A longitudinal study of twenty-six breast-feeding and twelve non-breast-feeding postpartum women was conducted in Assiut, Egypt in order to determine the time that ovulation resumed after childbirth, and the effect of breast-feeding frequency on the period of lactational anovulation. Breastfeeding women experienced the onset of follicular development, vaginal bleeding, ovulation and pregnancy significantly later than women who did not breast-feed. Ovulatory and non-ovulatory breast-feeders reported similar frequencies of breast-feeding episodes. The introduction of dietary supplements commonly preceded ovulation. An algorithm using three simple variables observable to the breast-feeding mother was found to predict up to 100% of the first ovulations. All breast-feeding women who did not give supplements and did not have a vaginal bleeding episode by 6 months postpartum were anovular by strict criteria for ovulation. Ovulation did not precede bleeding or supplementation in the women who experienced these events before 6 months, yielding a highly effective formula for preventing unplanned pregnancy by the informed use of breast-feeding.

Ten narrative studies involving family histories of 262 children of gay fathers and lesbian mothers were evaluated statistically in response to Morrison's (2007) concerns about Cameron's (2006) research that had involved three narrative studies. Despite numerous attempts to bias the results in favour of the null hypothesis and allowing for up to 20 (of 63, 32%) coding errors, Cameron's (2006) hypothesis that gay and lesbian parents would be more likely to have gay, lesbian, bisexual or unsure (of sexual orientation) sons and daughters was confirmed. Percentages of children of gay and lesbian parents who adopted non-heterosexual identities ranged between 16% and 57%, with odds ratios of 1.7 to 12.1, depending on the mix of child and parent genders. Daughters of lesbian mothers were most likely (33% to 57%; odds ratios from 4.5 to 12.1) to report non-heterosexual identities. Data from ethnographic sources and from previous studies on gay and lesbian parenting were re-examined and found to support the hypothesis that social and parental influences may influence the expression of non-heterosexual identities and/or behaviour. Thus, evidence is presented from three different sources, contrary to most previous scientific opinion, even most previous scientific consensus, that suggests intergenerational transfer of sexual orientation can occur at statistically significant and substantial rates, especially for female parents or female children. In some analyses for sons, intergenerational transfer was not significant. Further research is needed with respect to pathways by which intergenerational transfer of sexual orientation may occur. The results confirm an evolving tendency among scholars to cite the possibility of some degree of intergenerational crossover of sexual orientation.

Eight hundred and eighty-seven students from two major universities in Delhi, India, were surveyed, using a self-administered questionnaire, about their sexual knowledge, attitudes and behaviour. The data show that female students seem to be rejecting traditional Indian repressive sexual standards of premarital and non-procreative sex and the gender differences are beginning to narrow. Despite their sexual awareness, the students were highly ignorant of the facts of life. Being male and married did not make them more knowledgeable.

Data were analysed from the 1973 surveys of the Nigerian segment of the Changing African Family (CAFN) Project which covered Yoruba women and men in Ibadan and the western state of Nigeria. The Yoruba women in monogamous unions and those in polygynous unions show slightly varying levels of fertility, measured as mean number of children ever born. Most of this variation can be attributed to other variables; type of union of the women does not significantly affect their fertility level.

Urinary oestrogen and pregnanediol values were measured in 24 boys and 38 girls between the ages of 2 and 13 years. Longitudinal studies were conducted on eight girls, two of whom collected for periods of 4 and 5 years which included menarche and in one case establishment of ovulation. Highly sensitive assay methods were developed for measuring the very small amounts of oestrone, oestradiol and oestriol and pregnanediol present in the urine of young children. The total oestrogen values were within the submicrogram range of 0·1–0·5 μg/24 hr in the children aged 2–8 years, with no differences seen between the boys and girls. After the age of 8 years, oestrogen values above 1 μg/24 hr began to be encountered and by age 11½ years the majority of subjects were recording oestrogen values above this figure. The rise in the oestrogen values was more rapid in the girls than in the boys. Evidence was presented that a value of approximately 1 μg/24 hr represents the minimum oestrogen production for the initiation of breast development. The oestrogen values were fluctuating with irregular periodicities at all ages and the gradual general rises seen after the age of 8 years could be arrested at any stage for a year or more. Menarche was preceded by marked periodic fluctuations in oestrogen output which peaked above 15 μg/24 hr. In all subjects studied, the initial bleeding cycles were anovulatory as judged by the low pregnanediol values, the usual pattern being one of fluctuating oestrogen production. One subject was studied fully through to the establishment of ovulation, which first occurred 12 months after menarche. The approach of ovulation was indicated by pre-menstrual rises in pregnanediol which increased in amplitude from 0·4 mg/24 hr until finally 2 mg/24 hr was exceeded (the value accepted for ovulation). Evidence was presented that the interval from menarche to ovulation in different individuals was very variable, extending from ovulation at menarche itself to periods of more than a year. Recording of self-observed symptoms of production of cervical mucus could be of considerable value in documenting these events in larger populations.

