Showing papers on "Fertility published in 1998"
TL;DR: The completed fertility rate (CFR) as discussed by the authors measures the average number of births 50-year-old women had during their past reproductive years, but it has the disadvantage of representing past experience: women currently aged 50 did most of their childbearing two to three decades ago when they were in their 20s and 30s.
Abstract: ESTIMATES OF FERTILITY are among the most widely used demographic statistics. In many developing countries recent levels and trends in fertility are avidly watched by policymakers, family planning program managers, and demographers to determine whether and how rapidly fertility is moving in the desired downward direction. In much of the developed world, where fertility is now at historic lows, these same statistics are examined for signs of an upturn in fertility back to the replacement level needed to prevent future declines in population size. Given this interest in measuring human reproduction, it is desirable for users of fertility statistics to understand the strengths and weaknesses of available indicators. It is particularly important to avoid basing policies on statistics that give potentially misleading information. Although the demographic literature offers many measures of fertility, the total fertility rate (TFR) is now used more often than any other indicator. The TFR is defined as the average number of births a woman would have if she were to live through her reproductive years (ages 1549) and bear children at each age at the rates observed in a particular year or period. It is a hypothetical measure because no real group of women has experienced or will necessarily experience these particular rates. The actual childbearing of cohorts of women is given by the completed fertility rate (CFR), which measures the average number of births 50-year-old women had during their past reproductive years. The CFR measures the true reproductive experience of a group of women, but it has the disadvantage of representing past experience: women currently aged 50 did most of their childbearing two to three decades ago when they were in their 20s and 30s. The advantage of the TFR is that it measures current fertility and therefore gives up-to-date information on levels and trends in fertility. Another reason for the popularity of the TFR is its ease of interpretation compared with some other measures. Most interested persons will have little
754 citations
TL;DR: Weight loss should be considered as a first option for women who are infertile and overweight, and the cost savings of the programme were considerable.
Abstract: Obesity affects ovulation, response to fertility treatment, pregnancy rates and outcome. In this prospective study, a weight loss programme was assessed to determine whether it could help obese infertile women, irrespective of their infertility diagnosis, to achieve a viable pregnancy, ideally without further medical intervention. The subjects underwent a weekly programme aimed at lifestyle changes in relation to exercise and diet for 6 months; those that did not complete the 6 months were treated as a comparison group. Women in the study lost an average of 10.2 kg/m2, with 60 of the 67 anovulatory subjects resuming spontaneous ovulation, 52 achieving a pregnancy (18 spontaneously) and 45 a live birth. The miscarriage rate was 18%, compared to 75% for the same women prior to the programme. Psychometric measurements also improved. None of these changes occurred in the comparison group. The cost savings of the programme were considerable. Prior to the programme, the 67 women had had treatment costing a total of A$550,000 for two live births, a cost of A$275,000 per baby. After the programme, the same women had treatment costing a total of A$210,000 for 45 babies, a cost of A$4600 per baby. Thus weight loss should be considered as a first option for women who are infertile and overweight.
729 citations
TL;DR: The study suggests that the current WHO guidelines for normal semen quality should be used with caution, as some men with sperm counts above the lower limit of the normal range defined by WHO may in fact be subfertile.
703 citations
TL;DR: The evidence presented in this review is compelling because of the consistency of effect across different study designs, sample size and types of outcome, however, continued reassurance is needed that the calculated overall effect is not in fact due to confounding variables.
Abstract: The high prevalence of smoking among women in their reproductive years continues to be a matter of concern. The negative effects of smoking on general health are well known, but smoking may also affect fertility. The objective of the present study was to perform a systematic review of the literature to determine whether there is an association between smoking and risk of infertility in women of reproductive age, and to assess the size of this effect. In the 12 studies used for this meta-analysis, the overall value of the odds ratio (OR) for risk of infertility in women smokers versus non-smokers was 1.60 [95% confidence interval (CI) 1.34-1.91]. Studies of subfertile women undergoing in-vitro fertilization (IVF) treatment also show a reduction in fecundity among women smokers. A meta-analysis of nine studies found an OR of 0.66 (95% CI 0.49-0.88) for pregnancies per number of IVF-treated cycles in smokers versus non-smokers. Despite the potential limitations of meta-analyses of observational studies, the evidence presented in this review is compelling because of the consistency of effect across different study designs, sample size and types of outcome. However, continued reassurance is needed that the calculated overall effect is not in fact due to confounding variables.
