The high variability between centres in the incidence of side effects related to intrauterine devices (IUDs) is taken to indicate the need to direct research attention towards the context in which IUDs are inserted, as opposed to exclusive concern with the nature of the device. This paper considers the significance of psychological factors at the time of insertion in the light of recent studies indicating the benefits of adequate patient preparation.

The fertility of Japanese agricultural immigrants settled in eastern Bolivia was studied in comparison with Japanese populations in South Brazil and in Japan. The fertility of the Japanese in Bolivia was found to be high compared with the contemporary Japanese living in Japan, and lay between the levels for South Brazil in 1952 and for Japan in 1970. It is supposed that the Japanese immigrant women in Bolivia maintained the high level of fertility which was prevailing in Japan at the time when they had emigrated, while the level of fertility in Japan had declined remarkably.

Guerrero (1975) has cited a wealth of direct data supporting the hypothesis that timing of insemination is related to the sex of the resulting zygote. It is argued here that if this hypothesis were correct, then parental coital rate would be associated with the sex of the resulting children. It is suggested here that empirical data support this inference and hence support the hypothesis.

It is estimated that if Pmale (the probability that a zygote will be male) declines linearly across the fertile period, that decline is from about 0·57 to 0·45.

Serum prolactin has been measured in single blood samples collected within the first 22 post-partum months from 97 nursing mothers from an urban area (Bukavu) of Zaïre. Nursing mothers are hyperprolactinemic, higher serum prolactin levels being associated with more frequent suckling episodes per day. Furthermore, serum prolactin declines rapidly in mothers who are giving the breast less than four times per day: the levels are within the normal range found in non-lactating women after the 6th post-partum month. Among mothers giving the breast more than six times per day, serum prolactin does not decline significantly during the 1st post-partum year.

Previous lactation experiences do not facilitate the effect of nursing on prolactin secretion during subsequent lactations.

Many mothers in low-income countries, particularly in rural areas, nurse their children for 1–2 years on the average. The main purpose of this practice is, of course, to provide the newborn child with the nutrition necessary for its survival. Prolonged breast-feeding, however, also has a birth-spacing effect and postpones the next pregnancy by inhibiting ovulation and by delaying resumption of the menstrual cycle. Suckling of the infant is important for this suppression of the menstrual cycle because it leads to the release of prolactin, which not only plays an important role in milk production but also inhibits the release of gonadotrophins which initiate resumption of the menstrual cycle. For further details about these endocrinological aspects of lactation see, for example, Rolland et al. (1975); Thomson, Hytten & Black (1975) and Buchanan (1975).

Analysis of stillbirth data from the State of Wisconsin demonstrates that the association of stillbirth rate with mother's age is basically an artifact of analysis rather than a reflection of genuine effects of age on risk. When births to mothers of a single parity are subdivided according to the amount of education completed by the mother, the association between stillbirth rate and maternal age in each educational group differs substantially from the others. The association observed for all births of a single parity is inapplicable to any educational subdivision of the data.

It is argued that the associations which are observed are the consequence of social forces which distribute women of varying intrinsic risk of stillbirth unevenly among age–parity categories.

Questions concerning their attitudes towards induced abortion in six different circumstances were asked of 1254 rural Thai married women, aged 15–44, in a 1972 nationwide fertility survey. A positive response was given to one or more of the questions by nearly three-fifths of the women; the largest proportion of positive responses (42·0%) was given by women if the pregnancy resulted from rape, and 40·1 % responded affirmatively if the pregnancy might endanger the health of the woman. The lowest proportions, but still nearly one-fifth of the women, were in favour of abortion if the couple do not want another child or if they cannot support another child. Responses are analysed in relation to the demographic and socio-economic characteristics of the women and their husbands, to fertility and family planning experiences, and to the women's communication activities. Comparisons of the results are made with similar data from rural South Korea, rural US and suburban Thailand. The study suggests that positive attitudes towards induced abortion among Thai rural women reflect traditional values, not recent ‘modernization’ ones.

