Showing papers on "Fertility published in 1989"

A cost of mating in female fruitflies

Abstract: COSTS of reproduction occur when an increase in reproductive rate reduces future reproduction by increasing mortality or reducing fertility. Such costs have been demonstrated in plants and animals in laboratory and field studies1–5. Their importance lies in their possible role in the evolution of life histories and of senescence6–15. An understanding of their mechanisms will also reveal the nature of the physiological constraints on longevity and fertility. Most accounts assume that these occur as a result of competition for nutrient allocation between growth, storage, somatic maintenance and reproduction16–21. An increase in reproductive rate would then result in a denial of nutrients to other processes, resulting in a drop in life expectancy or future fertility. Some support for this point of view comes from the finding that lifespan is lengthened in female Drosophila melanogaster that have inactive or absent ovaries22–23 or that are experimentally induced to produce fewer eggs24. Increased exposure to males, however, also results in a drop in lifespan24–26. We show here that mating with males greatly reduces lifespan in female fruitflies whose rates of egg-production and egg-fertility do not differ, suggesting both that simple nutrient allocation to reproduction is not its only physiological cost, and that males can cause females to remate at a frequency that results in reduced female lifetime reproductive success.

Can the fertility potential of a seminal sample be predicted accurately

Abstract: This paper highlights the most critical aspects of the problem of predicting fertility. To determine if a laboratory test(s) is highly correlated with fertility it is essential to have: a) specific, precise and accurate laboratory tests, and b) precise and accurate fertility data. Acquisition of precise and accurate data for laboratory tests and fertility of spermatozoa in the same sample is not easy. Data derived from in vitro fertilization are not tests of fertility, because only a subset of the attributes important for fertilization in vivo are tested. Because of deficiencies in fertility data, there probably is no valid report for human spermatozoa correlating results of laboratory tests and fertility, and very few valid studies for laboratory or domesticated animals. There is little doubt that objective measures of sperm motion, acrosomal status, or other characteristics are significantly correlated with fertility. However, establishment of the correlations between a group of attributes and fertility is not the question of interest. The goal is prediction of fertility. There has been no recent effort to develop a prediction of fertility or fecundity based on sperm characteristics, and achievement of this goal may be elusive.

Fertility reduction and the quality of family planning services.

Abstract: The purpose of this paper is to determine whether a focus on quality of family planning services is consistent with meeting demographic objectives. An analytical framework that links the six elements of quality with fertility is described. A review of existing literature and analysis suggest that improvements in quality of family planning services by enhancing the choice of contraceptive methods available in a country would increase the overall practice of contraception and thus would result in fertility reduction.

Fertility, Employment, and Child-Care Costs

Abstract: A sample of labor-market and birth histories is used to estimate the effects of child-care costs on employment and fertility decisions. A reduced-form empirical analysis is performed, which is based on hazard functions for transitions among various fertility-employment states. Higher child-care costs result in a lower birth rate for nonemployed women but not for employed women. Higher child-care costs also lead to an increase in the rate of leaving employment and a reduction in the rate of entering employment. The results suggest that potential behavioral effects of child-care subsidies could be significant and should be taken into account when alternative child-care policies are being debated.

Schooling, information and nonmarket productivity : contraceptive use and its effectiveness

Abstract: Information from two U.S. fertility surveys on couples knowledge about and use of specific contraceptives are used to estimate the technology of human reproduction in order to examine the association between schooling and productivity in the household sector. The results indicate that more schooled couples have a wider knowledge of contraceptive methods use more efficiently those contraceptive methods for which there is little information and large scope for misuse and are better able to mitigate the effects of their biological constraints (fecundity) on their fertility compared to less schooled couples. (EXCERPT)

Purchased child care, optimal family size and mother's employment: theory and econometric analysis.

Abstract: The paper develops a model of family size decisions in which couples choose explicitly a combination of mother's time and purchased childcare (e.g. childminders, nannies) for the care and rearing of children. The theoretical model implies that the impact of the mother's wage on her completed fertility varies with the market price of childcare, and that this effect increases (becoming less negative or more positive) with the level of her wage. Econometric analysis of British micro-data confirms the main predictions of the model.