456 citations
TL;DR: It is found that the incidence of epilepsy was higher in elderly people and lower in children, and women aged 25-39 years with treated epilepsy have significantly lower fertility rates than those in the general population.
378 citations
TL;DR: Analysis of reproductive preferences and behavior of married men and their wives in 18 developing countries indicates that spousal age differences ranged from 2.7 years in Brazil to 12.2 years in Senegal, and husbands desired family size was higher in western compared to eastern Africa and was higher than womens DFS.
Abstract: This study examined the reproductive preferences and behavior of married men and their wives in 18 developing countries. Data were obtained from the Demographic and Health Surveys during 1990-96 in 13 sub-Saharan African 2 North African 2 Asian and a Latin American country. Only 2 countries did not have male data. The sample included polygamous couples but the effects of fertility intentions (FI) on couples contraceptive behavior refers only to monogamous couples with a nonpregnant wife. Findings indicate that spousal age differences ranged from 2.7 years in Brazil to 12.2 years in Senegal. Literacy of males varied from 10% in Senegal to 77% in Zimbabwe. The proportion of husbands desiring at least 2 children more than did the wife ranged from 27% in Niger to 70% in Bangladesh. Fewer than 50% of couples agreed in 8 of the 13 sub-Saharan African countries. The mean number of children desired by husbands ranged from 2.9 in Brazil to 11.5 in Niger. In 11 sub-Saharan countries the desired number of children exceeded 5. Husbands desired family size (DFS) was higher in western compared to eastern Africa and was higher than womens DFS. Gender differences in DFS were negligible outside Africa. 10-26% of partners disagreed on the desire for more children. 21-40% disagreed on when to have more children. Husbands reported higher modern method use. Joint FI significantly determined modern method use in 15 countries. After controlling for effects of spouses characteristics joint FI was a significant predictor in 9 countries. Contraceptive use was more likely when couples desired a stop to childbearing.
373 citations
01 Jan 1998
TL;DR: In the post-transitional period, fertility has dropped below the replacement level in virtually every population that has moved through the demographic transition as mentioned in this paper. But fertility has not yet stabilized at or near the level of replacement.
Abstract: THE TIMING OF the onset of contemporary fertility transitions and the pace of change during their early phases have been central concerns of researchers and policymakers in recent decades. Demographers and social scientists have studied survey data with detailed information about reproductive behaviors and attitudes of individuals in many countries. This research has provided new insights into the determinants of reproductive behavior and has contributed to the development of increasingly refined and realistic theories of fertility change. Policymakers and program managers in the developing world have been concerned about the contribution of high fertility to rapid population growth and poor reproductive health, and they have focused on implementing effective programs-in practice, mostly family planning programs-to reduce high and unwanted fertility. Until recently, less attention had been given to determinants and consequences of fertility in post-transitional societies. Conventional demographic theories have little to say about the level at which fertility will stabilize at the end of the transition. However, it is usually assumed that population growth in the long run will be near zero, which implies that fertility will on average be close to the replacement level of about 2.1 births per woman (Demeny 1997; Caldwell 1982; Freedman and Berelson 1974). This assumption is, for example, incorporated in past population projections of the United Nations and the World Bank (medium variants). If fertility in contemporary post-transitional societies had indeed leveled off at or near the replacement level, there would have been limited interest in the subject because this would have been expected. However, fertility has dropped below the replacement level-sometimes by a substantial margin-in virtually every population that has moved through the demographic transition. If future fertility remains at these low levels, populations will decline in size and will age rapidly. These demographic developments in
350 citations
TL;DR: A systematic test of two alternatives of the human menopause using field data from two species in which grandmothers frequently engage in kin-directed behaviour finds that elderly females do not suffer increased mortality costs of reproduction, nor do post-reproductive females enhance the fitness of grandchildren or older children.
