A study was made of 126 new attenders at the Edinburgh FPA clinic for single women during its first year of operation. Nulliparous patients were only half as likely to have been referred from a medical source as the parous patient. The higher the social class the greater the likelihood of discussion about contraception between patient and doctor before a visit to this FPA centre. The study population was geographically very mobile. Higher social classes and students were as likely to report experience of previous sexual intercourse than others. At least 24% of patients had a very limited knowledge of contraceptive methods. Forty per cent of patients returned for a follow-up visit and older women and nulliparous women were less likely to return than others. Although most returning patients had experienced regular sexual intercourse since their first visit, 15% had not found this entirely satisfactory, and 32% had had difficulties with the prescribed method of contraception, chiefly the oral contraceptive. When compared for the same period with the city's other clinic offering contraceptive advice to single women, 24% of all attenders at both clinics had been to the FPA. The proportion of parous women at the FPA was twice that at the Brook Clinic, but Brook patients were much more likely to have already received contraceptive advice from a doctor. Discussion centres on the social-class bias in the population of attenders.

A high incidence of multiple births has been reported in an area of New Britain where there is no evidence that birth control is practised. Analysis failed to confirm Edwards' observation that the average size of the sibship after birth of twins varies with the sex of the twins. Repeated twinning occurred in 14% of women who had given birth to twins. No significant differences were found in birth intervals before and after twins but mothers of twins were more fertile, judged by the total number of pregnancies, than comparable women without twins. Mortality was greater among the twins than among the singletons and was greater among females than among males. The development of health services in the area has reduced mortality significantly.

A study was made of twinning rates in mothers of different ethnic origin delivered in two hospitals in Ibadan, Nigeria; the great majority were of Western Nigerian origin. The twinning rates in mothers of Western, Eastern, Mid-Western and Northern Nigerian origin were 45, 45, 31 and 21/1000 maternities, respectively. The monozygotic twinning rates determined by sex, placentation, blood groups and other genetically determined markers in the different ethnic groups varied very little, the differences in the overall twinning rates being mainly due to variation in the dizygotic rates. The effect of factors such as hospital selection and maternal age and parity on the observed incidence of twinning is discussed.

Daily records are the only acceptable basis for determining human coital rates. A re-analysis of such data presented by earlier writers and a study of new data suggest that within the intermenstruum (viz. the days on which there is no bleeding) the rate of coitus is highest immediately after menstruation ceases, declines thereafter and is lowest (within the intermenstruum) just before menstruation recurs.

It is not clear whether there is a minor peak around ovulation time, but such a correlation, if it exists, is certainly not very powerful.

The major cause of the higher coital rate after menstruation could be abstinence during menstruation and a post-menstrual feeling of release on the part of the woman.

The fact that coital rates are largely independent of the time of ovulation might be due to their being largely determined by the male. In any case, it provides evidence for Morris's view that human sexuality has important evolutionary functions other than reproduction.

Since 1939 Sweden has had legislation regulating the legal termination of pregnancy, and up to now more than 100,000 such operations have been performed in accordance with this legislation. Official statistics and investigations by individual researchers have provided a large amount of material, which implies a pragmatic approach to the difficult and many-sided problem of abortion, and which makes empirical evaluations of different aspects possible.

Isolation of human populations, leading to genetic divergence, is well documented in island settlements and religious isolates. Demonstration or measurement of isolation is more difficult in mainstream populations. An attempt has been made to assess such isolation by simple methods of aggregate analysis from readily available data. The limitations of the data and methods of analysis are fully appreciated, but it seems that differences between areas are detectable. Hence the methods, simple as they are, warrant further application to other communities. The analyses, both of surnames and of marriage movement data, indicate limited gene flow in Northumberland in the 18th century. Such gene flow as did occur came mainly from neighbouring communities, and there was very little long-distance inflow. There was thus a high degree of population constancy and localization in Northumberland in the 18th century. This could well be a contributory factor promoting the known genetic variability of the area.

A study was made of the return of spontaneous menstruation and fertility in 121 Thai women who had received contraceptive injections of medroxyprogesterone acetate (DMPA) at intervals of 3 or 6 months with supplements of oral oestrogen at monthly intervals and who, for various reasons, had discontinued medication after 6 months or more.

Spontanecous menstruation returned in 113 of the women within 6 months, but no direct relation was found between the number of injections, period of usage or total dose of DMPA and the time required for the return of menstruation.

Of the 121 women who discontinued medication, only seventeen stated that they did so because they wished to conceive. Of these, twelve became pregnant within 10 months and three more within 27 months. The 104 women who discontinued medication for other reasons had a much lower pregnancy rate and must be supposed to have used, at least to some extent, other methods of contraception.

Human pregnancy wastage is probably of the order of 50%. It is greatest in the earliest weeks of conception when there is a close correlation with defective embryogenesis, approximating to 100% in the first 3 weeks.

Approximately 36% of all clinically recognized abortuses have a chromosome anomaly. This figure does not represent the primary incidence of heteroploidy at conception, because it excludes pre-implantation and early implanted losses which are not recognized clinically.

This heteroploidy is most common in early pregnancy at the time when pregnancy wastage is highest. It is not a homogeneous problem but involves a wider range of chromosome anomalies than those found in the adult, autosomal trisomies, XO monosomy and triploidy being the most common findings.

It follows that errors in gametogenesis, fertilization and early cleavage divisions are a major cause of prenatal mortality. Biological factors which predispose to these faults include maternal ageing, pre-ovulatory and post-ovulatory ageing of the oocyte and ageing of the spermatozoon. Parental chromosome rearrangements are of minor importance as a cause of chromosome anomalies in abortuses, although they may be of greater significance in recurrent abortions.