Fecundity and natural fertility in humans.

Abstract: Natural fertility populations provide a benchmark against which one can gauge controlled fertility. The author bridges the gap between demographers who are interested in fertility and reproductive biologists who are concerned with the determinants of fecundity the capacity for reproduction. The delineation of fecundity enhances the ability to translate reproductive physicological research into predicted effects on fertility as well as the emphasis on fetal loss as a major component of previously unspecified onset of permanent sterility. Chapters cover the following topics: introduction patterns of natural fertility fecundity definition fecundability (fecundability and the distribution of fecund waits the empirical estimates of fecundability age and fecundability physiological determinants of fecundability a model of fecundability) fetal loss )expected number of fetal deaths length of gestation ending in loss duration of infecundability following each fetal loss and the total impact of fetal loss) the male contribution to fecundity and conclusions. Fecundity reflects a womans ability to conceive and her ability to carry the pregnancy to term. The components of the ability to conceive are 1) susceptability factors (menarche menopause lactational anovultion and pathological sterility) and 2) fecundability factors (net of coital frequency): length of ovarian cycles proportion of cycles ovulatory duration of the fertile period and probability of conception from a single insemination in the fertile period). The ability to carry a pregnancy to term is dependent on the 1) probability of fetal loss/conception length of gestation ending in fetal loss and the duration of residual infecundability following fetal loss. The paper examines how fecundity affects the age pattern of natural marital fertility. A homogeneous fecundity model is developed to show the relationship between fecundity total and the distribution of fecund waits a period between conceiving and conception with regular unprotected intercourse. However in a heterogeneous model it may be assumed that apparent fecundability varies according to Henrys beta distribution with human variation ranging from .14 to .31 and iwth adjustments for fetal loss .17 - .38. Heterogeneity increases expected fecund time to conception by about 50% or 4-9 months before conceiving. The age pattern of fecundability shows low levels in adolescence with a rapid rise to a peak of 25 years and declines thereafter due to coital frequency. The Wood and Weinstein model of fecundability with links to coitus physiology and the probability of conception is also discussed.

Evolution of low female fertility in plants: Pollen limitation, resource allocation and genetic load

Abstract: Some plant populations have low seed production, even when plenty of compatible pollen is supplied. Perennial species tend to have lower fertility than annuals, and outbreeders than inbreeders. The differences show up both in the proportion of flowers that produce fruits, and in the fraction of the ovules in those flowers that form seeds. Possible evolutionary explanations for low female fertility must be consistent with these observed patterns. One hypothesis is that low female fertility has evolved in long-lived organisms in which the costs of seed and fruit production are high - especially in outbreeders, in which there may be great costs to attracting enough pollinators to compete, in terms of male fertility, with other individuals in the population. Another possible explanation is mutational load, such that fitness is reduced by the mutations carried.

Long-term effects of testicular cancer on sexual functioning in married couples

Abstract: Long-term sequelae of testicular cancer have not been reported from the perspective of patient and spouse. As part of a larger study, both members of 34 married couples were interviewed individually, almost 4 years after treatment ended. Spouse and patient responses were compared for concordance (agreement) regarding psychosexual functioning and fertility issues. Wives perceived fewer long-term problems than husbands and were extremely supportive throughout their husbands' illnesses. At interview, whereas 23.5% of patients still felt less attractive as a result of treatment, no spouses shared this perception. Patients were more likely to report decreased, and wives increased sexual satisfaction compared to before cancer. However, both patients and spouses were more likely to report decreased frequency of intercourse than increased. In other areas as well, concordance was generally high. Few couples reported that infertility would pose a problem, but 53% were parents; men who banked sperm were less likely to already have children.

Is Routine Pre‐treatment Cryopreservation of Semen Worthwhile in the Management of Patients with Testicular Cancer?