Abstract: In female mammals, fertility declines abruptly at an advanced age. The human menopause is one example, but reproductive cessation has also been documented in non-human primates, rodents, whales, dogs, rabbits, elephants and domestic livestock. The human menopause has been considered an evolutionary adaptation, assuming that elderly women avoid the increasing complications of continued childbirth to better nurture their current children and grandchildren. But an abrupt reproductive decline might be only a non-adaptive by-product of life-history patterns. Because so many individuals die from starvation, disease and predation, detrimental genetic traits can persist (or even be favoured) as long as their deleterious effects are delayed until an advanced age is reached, and, for a given pattern of mortality, there should be an age by which selection would be too weak to prevent the onset of reproductive senescence. We provide a systematic test of these alternatives using field data from two species in which grandmothers frequently engage in kin-directed behaviour. Both species show abrupt age-specific changes in reproductive performance that are characteristic of menopause. But elderly females do not suffer increased mortality costs of reproduction, nor do post-reproductive females enhance the fitness of grandchildren or older children. Instead, reproductive cessation appears to result from senescence.
335 citations
01 Jan 1998
TL;DR: The recent literature on the effects of welfare on marriage and fertility includes studies employing a wide variety of methodologies and data sets and covering different time periods as discussed by the authors, and the current consensus is that the welfare system probably has some effect on these demographic outcomes.
Abstract: The recent literature on the effects of welfare on marriage and fertility includes studies employing a wide variety of methodologies and data sets and covering different time periods. A majority of the studies show that welfare has a significantly negative effect on marriage or positive effect on fertility rather than none at all, and thus the current consensus is that the welfare system probably has some effect on these demographic outcomes. Considerable uncertainty surrounds this consensus because a sizable minority of the studies find no effect at all, because the magnitudes of the estimated effects vary widely, and because puzzling and unexplained differences exist across the studies by race and methodological approach. At present, and with the information provided in the studies, the source of these disparities cannot be determined. While a neutral weighing of the evidence still leads to the conclusion that the welfare system affects marriage and fertility, research needs to be conducted to resolve the conflicting findings. The Effect of Welfare on Marriage and Fertility: What Do We Know and What Do We Need to Know? The research literature over the last 30 years on the effects of welfare on marriage and fertility includes studies employing a variety of methodologies and data sets and covering different time periods. Several studies were conducted in the 1970s and early 1980s, but a second wave of studies began in the mid-1980s and is still under way. Based on the early work, a consensus among researchers developed a decade or so ago that the welfare system had no effect on marriage and fertility. However, a majority of the newer studies show that welfare has a significantly negative effect on marriage or positive effect on fertility rather than none at all. Because of this shift in findings, the current consensus is that the welfare system probably has some effect on these demographic outcomes. However, considerable uncertainty surrounds this consensus because a significant minority of the studies find no effect at all, because the magnitudes of the estimated effects vary widely, and because puzzling and unexplained differences exist across the studies by race and methodological approach. For example, the findings show considerably stronger effects for white women than for black or nonwhite women, despite the greater participation rates of the latter group in the welfare system. Also, the findings often differ when demographic outcomes are correlated with welfare generosity in different ways—variation in welfare benefits across states in a particular year, for example, versus variation in welfare benefits over time. Whether the differences in study findings result from inherent differences in different data sets or from differences in the way the data are analyzed—for example, in estimating techniques, definitions of variables, characteristics of the individuals examined, and other influences controlled for—is difficult to determine because most authors do not systematically attempt to determine why their findings differ from those of other studies. This paper summarizes the relevant literature and discusses the differences across studies. Because of the diversity of findings, methodological considerations necessarily must be a major focus of the discussion. Section I provides background on the U.S. welfare system and those aspects of its 2 structure relevant to marriage and fertility and discusses the context of social science theories of marriage and fertility in which the welfare system plays a role. Section II outlines the different questions of interest and discusses those questions that have been addressed in the research literature. Section III discusses the methodological approach taken in the research literature toward the question and contrasts the method of experimentation with the nonexperimental method of using natural program variation. Broad trends in the U.S. on demographic outcomes and the welfare system are presented in Section IV; these trends establish a set of basic patterns in the data. Section V reviews the multivariate research studies on the question, compares and contrasts their approaches, and discusses possible reasons for the diversity of findings. Finally, suggestions for future research are outlined in Section VI.
