 years seems to be a new pregnancy.

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.

The hypothesis that psychological stress during early childhood leads to advanced reproductive maturation was assessed using data from the California Childhood Health and Development Study. Regression analyses failed to indicate that bed wetting, nightmares or thumb-sucking at age 5 predict age at menarche, regardless of controls for mother's age at menarche. Among socioeconomic variables suggested as contextual stressors measured at age 9–11 only mother's education was a significant predictor of daughter's age at menarche, though its effect is trivial compared to mother's age at menarche. Path analysis on a subsample of the subjects failed to demonstrate the hypothesised indirect effect of mother's age at menarche on daughter's age at menarche acting through early marriage and marital dissolution. These results cast doubt on the theory that early childhood stress is the key to divergent reproductive strategies among females based on the timing of reproductive maturation.

This analysis of the 1986 Liberia Demographic and Health Survey data finds remarkably high fertility levels among women who have never married or lived with a man, reflecting widespread pre-marital sex and a lack of use of contraception. It is found that single Liberian women are more likely to foster out children than married Liberian women of the same age.

Menopause (cessation of menstruction) and the period surrounding it (climacterium) are often defined retrospectively by asking a woman the date of her last menstrual period (LMP). Based on a survey of 2000 women aged 45–64 in 1989 in Finland, this study examines (1) the relation between these definitions and women's own definitions of their climacteric status and of the cessation of menstruction and (2) the effect of menopausal and postmeno pausal hormone therapy and hysterectomy on the definition of menopause and climacterium. Agreement of the woman's own definition of her climacteric status and interval since LMP was 25% among current hormone users, 41% among hysterectomised women and 64% among those who were neither currently using hormones nor had been hysterectomised. Current hormone users defined the climacteric phase as longer than their LMP suggested. Current hormone use and hysterectomy had little effect on reported final cessation of menstrual periods. It is concluded that hysterectomy and hormone therapy shape women's thinking about the end of reproductive life, blur the concepts of menopause and postmenopause and confuse the measurement of age at menopause.

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.

Coital frequency is studied among couples as a function of marital or cohabiting status, relationship duration, number of children, religious affiliation, income, education, fertility intentions, age, race, self-assessed health, time spent in work, and perceived relationship quality. Data are from the 1987–88 National Survey of Families and Households. Predictors of coital frequency that were stable across several analyses were male's and female's ages, the duration of the relationship, and the male partner's self-assessed health. When the discrepancy in partners' reports was adjusted, cohabitation status, number of children, future fertility intentions, religious affiliation, and relationship quality as assessed by the female partner were significant. The results suggest a substantial idiosyncratic component to the determination of coital frequency in relationships.

A survey of 673 consecutive Papua New Guinean parturients at the Port Moresby General Hospital, in May and June 1990, showed that 28% had ever used a family planning (FP) method, chiefly a hormonal method (93% of ever-users). Only seventeen of 239 (7·1%) nulliparae had ever used an FP method, compared with 170 of 434 (39·2%) parous subjects. Education of mother and of husband were independently and significantly associated with FP ever-use. Seventeen (4·9%) of 347 women who had a surviving child, had not breast-fed the child. The interval between the birth of the surviving child and the start of the index pregnancy was significantly associated with the duration of breast-feeding; the longer the duration of breast-feeding, the longer the inter birth interval.

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.

The influence of ethnicity on obstetric performance in Singapore was assessed by retrospective analysis of all deliveries in the National University Hospital over a 7-year period. Malay mothers were younger, shorter, less educated, of higher parity, were more likely to have had no antenatal care, and had the highest incidence of premature labour. However, mothers of Indian origin had the smallest babies, the highest incidence of low birth weight and significantly higher perinatal mortality rates. Chinese mothers fared better than their Malay and Indian counterparts in all parameters assessed. The ethnic origin of the mother has an important bearing on perinatal performance. This emphasises the importance of designing appropriate strategies to improve perinatal health in the different ethnic groups.

Contraceptive failure was an important determinant of fertility in China in the 1980s. Based on the data from the China Two-per-Thousand Fertility Survey, this study shows that about 7% of the general fertility rate of currently married women aged 15–49 for a 12-month period is attributed to contraceptive failure, mainly due to the high failure rate associated with IUD use. A number of demographic characteristics are associated with contraceptive use, and with contraceptive failure and its outcome. Relevant socioeconomic differentials are also identified.

