The duration of postpartum amenorrhoea was studied in a danish sample of 361 women. The median duration of amenorrhoea was 17 weeks. The 25th and 75th percentiles were 10 and 30 weeks, respectively. A significant correlation was found between the duration of postpartum amenorrhoea and of breast-feeding. However, loctation for more than 9 months did not extend the duration of amenorrhoea. Menstruation before weaning occurred in 57% of the women, and 43% terminated breast-feeding before the first menstruation. Four weeks after weaning menstruation had returned in 79% and by 8 weeks after in 93% of the mothers. At 6 months postpartum, frequency of breast-feeding, and of night-time feeding were determinants of amenorrhoea.

The genetic structure of Sicily was analysed through the distribution of surnames of 758,793 users registered in the Italian Telephone Company, corresponding to 371 communes of the island. Estimates of the coefficient of consanguinity due to random isonymy, of Fisher's a, an indicator of abundance of surnames, and of Karlin–McGregor's v, an indicator of immigration rates, were obtained for each commune. Four different estimates of genetic distance between all possible pairs of communes within each province were also obtained, and their relationship with geographic distance was studied. The logarithmic transformation of Lasker's coefficient of relationship showed correlations with the log of geographic distance which range between −0·78 and −0·40; the strongest, for the province of Catania, was attributed to the presence of Mount Etna, and the weakest, for Palermo, to the high population density of this province.

In April 1990, the prices of five brands of contraceptives in the Bangladesh social marketing project were increased, by an average of 60%. The impact on condom sales was immediate and severe, with sales for the following 12 months dropping by 46% from the average during the preceding 12 months. The effect on oral contraceptive sales was less dramatic: average sales in the year following the increases dropped slightly despite a previously established pattern of rapidly rising sales. There appears no reasonable combination of events other than the price increase itself to explain most of the difference.

This paper explores the importance of gender differences in the impact of tropical diseases on women. Malaria and schistosomiasis are used as examples but most of the observations also apply to other diseases endemic to developing countries. The distinction between sex and gender is discussed and evidence of sex and gender differences in the determinants and consequences of malaria and schistosomiasis, particularly their economic, social and personal dimensions, is reviewed. Issues on which research and intervention studies are needed are identified.

Results of a survey of some urban areas in the Pretoria–Witwatersrand–Vereenining region show differential impacts of proximate and socioeconomic factors on the fertility of urban blacks and whites. Timing of starting and ending of childbearing and the reproductive behaviour of women who have never been married account for the major differences in fertility levels. White women confine their childbearing career to the 20–39 age range, while black women utilise the entire 15–49 age range. The fertility level is quite high among black women who have never been married (in contrast to never married white women). With the exception of breast-feeding, racial patterns in other proximate determinants of fertility do not suggest the observed racial differentials in fertility.

Children's intelligence increased in the United States by approxi-mately 3 IQ points per decade over the period 1932–78. New evidence shows that these increases have been sustained during the last 20 years. Two recent studies indicate that the rates of increase for 1972–89 and 1978–89 were 3·3 and 3·5 IQ points per decade respectively.

Variation in the duration and pattern of breast-feeding contributes significantly to inter-population differences in fertility. In this paper, measures of suckling frequency and intensity are used to compare the effects of breastfeeding practices on the duration of lactational amenorrhoea, and on the length of the birth interval in three prospective studies undertaken during the 1980s, among Quechua Indians of Peru, Turkana nomads of Kenya, and Gainj of Papua New Guinea.

In all three societies, lactation is prolonged well into the second year postpartum, and frequent, on-demand breast-feeding is the norm. However, the duration of lactational amenorrhoea and the length of birth intervals vary considerably. Breast-feeding patterns among Gainj and Turkana are similar, but Turkana women resume menses some 3 months earlier than do the Gainj. The average birth interval among the Gainj exceeds that of nomadic Turkana by over 15 months. Suckling activity decreases significantly with increasing age of nurslings among both Gainj and Quechua, but not among Turkana. Earlier resumption of menses among Turkana women may be linked to the unpredictable demands of the pastoral system, which increase day-to-day variation in the number of periods of on-demand breast-feeding, although not in suckling patterns. This effect is independent of the age of infants.

The short birth intervals of Turkana women, relative to those of the Gainj, may be related to early supplementation of Turkana nurslings with butterfat and animals' milk, which reduces energetic demands on lactating women at risk of negative energy balance.

Data on patterns of consanguineous marriage were collected from 5340 families resident in eight cities in the Pakistan province of Punjab. To assess whether social and/or occupational class was interacting with con-sanguinity, information also was obtained on the hereditary qaum to which each family belonged. In the present generation 46·5% of all marriages were contracted at the level of second cousin or closer, with an average coefficient of inbreeding (F) of 0·0286, and the results indicated that in each of the seventeen qaums there was strong preference for marriage to a close biological relative. However, significant differences existed in the distribution of consanguineous marriage by qaum membership, which could interfere with the interpretation of studies into the biological effects of inbreeding.

Neonatal death (mainly due to tetanus) was common in St Kilda until 1891. Two aspects of this phenomenon are studied; factors which pre-dicted death, and the impact of neonatal death on family building. Maternal age appeared to be a predictive factor for death of the first child, but only in children of high birth order were other factors, particularly the number of previous neonatal deaths, important. The first birth interval appeared to be determined mainly by the date of the first birth, independent of neonatal mortality levels. For later intervals, the neonatal death of the previous child appeared to be the main determining factor.

Demographic data on fertility and intermarriage are useful measures of integration and assimilation. This paper reviews trends in total fertility and intermarriage of foreign populations in Europe and compares them with the trends in fertility of the host population and the sending country. In almost all cases fertility has declined. The fertility of most European immigrant populations and of some West Indian and non-Muslim Asian populations has declined to a period level at or below that of the host society. Muslim populations from Turkey, North Africa and South Asia have shown the least decline. Intermarriage is proceeding faster than might be expected in immigrant populations which seemed in economic terms to be imperfectly integrated. Up to 40% of West Indians born in the UK, for example, appear to have white partners as do high proportions of young Maghrebians in France.