267 citations
TL;DR: There is a generational effect, characterized by more variability of age at first birth and delay to first birth in the younger than in the older generations, and this tendency was more accentuated in some populations.
Abstract: The occurrences and timing of reproduction-related events, such as menarche, first birth, and menopause, play major roles in a woman's life. There is a lack of comparative information on the overall patterns of the ages at and the timing between these events among different populations of the world. This study describes the variability in reproductive factors across populations in Europe, the Americas, Asia, Australia, and Africa. The study sample consisted of 18,997 women from 13 centers in 11 countries interviewed between 1979 and 1988 who comprised the control group in a World Health Organization international, multicenter case-control study of female cancers. All were surveyed with the same questionnaire and methodology. Overall, a typical woman in this study reached menarche at age 14 years and delivered her first live child 8 years later, at age 22. She was 50 years old at natural menopause and had had 36 years of reproductive life. The median ages at menarche varied across centers from 13 to 16 years. For all centers, the median age at first livebirth was 20 or more years, with the largest observed median (25 years) occurring in China. The median delay from menarche to first livebirth ranged from 5 to 11 years. Among the centers, the median age at natural menopause ranged between 49 and 52 years. In most populations, younger women had a first birth at a later age than did older women. This tendency was more accentuated in some populations. These results reveal, perhaps for the first time, the variability of reproductive histories across different populations in a large variety of geographic and cultural settings. Except for menopause, international variability is substantial for both biologically related variables (age at menarche) and culturally related variables (age at first birth). There is a generational effect, characterized by more variability of age at first birth and delay to first birth in the younger than in the older generations.
256 citations
TL;DR: Results indicate that fertility is improved through exercise and sensible eating patterns when conducted in a group environment, and the mechanisms for this are unclear but may be associated with changes in sensitivity to insulin.
Abstract: Obesity has significant consequences for the reproductive system, depending upon the amount and distribution of body fat. Epidemiological evidence clearly shows that being overweight contributes to menstrual disorders, infertility, miscarriage, poor pregnancy outcome, impaired fetal well-being and diabetes mellitus. Central adiposity is particularly important in clinical sequelae associated with an increased body mass index. The advent of assisted reproduction highlights the problems of being overweight, and the use of gonadotrophins in ovulation induction and in vitro fertilization is more difficult when the subject is overweight. Weight loss has marked effects on improving the menstrual cycle and promoting spontaneous ovulation and fertility. Results indicate that fertility is improved through exercise and sensible eating patterns when conducted in a group environment. The mechanisms for this are unclear but may be associated with changes in sensitivity to insulin.
TL;DR: Higher education is associated with lower rates of adolescent childbearing, but other socioeconomic changes cancel or reduce this effect in several countries, and declines are less prevalent and some small increases have occurred in Latin America.
Abstract: This article discusses the current levels and recent trends in the rate of adolescent childbearing, the timing of the first birth, and births to unmarried women for 43 developing countries. Differences in rates of adolescent childbearing by residence and level of education are also examined. The analysis is based on nationally representative fertility surveys. Substantial declines in adolescent fertility have occurred in North Africa and Asia, but levels are still high in some countries. Declines are beginning to occur in sub-Saharan Africa, but current levels are still high in most countries of this region, and the proportion of births to unmarried adolescents is increasing in some countries. In Latin America, where the level of teenage childbearing is moderate, declines are less prevalent and some small increases have occurred. Higher education is associated with lower rates of adolescent childbearing, but other socioeconomic changes cancel or reduce this effect in several countries.
