It is argued that the author's hypothesis relating timing of insemination (and hence coital rate) to the sex ratio of the resulting children is supported by the available data on the variation of sex ratio with (1) sibship size, (2) the presence of twin sibs, and (3) parental adherence to the Jewish faith.

The prevalence of vaginal mucus at the time of ovulation was recorded by 166 women in 1800 cycles along with their basal body temperature (BBT). Seventy-five per cent of women observed mucus in every cycle, 21% in some cycles only and 4% never saw mucus. Three women conceived in cycles in which there was no mucus. The time of first appearance of mucus has been related to cycle length and to the time of rise in BBT. The implications of these findings for the use of the mucous method of avoiding conception is discussed.

After reviewing recent work indicating that the level of spontaneous fetal loss (SFL) is much higher than estimates derived from traditional sources, this paper assesses some implications of differential rates of SFL by race and maternal health and challenges the common view that early SFL is largely a function of genetic abnormalities of the fetus and thus subject to little change over time. If, as is argued here, SFL changes over time in response to changing environmental conditions, fertility trends may be affected by environmental trends. An example of the possible impact of declining SFL on marital fertility rates over the period 1940–60 in the US is provided. The paper concludes with work that uses new estimates of SFL rates to measure the extent to which induced abortion may be unnecessary because the pregnancy would terminate spontaneously, and then estimates the extent to which contraceptive failure rates, as measured in the US National Fertility Study of 1965, may be deflated due to under-reporting of SFL.

The data in this paper are drawn from interviews with a stratified probability sample of 2996 Yoruba men and women aged 17 or above living in Lagos and Western States in June–July 1973. Although drawing upon other material from the 1 ½-hour interviews the discussion concentrates upon the family size ideals of these individuals. In addition to the customary measures of ideal family size, new measures of the limits of acceptable family size are described, together with the reactions of the whole sample to a wide range of statements relating to family size and the value of children. It is shown that the smallest family which would be acceptable to any appreciable proportion of the population is four children, which would be acceptable to 18% of all respondents. Comparative data from elsewhere in the developing world are presented to show that African family size ideals are amongst the highest in the world. Age, educational and occupational differentials in perceptions of different family sizes are also discussed.

From a survey conducted in the Republic of Ireland, data are given on the opinions of 754 married women and 194 husbands regarding the Government ban on and the desired availability of contraception. Data are given stating the extent of family planning and the methods used.

An attempt has been made to determine which of several social, demographic and economic variables best account for the variance in contraceptive use in a low-income, urban Colombian population. The results indicated that of the independent variables included, occurrence or non-occurrence of intercourse in the past month, education, employment status, marital status and age were the best predictors, in that order. Altogether these factors accounted for 17% of the variance in contraceptive use and 87% of the variance within the model. The remaining variables had relatively little predictive utility; and this was particularly true for interspousal communication, race and religious commitment.

Gross motor performance data were secured from boys and girls in special education classes for the minimally brain injured. By factor analysis two gross motor factors were identified, one a strength-maturation component, and the other general motor ability. In comparison groups of educable mentally retarded children from the same school districts, the same factors were apparent, though the order of extraction was reversed.

Verbal IQs were calculated for 60 boys who had no siblings (only boys) and 64 who were the first in a sibline (first borns) at two age levels—6 and 7 years versus 11 and 12 years. In addition to a pronounced socioeconomic status (SES) effect, three of four subgroups of only boys obtained significantly higher mean IQs than first borns. These data were interpreted as supporting the view that development of verbal abilities is facilitated by contact with parental models of language behaviour, only boys benefiting from closer contact than first borns. However, interactions among IQs, age and SES suggested that although mere increased contact is adequate to foster verbal development in younger children, quality of parental stimulation is important at higher age levels.

Using data from the 1960 US census of population, migrant and non-migrant families are compared, over the period 1955–60, for family size in three residence groups of whites and non-whites. Migrant families in both colour groups are found to have a higher mean number of children under 6 years of age than do the non-migrants and a small differential is maintained even after indirect standardization for age of family head. Non-migrant families have a higher mean number of older children but this excess decreases after standardization. It is concluded that migration does not interfere with childbearing and that, on balance, migrants do not have fewer births.

A study is reported of physical growth of Jamaican schoolboys who had been admitted to hospital with severe malnutrition during infancy (index cases). Height, weight and head circumference of the index cases was compared with that of male siblings close in age (siblings), with unrelated classmates or neighbours matched for sex and age (comparisons) and with Jamaican or US growth standards. Index boys were significantly smaller in height and head circumference than comparisons and significantly smaller than sibs only in head circumference. Sibs were intermediate in stature to the index and comparison boys. When the boys were divided into three age groups there was evidence of complete catch-up in height and weight after 7 years of age, but catch-up was incomplete for head circumference in the oldest group. No significant differences in stature at follow-up of the index boys were found in relation to age when admitted to hospital.