Two samples of births were used to examine the effect of son preference and population policy on sex ratios in Hebei and Shaanxi provinces of China. The results from all births to women aged 15–49 in the 1985 In-Depth Fertility Survey indicated a strong son preference but no clear policy impact on sex ratios at different birth orders. In a sample of selected births during 1975–84 to women aged 40 or under, the mixed influences of son preference and population policy were clearly reflected in the high and rising overall ratios at birth, and the increasing sex ratios with parity. Possible explanations for these findings are discussed.

Consanguinity is studied in a large sample of marriages among Dhangars of Maharashtra, India. The 22 endogamous castes included in the study show great variation in incidence, about an overall frequency of 26.4%. Matrilateral first cross-cousin unions are more frequency than patrilateral, and maternal uncle-niece nuions least frequent. Geograbhical differences are conspicuous, and all three types of consanguineous union show characteristic patterns; matrilateral unions increase in frequncy northwards, patrilateral and uncle-niece decrease northwards. The inbreeding levels among the Dhangars are high compared to other Maharashtrian groups, but substantially lower than in southern Dravidian speaking groups.

This study investigated gender difference in the effects of social support, including emotional support and instrumental support (such as help when sick and financial assistance), and social activities on perceived health of middle-aged and older adults in South Korea. Data were acquired from 3771 men and 4954 women aged 40 years and older who participated in the 2005 cross-sectional survey of the Seoul Citizens Health and Social Indicators Survey. Using multiple regression analysis, both age- and gender-specific differences related to social support and engagement in social activities and self-rated poor health were examined. Poor emotional support from close friends, relatives or someone with whom one could talk about worries was strongly associated with poor self-rated health in men, with the greatest effect in older men. Lack of engagement in social activities was associated with self-rated poor health in older adults, especially in older men. Poor instrumental support was associated with perceived poor health only in middle-aged women. As a health improvement strategy for men aged 65 years and older especially, emotional support should be considered. Measures should be considered for encouraging social activities by older adults, particularly older men.

This study was carried out to quantify secular trends in seasonal variation in births in Malta, a small Mediterranean country where the vast proportion of births occur in wedlock due to a predominantly Roman Catholic population. It also related such variations to seasonal variation in marriages. Annual seasonal peaks of marriages and births were analysed over the period 1950–1996 by X11 ARIMA. A significant peak in marriages (n=111,932) in the third quarter of the year was found for almost the entire period under study. This was paralleled by a peak in births (n=299,558) for the period 1970–1996, which lagged after the peak in marriages by 13–14 months. For the period 1994–1996, when monthly data for monthly pregnancies were available by pregnancy order, the peak in births was caused by first pregnancies only. Seasonal patterns in births occur almost universally due to cultural and/or biometeorological factors. The best known patterns include those of the southern United States, where births decline in April and May, and in northern Europe, where births peak in March and April. In Malta, the late summer peak in births appears to be due to a practical and planned approach by Maltese couples to contraceptive planning, probably influenced by the Roman Catholic ethos and social pressures, with unprotected intercourse occurring only after marriage. In Malta, birth control, albeit by so-called natural methods, was introduced in the 1960s. Prior to this period, births peaked towards the beginning/end of the year, and this may be the more natural seasonality of births in Malta.

In this study it is hypothesized that taller individuals are more likely to move up the scale of educational attainment compared with shorter individuals from the same social background. Three national cohorts of 19-year-old males were considered: 29,464 born in 1967 and surveyed in 1986, 31,062 born in 1976 and surveyed in 1995, and 30,851 born in 1982 and surveyed in 2001. Four social variables were used to describe the social background of each conscript in the three surveys: degree of urbanization, family size, and parental and maternal educational status. The educational status of each conscript was classified into two groups: (1) those who were secondary school students or graduates, or who had entered college, and (2) those who had completed their education at the primary school level or who had gone to a basic trade school. Multiple binomial logistic regressions were used to estimate the relative risk of achieving higher educational status by 19-year-old males relative to height and the four social factors. Consistently across the three cohorts the odd ratios (ORs) indicate that height exerts an independent and significant effect on the attained level of education at the age of 19 years in males (1986: OR=1·24, p<0·001; 1995: OR=1·24, p<0·001; 2001: OR=1·20, p<0·001). Two possible, not mutually exclusive, selective mechanisms are postulated and discussed: ‘passive’ and ‘active’ action.