Journal Article•
TL;DR: In populations that do not use contraceptives, HIV-positive women have lower fertility principally as a result of foetal losses consequent to infection with HIV and coinfection with other sexually transmitted diseases; behavioural factors tend to enhance this differential.
Abstract: Growing evidence indicates that HIV-1 infection is having a measurable impact upon fertility in the countries of sub-Saharan Africa which have been seriously affected by the epidemic. The impact is due to the direct biological effects of HIV on the fecundity of infected women as well as to its indirect effects upon behavior in the general population. Data from case-control studies and theoretical predictions from a model of the proximate determinants of fertility and HIV incidence were used to assess the impact of HIV upon fertility in Africa. Analysis of the data shows that the fertility of HIV-positive women is lower than that of HIV-negative women in all but the youngest age group with the differential increasing with womens age and epidemic duration. Selection for the early start of sexual activity explains the reverse pattern at younger ages. Lower fertility among HIV-positive women causes a population attributable decline in total fertility of 0.4% for each percentage point HIV prevalence in the general female population.
TL;DR: The striking regularity in fertility reduction across all ages indicates that contraception is practiced mostly for birth spacing and that contraceptive methods have gained wide acceptance among younger cohorts.
Abstract: This study presents an assessment of fertility trends in 23 countries of sub-Saharan Africa. It examines trends and differentials in proximate determinants and fertility preferences. Findings from the Demographic and Health Surveys for these countries over a period of 15 years show that desired family size has decreased significantly. Two-thirds of the countries examined show evidence of fertility decline, a particularly rapid decline in the cases of Kenya and Zimbabwe. Areas with higher education for women and lower child mortality experienced larger reductions in fertility and desired family size. Contraceptive use far exceeds other proximate determinants in explaining these changes. The striking regularity in fertility reduction across all ages indicates that contraception is practiced mostly for birth spacing and that contraceptive methods have gained wide acceptance among younger cohorts. Good prospects are seen for further intensification of fertility declines in East Africa and urban West Africa. However, low levels of education and high child mortality make rapid changes unlikely in rural West Africa.
TL;DR: The literature on health consequences of adolescent sexual behavior and child-bearing in sub-Saharan Africa is reviewed, and it is suggested that, in addressing the most serious health sequelae, sexual intercourse that occurs in early marriage and premaritally must both be considered.
Abstract: This article reviews the literature on health consequences of adolescent sexual behavior and child-bearing in sub-Saharan Africa, and the social and cultural context in which they occur. It suggests that, in addressing the most serious health sequelae, sexual intercourse that occurs in early marriage and premaritally must both be considered. Some limitations of the data are noted. Despite the excess risk to which adolescents are exposed, due both to custom and age-related vulnerability, differences between health effects among adult and adolescent women are often differences in degree. They are attributable to behavioral, social, and biological causes, exist in traditional and nontraditional settings, in union and out of union, and are exacerbated by declining ages at menarche, pressures of HIV/AIDS and STDs, and a dearth of appropriate services-especially for young people. Some current interventions are discussed, and the need for policy as well as medical intervention is stressed.
TL;DR: Cigarette smoking among teenagers was associated with increases in disomic sperm and a diminution in specific aspects of semen quality that may affect male fertility and may increase future chances of fathering offspring with aneuploidy syndromes.
TL;DR: Both sperm motility parameters and percent normal morphology are significant factors in predicting fertilization and pregnancy rates in IVF.
TL;DR: In this article, the inverse relationship between female participation and fertility appears to have broken down on a cross-country basis in the Western industrialized nations and Mediterranean Europe contributed to this breakdown with its combination of record low fertility and low participation.