The vicissitudes of contraceptive efforts were studied by means of personal interviews in a sample of 100 women using the outpatient facilities of a metropolitan municipal hospital.

The women were consecutive abortion repeaters, free of any mental or emotional impairment, who made genuine efforts to practise birth control. The circumstances of their failure to prevent recurrent unwanted pregnancies were analysed, and led to these conclusions.

1. The average number of birth control methods used by the subjects was 1.9, which figure does not include a resumption of a method once replaced.

2. The role of motivation is but one, and not necessarily the most essential, element in successful contraceptive practice.

3. The interplay between contraceptive technology and various elements of human behaviour puts a limit on the effectiveness of any current contraceptive method; it products a significant and irreducible number of contraceptive failures that are relatively independent of any subjective motivation.

4. As a result of such interplay, many women would temporarily suspend contraceptive practice; the subsequent activation of psychological mechanisms then makes them ignore the risk of preganancy.

Fifty years ago, in the early 1920s, Marie Stopes published her books on childbearing, contraception and sex, and immediately became famous. Indeed recently when an American jury was asked to select the 25 most influential books published in the previous 50 years, Marie Stopes was one of a list of twelve authors which included Marx, Lenin, Freud, Einstein, William James and Hitler.

I was fortunate to read her books when I began my career as a practising obstetrician in Glasgow in 1928 and I propose to discuss the changes in human reproduction which have occurred in the last 50 years under the headings of three of Marie Stopes' best known books: (1) Radiant Motherhood, (2) Planned Parenthood and (3) Married Love.

The proportion of unwanted births to married women who were delivered in a district maternity hospital during a 3-month period in 1971 was computed for each ward in the administrative area. The percentage varied from 5 to 20% with an average of 10%. These results were compared with the distributions of socio-economic variables derived from the 1971 Census. Party was shown to be the most important indicator; Kendall's rank correlation coefficient was 0·56 (P <0·01). When the effect of parity was eliminated by the use of Kendall’s partial rank correlation coefficient, overcrowding and family structure were shown to be statistically significant (P <0·05).

The Shetland Islands lie in the North Atlantic approximately equi-distant between Scotland, Norway and the Faroes. The earliest known colonizers came from the Mediterranean, but when the Vikings arrived (c. AD 800), there seem to have few or no human inhabitants. The descendants of the west Scandinavians who came to the islands in the early Viking movement still comprise the bulk of the human population, and form a series of isolates unique in the United Kingdom.

The paper summarizes the available information on the origins and physical characteristics of the Shetlanders. Much of this is trivial, but in the absence of any other review we have brought together what is known. The only blood group data are ABO frequencies which are similar to those on the other North Atlantic islands (Orkney, Faroe and Iceland). The best estimates of relationship are based on comparisons of non-metrical skull variant frequencies which show that the nearest relatives of the Shetlanders are the inhabitants of Jaeren in southern Norway. The same conclusion comes from independent evidence of linguistic affinities.

Shetland has the highest known prevalence of multiple sclerosis in the world, and possibly a high incidence of gastric ulceration. It also has a large number of standard Down's syndrome (trisomy-21) patients. These could be the result of the fathers' periodic absences at sea, resulting in their families being spread over a large span of years. Clearly there are interesting and possibly important morbidity and mortality factors operating in the population—which could give significant information about genetical factors in disease. Data on mental defect and psychiatric disease are also presented.

In a sample of 345 women aborting at a New York clinic, women having a repeat abortion had delayed significantly less in seeking abortion than had women aborting for the first time. Those having a repeat abortion were more likely to anticipate, suspect and acknowledge pregnancy, and to have located the abortion clinic more rapidly, once the decision to have an abortion was made. Psychological reactions to the decision did not differ between women having first and repeat abortions. The complex interactions of many of the factors involved in the decision-making process were examined by path analysis. Variables entering the path analysis explained 36·0 and 52·4% of the variance in delay for first and repeat abortions, respectively. The analyses suggest that women having repeat abortions come from at least three groups: (1) those whose contraceptive method failed because of technical failure; (2) those experiencing contraceptor failure due to social and personal interactions with the method not conducive to optimal contraceptive practice, and (3) those women who are not practising contraception and for whom repeated unwanted pregnancies may be a response to neurotic needs.

An analysis of Maori fertility shows that a transition from a high to a low level has begun. The crude birth rate has declined by nearly 28% during the period 1961–72; only a small part of this decline can be attributed to changes in the age–sex and marital status composition.

A substantial decline in the fertility of older women has been observed and there are indications of the beginning of a major decline in the fertility of younger women. Since women aged 30–49 still account for 30% of total fertility there is enough potential for a further fertility decline in the later child-bearing years.

Age patterns of fertility decline suggest that inter-marriage between Pakehas and Maoris is not a prime cause of the recent fertility decline. The factors which are thought to be responsible for this change in Maori fertility are rapid urbanization, a low level of infant mortality and an increase in the overall level of education.

A further decline in Maori fertility will depend on the continuation of the tendency in fertility among the younger women.