Breast-feeding in the human and higher primates unlike the case of most other mammals, is learned rather than instinctive; over a long time it has been shown to be highly labile. Its success appears to depend not only upon the capacity of the mother to lactate, i.e. to produce milk, or on the child's ability to suckle, but perhaps more significantly, on the mother's desire to breast-feed, on the availability of sufficient reference models upon which she can base her own performance and draw upon for psycho-social support during lactation. In modern settings breast-feeding is likely to involve the mother in complex and new role situations, and to become increasingly vulnerable to the social characteristics of the environment in which she operates.

The average male–female performance difference in the three sports of track athletics, swimming and time trial cycling are examined between the years 1948 and 1976. During this period females have gradually come to participate in a much larger number of events, particularly those of longer duration. In each of these three sports, women's performances in relation to men's have more or less continuously improved and it appears that if the changes between 1948 and 1976 are maintained, average female performance will equal that of males for all events currently competed in by both sexes in these sports at some time during the next century. Estimates as to when, precisely, this will occur vary somewhat according to the basis on which the calculations are made. The other main change evident during these years is that in all three sports women's performances relative to men's for events of long duration have become as good or better than their relative performance at events of short duration.

The incidence of Down syndrome in Scotland between 1960 and 1974 was estimated using data from thirteen Area Health Boards. Incidences in individual years, in different months of the year and in different maternal age groups were also determined. There was an apparent increase in incidence in more recent years almost certainly due to increased ascertainment. This may have obscured any decrease in incidence which might be expected as a result of a decrease in mean maternal age during this period and the introduction of antenatal diagnosis. No seasonal differences in incidence could be detected either in the whole area or in individual Area Health Boards. There was an increase in incidence with maternal age which was not significantly different from that found by other investigators. There was also an indication of an increase in relative incidence (% Down syndrome births/% live births) over the period 1966–74 in mothers aged 35 years and older.

This paper compares the results of questions about the best number of children and the desire for more children from three Nigerian sample surveys of adult females: in the Lagos metropolis (1973), in West Nigeria (1973), and among the Ngwa Ibo in the East Central State (1974). In Lagos and West Nigeria support for the ‘small’ family (of four children or, rarely, less) is more prevalent amongst the younger, urban bred and educated women: when these achieve their preferred family size a decline in fertility may be implemented. Among the Ngwa Ibo four children are seen as too few and the desire to stop childbearing only receives majority support from wives with seven or more surviving children. Economic constraints on family size have less impact on the Ngwa Ibo but glimmerings of interest in family limitation, albeit at high parities, are apparent among the educated Ngwa wives.

The process of urbanization in the Third World has vastly outstripped the equivalent change in industrialized countries, and also far exceeds the population growth. This urbanization has been associated with the spread of artificial feeding and associated short birth intervals. Although relatively few studies have been undertaken on the effect of length of birth interval, we have good evidence that it is associated with poorer growth, a less satisfactory intellectual development, and a higher mortality. Child health programmes have, up to the present, been only marginally involved in the question of birth interval, although as mentioned this has a considerable effect on the health of the child. In overcoming malnutrition, simple weight charts are now widely accepted as a useful tool by which the adequate growth of the child can be monitored, and in this way malnutrition prevented. These same weight charts can be a useful means of identifying in any community the month in which a woman has a 5% chance of conceiving again. The charts can also be used as a means of recording the dialogue between the health worker and the parents on the most appropriate time interval to separate their children. However, to achieve this the developing countries will need a vast increase in the health personnel they have available. Experience now in a number of countries suggests that the part-time health worker may be particularly appropriate for providing such services.

The first part of the paper traces changes in the length of the childbearing period and ages of women at the time of their first and last births among women in Australia married between 1905–09 and 1965–69. The source of information was survey data concerning the respondents themselves (once married, currently married women aged under 60 years at 1971) and information that they gave concerning their mothers' childbearing experience. The main observations are that the trend towards smaller families was more marked among the mothers and that the change in the size distribution of families was the major factor in reducing the length of the childbearing period for marriages occurring up to the Second World War, while closer spacing of children was the major factor since then. The second part of the paper examines more detailed supplementary information about the respondents, including changes in the dispersion of the timing of births, the rapid rate of childbearing among the 1955–59 marriage cohort, reasons for delaying the first birth, and differences in behaviour according to education and religion. The discussion raises the question of the rationality of the trend towards closer spacing of children, with special reference to the interaction between a woman's work role and family role.