Abstract: In this paper the authors address two related questions: first, why does the inverse relationship between female participation and fertility appear to have broken down on a cross-country basis in the Western industrialized nations and, second, why has Mediterranean Europe contributed to this breakdown with its combination of record low fertility and low participation? They re-examine the cross-country fertility--participation nexus from a long-term perspective and verify that there are no longer reasons to expect a systematic inverse relationship to hold for developed countries. The authors argue further that differences in participation and fertility reflect differences in the 'economics of the family' across countries. In Mediterranean countries, the combination of low fertility and low participation is favored by a family-centered welfare system, a family-biased production system and a family-oriented value system. And, contrary to widespread expectations, a very cohesive family has encouraged very low fertility. Copyright 1998 by Oxford University Press.
TL;DR: The recently completed panel survey in Morocco by the Demographic and Health Surveys was used to investigate the consistency of reporting of ideal number of children, reproductive intentions and the planning status of the last birth, finding the measure of reproductive intentions is the most consistent of the three.
Abstract: Information on reproductive attitudes is now routinely collected in fertility surveys in developing countries, and has become very important for understanding fertility behaviour. The quality of this information, however, is rarely assessed, partly due to lack of necessary data. In this paper, the recently completed panel survey in Morocco by the Demographic and Health Surveys (DHS) was used to investigate the consistency of reporting of ideal number of children, reproductive intentions and the planning status of the last birth. The validity of reproductive intentions for subsequent fertility behaviour was also examined. The findings indicate that the three measures of reproductive attitudes are subject to different degrees of measurement error. The measure of reproductive intentions is the most consistent of the three, followed by ideal number of children. The latter is much more consistent at the aggregate level than at the individual level. The reliability of the planning status of the last birth is marred, mainly by an unwanted child being reclassified as 'wanted' with time since the birth of the child. The reproductive intentions of women were also found to be positively related to their subsequent fertility.
TL;DR: This study compares notions of reproduction in Gambia and the West and analyzes 1992 baseline fertility survey data from the North Bank areas of rural Gambia, finding that fertility in the study sample was a 7.5 children/woman and women were eager to delay childbearing.
Abstract: This study compares notions of reproduction in Gambia and the West and analyzes 1992 baseline fertility survey data from the North Bank areas of rural Gambia. The sample includes 2980 women from 40 villages. The second phase was a multi-round survey in 1993 and 1994 in 8 of the original 40 villages among 270 women who had a pregnancy in the past 3 years. The Western model of fertility assumes a fixed life course and that contraception is a device for exploiting the time limits of fecundability. Gambian models of reproduction rely on a body resource framework that is based on declines in muscles strength and blood due to wearing life events. The Gambian fertility model includes more than fecundability in determining a womans ability to reproduce. Mishaps are destructive of reproductive capital. Mishaps include a heavy workload overly frequent childbearing a shortage of blood or simply being tired. Time and aging are not predictable forces that work independently of other life events. Reproduction is a potential to be realized without time limits. Fertility in the study sample was a 7.5 children/woman. Birth intervals were around 2.5 years. Contraceptive use was low and was mostly the pill and Depo-Provera. The rationale for contraception was the desire to protect the health of the children and the mother. Birth interval is regulated. Fertility behaviors change throughout the life cycle. Young women in their 30s spoke about being too old to bear another child. Older women were eager to delay childbearing. Contraceptive use was higher among women who had a miscarriage or stillbirth. A child spacing framework inadequately explained contraceptive behavior.
TL;DR: Results from the study suggest that effective behaviour change in Manicaland is facilitated by greater knowledge, experience and personal risk perception but obstructed by low female autonomy, marital status and economic status, and by male labour migration and alcohol consumption.
TL;DR: It is concluded that occupational heat exposure is a significant risk factor for male infertility, affecting sperm morphology and resulting in delayed conception.
Abstract: In humans, as in most mammals, spermatogenesis is temperature dependent. This temperature dependence has been clearly demonstrated by several experimental studies showing that artificial increases in scrotum or testicle temperature in fertile men reduce both sperm output and quality. Our knowledge of the effects of occupational heat exposure on male fertility comes mostly from a small number of epidemiological studies. We conducted an extensive review of these published reports, focusing on methodology and design (retrospective or prospective; reference group; number of subjects) and principal results (using several indicators such as the time taken to obtain a pregnancy or sperm characteristics). We concluded that occupational heat exposure is a significant risk factor for male infertility, affecting sperm morphology and resulting in delayed conception. The limits and biases involved in this type of research are also discussed.