Age variations in the influences of three sets of proximate factors on child survival in Ondo State, Nigeria, during 1981–86 are described. Biodemographic factors covary very strongly with mortality risks during the first month of life, weakly during months 1–11, and imperceptibly beyond infancy. Microenvironmental factors progressively strongly covary with mortality after the neonatal period, while health services accessibility and care factors broadly covary strongly with mortality throughout early childhood. Patterns in the size of the hypothetical population-level impacts of these factors suggest that promoting assisted use of toilet facilities within households by under-5s and wider provision of dispensaries and hospitals would yield cost-effective and notable reductions in overall childhood mortality levels in the study setting.

Data on patterns and trends in sterilisation in Britain among women, men and couples are presented using life table approaches with data from a national survey, the General Household Survey. Among couples under age 50, sterilisation is the main method of contraception used, with slightly more women than men being sterilised, although this is reversed if only contraceptive sterilisation is considered. Trends in contraception have remained relatively constant in recent decades. Patterns of sterilisation differ following births of different orders. For example, the resort to sterilisation is much quicker after a third birth than after a second. The proportions of men and women who have been sterilised and then formed a subsequent partnership are very small, so the effect of sterilisation in preventing births in such unions is negligible.

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.

Daily behaviour patterns in a hunter–gatherer community of Colombian Indians show that individual activities are regulated by ultradian behaviour cycles of about 2 hr and that these cycles can be synchronised by social interaction. A computer model was developed which simulated an artificial community and generated dynamic portraits of locomotor activity and social aggregation similar to those of the observed community of Colombian Indians. Social phase-locking of ultradian behaviour cycles occurred, contributing to the safety of group members and their economy of effort in gathering and related activities. Social synchronisation of ultradian behaviour cycles may also have occurred in early hominid groups.

This paper compares levels and trends of population growth rates, age and sex composition, mortality, and fertility including family planning practices in the world's two most populous countries, China and India. Both countries are undergoing demographic transition but China is nearer than India to achieving a stationary population. Fertility in China has declined below replacement level while in India it is nearly one and a half children per woman above replacement level. Both countries have achieved large reductions in mortality but life expectancy at birth in China is currently about 10 years longer than in India. Both countries have young populations but China will precede India in the aging of population structure during the 21st century.

A comparative study of 1100 women aged 25–45 years, users and non-users of modern methods of contraception, in the urban centres of Lahore and Faisalabad was conducted in 1991. The objective of the study was to investigate reproductive behaviour and the extent to which social, cultural and attitudinal variables, such as beliefs and values about family life, religiosity and fatalism, influence the fertility decision-making process. Preferences for smaller families were found to be consistently associated with modern attitudes and behaviour towards family and religious values and obligations. Family income, husband's occupation and religiosity offered no explanation of reproductive behaviour. It is concluded that cultural setting and tradition exert an important influence on reproductive behaviour, independent of economic development.

Bivariate and multivariate analyses of the influence of demographic and sociocultural factors on contraceptive knowledge, attitudes and practice among currently married respondents in Uganda show that: (1) contraceptive knowledge is widespread, even among women with no education; (ii) the majority of the respondents have favourable attitudes towards contraceptive use; (iii) the level of contraceptive use is low in comparison with knowledge and attitudes. Post-primary education, ethnicity, residence, the presence of the spouse in the household and discussion of family planning with spouse were strong predictors of knowledge and favourable attitudes towards contraception. Secondary or higher education, discussion of family planning with spouse and urban residence strongly influenced contraceptive use, but child mortality did not. The use of condoms as a behavioural change to avoid contracting HIV/AIDS was low. The results suggest that, particularly in rural areas, family planning services are not meeting the needs of potential clients.

Infant and child mortality levels and trends in Bangladesh are examined using data from the 1989 Bangladesh Fertility Survey. Both infant and child mortality declined from the mid 1970s but infant mortality declined more quickly. The level of infant mortality in 1989 was around 100 per 1000 live births while child mortality (5q) was 200 per 1000 live births. Life table analysis confirms the change in infant and child mortality.

The decline in infant mortality is attributed to the introduction of improved public health measures and access to maternal and child health services.

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.