This article considers the methods used to estimate the number of abortions before the 1967 Abortion Act came into operation. It suggests that the registration of legal abortions has enabled a new method to be used to calculate the number of illegal operations. The article concludes that the major effect of the Act was to transfer abortions from the illegal to the legal sector and, using the new method of calculation, estimates a total number of abortions immediately before the Act of just over 100,000 a year.

The study demonstrates that, regardless of location, a pronounced reduction in fertility is achieved in Sri Lanka by the completion of junior secondary or higher levels of education; the reduction seems to be more marked in rural than in urban areas. Increased efforts to ensure that a significantly higher proportion of girls in Sri Lanka complete at least the junior secondary level would be likely to effect a significant reduction in fertility. It is therefore important in developing countries to explore the potential influence of female educational attainment as an effective weapon towards fertility reduction and to ascertain the extent of the decline in fertility produced by varing degrees of education, according to various characteristics.

Data were collected from 1044 mothers resident in the rural areas of Zambia during a National Nutrition Status Survey, to determine the effect of lactation on the interval between conceptions. Lactation is very prolonged with a small proportion of mothers continuing up to 33 months. A main reason for cessation of breast-feeding appears to be a new pregnancy, only 1.5% of mothers being neither pregnant nor lactating up to 12 months. During lactation, conception is delayed for at least 12 months. The peak in new conceptions occurs between 25 and 27 months. The normal interval between births is 3 years for rural Zambian mothers.

The decline in the number of legitimate live births in England and Wales from the peak in 1964 has been partitioned into components due to changes in fertility rates, components due to changes in the composition of the population exposed to risk, and an interaction component. Fertility rates specific for age of mother at birth of child, duration of marriage, parity and age of mother at marriage were considered but in all cases it was found that the decline was not as great as the change in fertility rates implied. This was due to increases in the number of births due to changes in the composition of the population exposed to risk.

The decline in the number of births due to changes in fertility rates specific for age of mother/duration of marriage/parity/age at marriage has been expressed as a percentage of the number of births to each specific group and it was found that generally the percentage decline became greater as age of mother/duration of marriage/parity/age at marriage increased. However this did not apply for the youngest age groups, the shortest durations of marriage, the youngest ages at marriage and the lowest parity. This result needs further investigation. Is this evidence of a deferment of births by young mothers (with short durations, low parities and young ages at marriage)? Alternatively, is this evidence of the beginning of a really significant and widespread change of attitude to family size?

Oestrogens as postcoital contraception have been prescribed for 282 women at the Brook Advisory Centre (Avon) since January 1973. A daily dose of 50 mg diethylstilboestrol for 5 days started within 72 hr of unprotected intercourse was used from January 1973. This was changed to 5 mg ethinyl oestradiol in May 1974. There were no pregnancies nor any serious side effects. Follow-up showed that most women had their next period at the expected time.

A survey was carried out on 108 Chilean children and a selection of their families. The factors studied were: (1) social, (2) demographic and dietary—to provide a background to the study, (3) nutrition—to assess the incidence and degree of malnutrition and (4) haematology—to determine the incidence of anaemia.

The major findings which have emerged are: (1) the diet of the people was not severely impaired, but it was observed that only small quantities of food with high nutritive value were consumed; (2) undernutrition was present with 41·5% of the children having first degree, 11·4% second degree and 1·0% third degree malnutrition (Gomez classification); (3) 46·1% of the children were anaemic, apparently because of iron deficiency.

The concluding discussion centres on some constructive suggestions for improvement of existing conditions leading to better standards of health.

It is generally acknowledged that the popularity of breast-feeding, expressed in terms of the frequency with which it is taken up, and the length of time it is continued, is declining, and that, especially among populations of the Third World, the implications of this decline for infant health are likely to be serious and far reaching.