TL;DR: The potential use of linear type scores as predictors of the health traits was investigated by regressing health traits on sire predicted transmitting abilities for type and the results indicate that some type traits may be useful as future selection criteria.
Abstract: The Dairy Information System (DAISY) was developed to record fertility and health information for use in research and to help farmers manage their farms. Data from 33 herds recording health and fertility over a 6-year period were used to study genetic relationships of several health, fertility and production traits. There were 10 569 records from 4642 cows of all parities. These were used to estimate genetic parameters for health: mastitis, lameness and somatic cell score (SCS), for fertility: calving interval, days to first service, conception to first service and for production: 305-day milk, butterfat and protein yields. Heritabilities for these traits were also estimated for the first three lactations. (Co)variances were estimated using linear, multitrait restricted maximum likelihood (REML) with an animal model. Mastitis and lameness were treated as all-or-none traits. The incidence of these diseases increased with lactation number, which may lead to variance component estimation problems, as the mean is linked to the variance in binomial distributions. Therefore, a method was used to fix the within-lactation variance to one in all lactations while maintaining the same mean. The heritability for SCS across lactations was 0·15. Heritabilities for other health and fertility traits were low and ranged between 0·013 and 0·047. All genetic correlations with the production traits were antagonistic implying that selection for yield may have led to a deterioration in health and fertility. The genetic correlation between SCS and mastitis was 0·65 indicating that indirect selection for improvements in mastitis may be achieved using somatic cell counts as a selection criterion. The potential use of linear type scores as predictors of the health traits was investigated by regressing health traits on sire predicted transmitting abilities for type. The results indicate that some type traits may be useful as future selection criteria.
TL;DR: It is recommended that a properly designed programme for semen cryopreservation for cancer patients should be developed in leading tertiary assisted conception centres, which have adequate facilities and experience for cryopReservation and can offer the whole range of appropriate assisted reproductive treatment and counselling.
Abstract: The improved survival in recent years of young malessuffering from cancer, and an understanding of thegonadotoxic effects ofchemotherapy treatment, have motiv-ated patients and clinicians to preserve fertility potentialbefore embarking on adjuvant therapy. Among 231 men(mean age 28.0; range 15–56 years) diagnosed with malig-nant disease and referred toour unit for semen cryopreserv-ation, 112 patients (49.8%) had reduced sperm quality of
TL;DR: An adaptive model of human reproductive decision-making, using a state-dependent dynamic model, is presented to show that, in the unpredictable environment of a traditional pastoralist society, high fertility and a biasing of wealth inheritance to a small number of children are frequently optimal.
Abstract: Life history theory concerns the scheduling of births and the level of parental investment in each offspring. In most human societies the inheritance of wealth is an important part of parental investment. Patterns of wealth inheritance and other reproductive decisions, such as family size, would be expected to influence each other. Here I present an adaptive model of human reproductive decision-making, using a state-dependent dynamic model. Two decisions made by parents are considered: when to have another baby, and thus the pattern of reproduction through life; and how to allocate resources between children at the end of the parents' life. Optimal decision rules are those that maximize the number of grandchildren. Decisions are assumed to depend on the state of the parent, which is described at any time by two variables: number of living sons, and wealth. The dynamics of the model are based on a traditional African pastoralist system, but it is general enough to approximate to any means of subsistence where an increase in the amount of wealth owned increases the capacity for future production of resources. The model is used to show that, in the unpredictable environment of a traditional pastoralist society, high fertility and a biasing of wealth inheritance to a small number of children are frequently optimal. Most such societies are now undergoing a transition to lower fertility, known as the demographic transition. The effects on fertility and wealth inheritance strategies of reducing mortality risks, reducing the unpredictability of the environment and increasing the costs of raising children are explored. Reducing mortality has little effect on completed family sizes of living children or on the wealth they inherit. Increasing the costs of raising children decreases optimal fertility and increases the inheritance left to each child at each level of wealth, and has the potential to reduce fertility to very low levels. The results offer an explanation for why wealthy families are frequently also those with the smallest number of children in heterogeneous, post-transition societies.