Abstract: Post-treatment fertility was evaluated in 147 patients with testicular cancer, All had pre-treatment sperm cell analysis following orchiectomy during the years 1979 to 1987. For only 17 patients was the question of future fertility of no importance. Pre-treatment semen cryopreservation was requested by 91 patients, but poor semen parameters made this procedure impossible in 38. Of 99 evaluable patients, 44 had a post-treatment sperm count greater than or equal to 10 x 10(6)/ml and 22 of these fathered a child after treatment. Post-treatment fertility was observed to the same degree in patients who had pre-treatment semen cryopreservation as in those in whom this procedure could not be performed. Four of 53 patients used their deep-frozen semen but only 1 pregnancy resulted. The intensity of treatment, especially the extent of retroperitoneal surgery, had a significant effect on post-treatment fertility in the individual patient. Pre-treatment cryopreservation of semen may be psychologically useful in patients with newly diagnosed testicular cancer, but its clinical significance is doubtful.

Recent fertility dynamics in China: results from the 1987 One Percent Population Survey.

Abstract: There has been considerable speculation about the effects of Chinas economic reforms on recent trends in fertility. This article uses data from a 1987 survey the 1st detailed national-level data since the 1982 census and 1/1000 survey to analyze recent fertility change. The total fertility rate shows no overall trend since the late 1970s fluctuating around 2.4 children per woman. Sharp fluctuations in age distribution and marriage patterns render the crude birth rate an unreliable indicator. Parity progression ratios suggest that the overall trend has been toward slightly increasing numbers of 1-child families. Implications for policy and programs are discussed as are possible reasons for the halt of fertility decline at current levels. (authors)

Collecting data on pregnancy loss: a review of evidence from the World Fertility Survey.

Abstract: Estimates of levels and differentials of pregnancy loss are presented for 40 developing countries participating in the World Fertility Survey (WFS) program. Judged against agreed-upon levels of spontaneous loss in human populations, WFS surveys measured from 50 to 80 percent of recognizable losses. The coverage of induced abortions appears to be much worse. Consistent with data from other sources and settings, the probability of loss is strongly correlated with maternal demographic characteristics: age, pregnancy order, pregnancy spacing, and pregnancy loss history. Despite incomplete coverage, the WFS data on pregnancy loss provide considerable, and largely unexploited, insight on the dynamics of the reproductive career.

Efficacy of methods used to test fertility of beef bulls used for multiple-sire breeding under range conditions.

Abstract: A study was conducted during the 1982, 1983 and 1984 breeding seasons with 277 crossbred bulls, 1 to 3 yr of age, that were evaluated for physical soundness, testicular development, seminal quality, and both sexual and social behavior immediately before exposure to crossbred cow herds ranging in size from 89 to 329 cows. Crossbred cow herds were exposed to 4 to 24 bulls per breeding group (mean of 14) at a mean female: male ratio of 21.2 +/- .6:1 under extensive range conditions for 31 to 62 d (mean 46.6 d). All resulting calves were blood-typed to determine the number of calves sired by each bull as an estimate of his fertility. The mean number of calves sired by 1- (n = 116), 2- (n = 126) and 3-yr-old (n = 35) bulls was 4.7 +/- .1, 8.2 +/- .1 and 10.5 +/- .1, respectively. A regression model for predicting bull fertility under multiple-sire, range breeding conditions was selected that accounted for 29% of the total variance in fertility. Similar models accounted for a greater proportion of variance in fertility of 1-yr-old (37%) than of 2-yr-old bulls (22%). Due to the large amount of unexplained variation, the model could not predict individual bull fertility precisely. However, this study demonstrated that selection of herd sires with large scrotal circumference, low backfat thickness, low levels of primary sperm defects, and a low number of mounts in combination with a moderate number of services during libido testing would be expected to improve fertility of beef bulls used under extensive range conditions.

Fertility and fertility-related behavior among Mexican-American and non-Hispanic white female adolescents.

Abstract: Ethnic differences in fertility-related behavior are examined in a community-based probability sample of 706 Mexican-American and 317 non-Hispanic white females aged 13 through 19 years. Mexican-Americans are more likely than whites to have had a live birth, but are no more likely to have been pregnant and are less likely to have had sexual intercourse. Sexually experienced Mexican-Americans, however, are twice as likely as whites to have been pregnant. Among those ever pregnant, Mexican-Americans are more likely to have had a live birth, while whites are more likely to have had an abortion. Ethnic differences remain strong when socioeconomic status and indicators of social instability are controlled statistically, lending more support to the "minority status" hypothesis than to the "characteristics" hypothesis concerning the fertility-related behavior of minority group members.