I read with great interest Akrami and Osati’s article entitled ‘Is consanguineous marriage religiously encouraged? Islamic and Iranian considerations’ published in the March 2007 issue of the Journal of Biosocial Science (Akrami & Osati, 2007). The authors showed that in many Islamic sources, there is no sign that could be described as encouraging cousin marriages. I would like to make a few comments about it.

Several studies report that women exposed to intimate partner violence (IPV) are less likely to use contraception, but the evidence that violence consistently constrains contraceptive use is inconclusive. One plausible explanation for this ambiguity is that the effects of violence on contraceptive use depend on whether couples are likely to have conflicting attitudes to it. In particular, although some men may engage in violence to prevent their partners from using contraception, they are only likely to do so if they have reason to oppose its use. Using a longitudinal follow-up to the Indian National Family Health Survey (NFHS-2), conducted among a sample of rural, married women of childbearing age, this study investigated whether the relationship between IPV and contraceptive use is contingent on whether women’s contraceptive intentions contradict men’s fertility preferences. Results indicate that women experiencing IPV are less likely to undergo sterilization, but only if they intended to use contraception and their partners wanted more children (Average Marginal Effect (AME)=−0.06; CI=−0.10, −0.01). Violence had no effect on sterilization among women who did not plan to use contraception (AME=−0.02; CI=−0.06, 0.03) or whose spouses did not want more children (AME=−0.01; CI=−0.9, 0.06). These results imply that violence enables some men to resolve disagreements over the use of contraception by imposing their fertility preferences on their partners. They also indicate that unmet need for contraception could be an intended consequence of violence.

In Morocco, the beginning of the nutritional transition is closely linked to social and economic transformations and changes in behaviour and traditional lifestyles. The objective of this study is to describe the current pattern of food consumption and the nutritional status of adolescents in the province of Ouarzazate and its association with parents' educational level. The sample comprises 327 high school students from Ouarzazate: 135 (41.3%) boys and 192 (58.7%) girls (age range 15–20 years). For both boys and girls, the results show lower height and BMI z-scores than the WHO reference values. Adolescents whose parents have a low educational level have lower height/age and BMI/age z-scores than those whose fathers have a high educational level. No differences are observed in total daily energy intake depending on fathers' educational level, but the energy provided by lipids is higher in adolescents whose fathers have a high educational background. The quality of fats consumed (MUFA+PUFA/SFA) is better among those boys whose fathers have low education, but no differences are observed for girls. The process of nutritional transition is not uniform in the sample, but depends on the socioeconomic characteristics of population groups, which include, among others, accessibility of certain food, differences in habits and lifestyles related to energy expenditure, and higher prevalence of overweight and obesity in more favoured groups.

China's one-child policy has been quite successful in bringing down the country's fertility level but has produced a large number of one-child families. The risk of one-child families losing their only child has not received enough attention. In this paper, using an extension of Goldman & Lord (1983)'s method to measure widowhood, period life-table data from China's 2000 population census are used to examine age-specific and cumulative probabilities of mothers losing their only child. It is found that a mother faces a 14.94% probability of losing a son, and 12.21% probability of losing a daughter. As the age of first-time mothers increases, the probability of losing a child declines. Urban and rural mothers have different indices regarding the loss of children. Based on these findings the prospects for China's one-child policy are discussed.

Different methods of obtaining information in medical and social research present problems of interpretation for the researcher. However, there are few systematic studies on the extent of the lack of concordance yielded by different methods. This paper uses data from a randomized controlled trial of social support in pregnancy to examine this issue in relation to three methods of data collection—medical records, home interviews and a postal questionnaire—on the following topics: obstetric history; smoking, alcohol use, number of antenatal hospital visits, bleeding and depression in pregnancy; length of labour; baby's sex, birthweight and neonatal health problems; and ethnicity. Considerable discrepancies are found comparing the different data sources. These suggest that mothers may be more reliable sources of information than medical records, and that the anonymity of a postal questionnaire may provide higher estimates than home interviews on some sensitive topics, such as smoking in pregnancy.