TL;DR: The authors summarized the recent evidence on levels, trends and differentials in achieved fertility, nuptiality, and contraceptive use in sub-Saharan Africa, and found that fertility decline in Africa is quite at odds with the popular perception of stationary or very limited fertility decline.
Abstract: The two most effective ways of converting parish register data into estimates of fertility, mortality, and nuptiality in the past are generalised inverse projection and family reconstitution. In general, they produce reassuringly similar results for England in the early modern period. An earlier version of inverse projection, using aggregative tabulations from 404 parishes, was employed to generate the demographic estimates presented in the Population history of England , while, 16 years later, data from 26 parish reconstitutions formed the basis for the findings published in English population history from family reconstitution . The more refined measures produced by family reconstitution have enabled some of the input parameters used in inverse projection to be specified more accurately, and this in turn has led to minor modifications in the results obtained from the aggregative data, but, whether the original or the modified parameters are used, comparison of the output from the two methods suggests that both yield the same ‘big picture’. Nevertheless, reconstitution has brought to light many previously unknown or obscure features of English population history, some of which are simultaneously illuminating and puzzling: illuminating because they enforce a revision of the received wisdom; puzzling because, although the existence of an unexpected pattern can be demonstrated, its explanation is unclear. The bulk of this essay is devoted to a possible explanation of one of the new findings of reconstitution, the rise in marital fertility which took place during the eighteenth century, for which no satisfactory explanation was offered in English population history . In a concluding section, the possible links between economic circumstances and population growth are discussed.
TL;DR: In this article, the authors present a modeling approach to address the issue that the distribution of services may respond to a conscious effort by public authorities or funding agencies to target areas with observed higher fertility.
Abstract: Most studies evaluating the impact of family planning on fertility treat the presence of family planning clinics as being “randomly” assigned among the areas included in the study. They tend to ignore the possibility that the distribution of services may be related to the fertility level observed in a particular area. In some cases the distribution of services may respond to a conscious effort by public authorities or funding agencies to target areas with observed higher fertility. Even in absence of program planning, the factors determining service placement might be related to the determinants of high, or low, fertility in a particular area. If that is the case, and one fails to account for the endogeneity of family planning services, then the estimated impact of family planning programs will be biased. This article presents a modeling approach to address this issue. The model extends the simultaneous equation framework by integrating an individual-level model of timing and spacing of children ...
TL;DR: A simple mathematical model of the decline in fecundity can be attributed to an increasing risk of fetal loss with maternal age is presented, and some preliminary laboratory results that support the model are presented.
TL;DR: It is proposed as a hypothesis that there may exist common aetiological factors for testicular cancer, low fertility and low offspring sex-ratio, and that a search for the causal factors involved may focus on agents that can act prenatally to disrupt the normal development and differentiation of the male reproductive organs.
Abstract: In the last few decades, the male proportion of newborn babies has been decreasing in several populations. The changes are very small and without practical importance per se, but the underlying biological mechanisms are not known. In the same period, testicular cancer incidence has increased, and there has been indications of decreasing sperm counts in men in several populations. The available knowledge on factors that influence the sex-ratio in humans supports the idea that an excess of girls in the offspring of a man may be an indicator of reproductive hazards. Data from a Danish case-control study show strong associations between testicular cancer, low fertility and a low M:F sex-ratio in the offspring. It is proposed as a hypothesis that there may exist common aetiological factors for testicular cancer, low fertility and low offspring sex-ratio, and that a search for the causal factors involved may focus on agents that can act prenatally to disrupt the normal development and differentiation of the male reproductive organs.