The length of the post-ovulatory phase in a composite sample of menstrual cycles increases linearly with cycle length until cycle length reaches about 30 days, but thereafter it ceases to increase (Vollman, 1953; Bailey & Marshall, 1970). By contrast, plotted against the mean cycle length of the individual, the length of the post-ovulatory phase continues to increase roughly linearly with mean cycle length. It is concluded (a) that many long cycles are aberrant occurrences among cycles of normal length and are due to lengthening of the pre-ovulatory phase and (b) that where the mean cycle length is long, ovulation, as in shorter cycles, occurs just before the middle of the cycle, so that the post-ovulatory phase is longer than usual.

The most fertile day seems to be the one before mid-cycle. These conclusions are the basis for the following formula for calendar rhythm:

If x is the shortest and y the longest cycle in a woman's menstrual record, the ‘unsafe’ days start on Day (½x − 5) and last for (y − x + 8) days.

The object of the study was to make an objective assessment of the validity of ascertaining personality from handwriting. The subjects chosen for the research were twenty-four pairs of identical and twenty-four pairs of non-identical twins. Personality scores were obtained from each subject, and each pair of twins was rated by their parent(s) on a questionnaire comparing their personality and development. These ratings were compared with ratings of within-pair personality differences based on the examination of samples of handwriting by a consultant graphologist and by a team of eight amateurs. The results showed that handwriting is not likely to be helpful in the study of neuroticism and is of no value in the determination of zygosity. In the case of extraversion, however, the correlations were low but in the expected direction and with reasonably good internal consistency.

The milk yield in a group of lactating Egyptian women was estimated during the first twelve post-partum months. It increased from the second to the seventh month, then dropped gradually in the last four months. The best milk yield was found in women aged 20–30 years, with a parity of two to four and an inter-delivery interval of 30–36 months. (Summary in Arabic, p. 401.)

The composition of human milk during the first year of lactation was studied. The effect of age, parity and the length of inter-delivery interval on the composition is described. Of the three parameters, the length of inter-delivery intervals was the most important, while the other two were weakly correlated. (Summary in Arabic, p. 409.)

The sample under consideration in this study was composed of 3445 women who accepted some method of pregnancy prevention after consultation with the National Family Planning organization in the Republic of the Philippines. Subjects were divided into four groups: those women who used an oral contraceptive, women using the IUD, women practising the rhythm method, and those who relied on other methods of birth control.

This study attempted to reveal sources of information on family planning and reasons for acceptance of a birth control method, as well as the woman's actual and ideal family size and the interval since her last pregnancy. In addition, the relationship between the woman's educational level and the type of technique selected and husband's occupation as a correlate of the method chosen were also investigated.

The findings appear to suggest, among other things, that women near the end of the child-bearing years were less likely to select one of the more effective methods. Women with large families and those who reported the desire for no additional children tended to favour the more reliable techniques. Surprisingly, the two measures of status failed to reveal significant relationships with the selection of a given technique.

In Australia, Belgium, Denmark, England and Wales, Holland, Italy, New Zealand, Norway, Scotland, Sweden and Switzerland there was a substantial decline in dizygotic twinning rates during the 1960s. In Portugal, Spain and Japan there was a lesser decline and in the US there was little change. In many of the countries for which evidence is available, it seems that these declines all started at about the same time in the late 1950s. It has been suggested that the recent decline in Scotland occurred mainly in middle class women; in contrast it is suggested here that the earlier decline in the US during the years 1933–58 was more characteristic of lower class women. For England and Wales and for Scotland, the recent decline (unlike that in the US 1933–58) occurred about equally in young and older women, so that the causes of the declines in the US in 1933–58 and in other countries at present may be different. In the absence of hard evidence, it is speculated that the current declines may be due to hormonal or pesticidal substances widely used in agriculture.

Monozygotic twinning rates have shown no similar trend so that pregnancy wastage does not seem to be implicated.

The distribution of the interval between (say) first and third confinements is the product of the distributions of the intervals between first and second and second and third confinements provided these two confinement intervals are independent. In this paper we use some specially provided NSW data to consider the question of the independence of the intervals between various confinements. It is shown that there is some indication of a positive association between confinement intervals, but that this association is not very great.

The common belief that childlessness is positively associated with instability of marriage derives from official statistics which appear to show higher divorce rates for childless than for fertile couples. The official findings are a procedural artifact, however, and the relationship shown is certainly exaggerated and possibly spurious.

The appropriate strategy in determining whether divorcees are relatively infertile is to find a population with disrupted marriages and measure its fertility experience. In doing so it is necessary to take note of the definition of fertility, the remarriage factor, and (most importantly) the duration of marriage. The official statistics use the conception of legal duration of marriage. Since this ignores separation before divorce, its use exaggerates the infertility of divorcees, as does failure to exclude remarriages. De facto duration of marriage (wedding to separation) is a superior statement of opportunity to conceive, and calculations on this basis eliminate or even reverse the fertility differential between divorcing and stable couples. Local figures are used to illustrate this effect, and the finding is supported by evidence from a sample of marriages ending in legal proceedings lesser than divorce. It is concluded that the alleged relationship between childlessness and instability of marriage is probably either non-existent or the reverse of that normally assumed, and that in any case measurement of the net overall effect of childlessness does not provide a helpful datum. An alternative strategy of research is suggested, which would seek patterns of effect rather than net overall effect, taking heed of relevant variables, and also considering all forms of marital breakdown including marriages in which cohabitation continues only with disharmony.

Birth weight correlation in full sibs is estimated from data for 4229 sibships. It is shown that, when it is necessary to adjust individual observations before the calculation of familial correlations, the genetic implications of the method of choice should be examined. It is shown that full sib correlation increases from 0·47 to 0·52 for unadjusted birth weights when the weight of the first born is excluded. After adjustments for sex, parity, gestation and changes in maternal weight a correlation of 0·56 is obtained.