Fertility in a male with trisomy 21.

Abstract: We review the published reports on reproduction in cases of non-mosaic trisomy 21 (Down's syndrome) and present the first fully documented case of a non-mosaic male with Down's syndrome fathering a pregnancy, a fact which has important implications in the light of caring for these people in the community.

Testis cancer: post-natal hormonal factors, sexual behaviour and fertility

Abstract: The relationship of risk of testis cancer, and subdivisions of the tumour by histology, to variables which may be related to hormonal status, sexual behaviour and fertility was investigated in data from a case-control study with 259 cases and 2 sets of controls. No consistent association was found between testis cancer risk and age at puberty, need to shave, obesity, alcohol intake, animal fat intake, and sexual behaviour. There was a significant excess of seminomas in very tall men. Testis cancer cases showed lower fertility than controls according to various measures, but this reflected the greater frequency of cryptorchidism among cases compared to controls. Among non-cryptorchid subjects there was no clear evidence that infertility was associated with risk of testis cancer.

OPINION: The relationship of abnormal semen parameters to male fertility

Abstract: To what extent do standard semen parameters reflect male fertility? A review of many studies over the last 35 years relating pregnancy rate to sperm counts in 'fertile' and 'infertile' couples indicates that standard semen parameters, though much maligned of late, are useful in evaluating the degree of 'male factor' in an infertile couple. However, 'male factor' is quite compatible with fertility in a couple if the wife is very fertile. Oligoasthenozoospermia is, unfortunately, for the most part, an untreatable condition. Yet, vigorous treatment of the wife may still result in pregnancy despite very poor semen quality. Higher sperm counts in an infertile couple are associated with higher pregnancy rates. But in the majority of infertile couples in whom the sperm count is poor, female factors also exist that prevent conception. If the wife were very fertile, she would have become pregnant despite her husband's oligozoospermia, and they would never have seen a physician for infertility. Thus, pregnancy can be achieved with very low sperm counts either by treatment of the wife, IVF, GIFT or ZIFT procedures.

The income--fertility relationship: effect of the net price of a child .

Abstract: This article examines the relationship between income and completed family size in empirical fertility models. The relationship, which is hypothesized to be positive, often is negative in empirical studies. This perverse result is thought to occur because of the many correlations between income and other factors that affect fertility. In this research, these other factors—such as the net price of a child, the opportunity cost of the wife’s time, and supply factors—are statistically controlled, and the income effect is positive and significant. When the net price of a child is not controlled, however, the income effect becomes negative and significant.

Polygyny and Fertility Among the Sereer of Senegal

Abstract: The population laboratory of Ngayokheme, in Senegal, has been observed longitudinally since 1962. Information on marital status at the time of birth (rather than at the time of a survey) is used to examine the effect of polygyny on fertility. Although plural marriages are less fertile and the rank order of the wife has an effect, the mechanism appears to operate through the age difference of the spouses and the greater likelihood of temporary separate residence in the case of polygynous marriages. An examination of birth intervals suggests that the lower fecundity of older men, rather than a reduction of the frequency of intercourse, is the main factor. However, there is little relation between the fertility of different wives of the same polygynists.

Occupational status and reproductive behavior in nineteenth-century Sweden: Locknevi Parish.