Medical records from maternity clinics in three Norwegian cities, Oslo, Bergen and Trondheim, have been used to study the relationship between lactation and post-partum amenorrhoea during the period 1860–1964. Resumption of menses after a period of post-partum amenorrhoea has been examined separately during lactation, after cessation of lactation, and in the absence of lactation, in 5250 cases. During ongoing lactation the median duration of post-partum amenorrhoea was found by survival analysis to be 12 months for women who had given birth before 1900 and 6 months for women who had given birth after 1900. In a Cox regression analysis, age of menarche and parity were found to influence the duration of post-partum amenorrhoea, in addition to the child's birth year. With a later age of menarche there was longer amenorrhoea, and primiparae resumed menses earlier than multiparae. After cessation of breast-feeding the median duration of amenorrhoea was 1 month, the only variable significantly influencing it being the age of menarche, a younger age showing a shorter duration. In the absence of lactation the survivor function started to decline after 3–4 weeks, and had a half-life of 2 months.

None of the variables indicating the woman's social condition seemed to influence the duration of amenorrhoea. The decline in the duration of post-partum amenorrhoea during ongoing lactation from 1860 until today is therefore probably caused by a changed breast-feeding pattern rather than by improved nutrition for women giving birth.

Differentials in child survival in Bangladesh have been examined using a number of socioeconomic and environmental factors on data from the 1989 Bangladesh Fertility Survey. Multivariate analysis reveals that both wife's and husband's education and household electricity show a significant positive association with child survival. The respondent's working status exerts a significant negative influence. Wife's education has a greater influence on child survival in Bangladesh than that of husband's education.

Adolescents are the focus of many interventions that aim to prevent HIV transmission. In order for these interventions to be effective, it is essential to understand adolescents' sexual behaviour. Using data collected in Yaoundé, Cameroon, in 1997, the study analysed risk exposure and HIV prevalence among 426 men and 510 women aged 15–24. Although risky behaviours seem to be more prevalent among young men, their HIV prevalence remains under 1%. In contrast, HIV prevalence is high among young women (7·5%), even those who report having had few sexual partners. Mixing patterns among sexual partners, and especially the age difference between men and women, do not seem to be sufficient to explain the large male–female discrepancy in HIV prevalence that is evident in these data. The results are therefore probably due to a greater susceptibility to infection of young women than men. This study highlights the necessity of reinforcing prevention campaigns among youth and fighting the obstacles that continue to impede the use of condoms in this population.

This study estimates the effect of dysgenic trends in Taiwan by exploring the relationships among intelligence, education and fertility. Based on a representative adult sample, education and intelligence were negatively correlated with the number of children born. These correlations were stronger for females. The decline of genotypic intelligence was estimated as 0.82 to 1.33 IQ points per generation for the Taiwanese population.

A geographically stratified cross-sectional survey was conducted in 2002 to investigate household-level factors associated with use of mosquito control measures and self-reported malaria in Malindi, Kenya. A total of 629 households were surveyed. Logistic regressions were used to analyse the data. Half of all households (51%) reported all occupants using an insecticide-treated bed net and at least one additional mosquito control measure such as insecticides or removal of standing water. Forty-nine per cent reported a history of malaria in the household. Of the thirteen household factors analysed, low (OR=0·23, CI 0·11, 0·48) and medium (OR=0·50, CI 0·29, 0·86) education, mud–wood–coral (OR=0·0·39, CI 0·24, 0·66) and mud block–plaster (OR=0·47, CI 0·25, 0·87) wall types, farming (OR=1·38, CI 1·01, 1·90) and travel to rural areas (OR=0·48, CI 0·26, 0·91) were significantly associated with the use of mosquito control, while controlling for other covariates in the model. History of reported malaria was not associated with the use of mosquito control (OR=1·22, CI 0·79, 1·88). Of the thirteen covariates analysed in the second model, only two household factors were associated with history of malaria: being located in the well-drained stratum (OR=0·49, CI 0·26, 0·96) and being bitten while in the house (OR=1·22, CI 0·19, 0·49). These results suggest that high socioeconomic status is associated with increased household-level mosquito control use, although household-level control may not be enough, as many people are exposed to biting mosquitoes while away from the house and in areas that are more likely to harbour mosquitoes.