Abstract: This paper examined the effects of status as reflected by occupation on marriage fertility and survival of children in Locknevi parish Sweden. In the 1st generation (men married 1824-40) greater differences in the range of occupations existed than in subsequent generations. Mens reproductive patterns varied in concert with their occupational status. Little occupational mobility was apparent for men. This would suggest other things being equal that the reproductive differentials would accumulate over time. However by the 2nd generation in the sample during the period of apparent resource constriction in Locknevi Parish as land became scarcer and parcels became smaller reproductive differentials associated with occupation disappeared. Family size and rate of production of children decreased during this period as well. The pattern is consistent with Lockridges suggestion that the fertility transition occurred earlier than previously supposed in Sweden. In Locknevi it appears to have occurred as the result of elimination of reproductive differences previously associated with differences in resources. Although occupational correlations with reproduction disappeared after the 1st generation in this study differences associated with parity remained. sons received relatively more resources directly from fathers than did daughters. Daughters could gain access to resources from their husbands. The fact that womens lifetime fertility and number of children surviving to age 10 showed no major patterns with either fathers or husbands occupational status is of interest. (Authors modified).

Fertility policy and family planning in the Arab countries.

Abstract: An increasing number of Arab countries are instituting family planning programs to lower their populations' high fertility rates. This article examines Arab governments' perceptions of their countries' fertility situation, their desire to intervene in order to reduce or increase the rate of population growth, and the measures they have taken to influence the level of fertility. Special attention is given to family planning programs and access to methods of fertility regulation. A combination of stronger program effort and improved socioeconomic conditions account for much of the variation in contraceptive prevalence rates in 11 countries. Socioeconomic setting and political factors are found to be of primary importance in determining Arab fertility policies.

Epithelial ovarian cancer and combined oral contraceptives. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

Abstract: The relationship between use of combined oral contraceptives (OCs) and risk of epithelial ovarian cancer was investigated in a hospital-based case-control study conducted from 1979-86 in 7 countries. 368 women with histologically confirmed epithelial ovarian cancer were compared to 2397 hospital controls matched for age study center hospital and year of interview. The relative risk (RR) in women who had ever used combined OCs controlling for the confounding effect of number of pregnancies was 0.75 (95% confidence interval [CI] 0.56 1.01). The RR decreased with increasing duration of OC use and with increasing time since cessation of use. Except for mucinous tumors OC use was associated with a lower risk of all histological subtypes of epithelial ovarian cancer. While the reduced risk associated with OC use was present in parous women (RR=0.85) it was most pronounced in nulliparous women (RR-0.16). The magnitude of the negative association between OCs and ovarian cancer in 5 developing countries (RR=0.77) was similar to that reported in developed countries. (authors)

Early maturing Kipsigis women have higher reproductive success than late maturing women and cost more to marry

Abstract: Demographic analyses from 3 cohorts of Kenyan Kipsigis women married between 1940 and 1973 demonstrate that early maturing women have higher reproductive success than do late maturing women, due to longer reproductive lifespans and higher fertility. This result is independent of confounding effects of husband's wealth, but not of the wealth of a woman's parents which affects both menarcheal age and subsequent reproductive success. Data on bridewealth payments at 194 marriages occurring after 1959 show that men make higher marriage payments for early maturing women than for late maturing women. Together these results suggest that Kipsigis men vary their marriage payments in accordance with the reproductive value of their brides. The question of why men use age at menarche rather than bride's parents' wealth as a cue to their bride's subsequent reproductive performance is discussed in the light of changing social and economic conditions experienced by Kipsigis since the late 1920s.

A review: dietary restrictions on hunter-gatherer women and the implications for fertility and infant mortality.

Abstract: The relatively low reproductive rates of huntergatherer populations have been attributed to high natural mortality, low fertility, and cultural practices such as infanticide and sexual abstention. While we currently lack the data necessary to determine the relative effects of each of these factors on reproduction in any huntergatherer population, an analysis of the relations between cultural practices and reproduction at a more general level can set the stage for further research in huntergatherer societies. This paper reviews and discusses the current literature on specific links between female nutritional health, fertility, and infant mortality. It begins with a consideration of food taboos, one potential source of huntergatherer female nutritional stress. In particular, it is argued that the timing of food taboos on females in many huntergatherer societies often coincides with critical periods in women's reproductive careers. Next, the paper explores the interrelationships between female nutritional health and fertility and infant mortality, using data from modern huntergatherer and agricultural populations. Finally, because data adequate to test specific relationships between patterns of food restrictions and reproduction are not yet available, the paper concludes with a brief discussion of the data necessary for testing these relationships in huntergatherer populations.