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PubMed1984

Fertility and replacement: some alternative stochastic models and results for Brazil.

The observed joint distribution of births and child deaths for a cohort of women at a given point in time depends on the number of children that would have been born had the family experienced no deaths, the number of child deaths experienced, and the proportion of these deaths that are replaced by a subsequent birth. In this paper we estimate the parameters of the assumed distributions of these three events using a minimum distance estimation model and data from the 1970 Brazilian census. The parameter estimates are shown to be similar to those obtained previously using a maximum likelihood estimation model. When the data are subdivided according to women's years of schooling, estimates of probability of a child death and mean and variance of children born if no deaths decrease while estimates of probability of replacement of a dead child increase as years of schooling increase.

Adult↗
PubMed2005

The momentum of mortality change.

Mortality change is not usually assigned much importance as a source of population growth when future population trends are discussed. Yet it can make a significant contribution to population momentum. In populations that have experienced mortality change, cohort survivorship will continue varying for some time even if period mortality rates become constant. This continuing change in cohort survivorship can create a significant degree of mortality-induced population change, a process we call the 'momentum of mortality change'. The momentum of mortality change can be estimated by taking the ratio of e0 (the period life expectancy at birth) to CAL (the cross-sectional average length of life) for a given year. In industrialized nations, the momentum of mortality change can attenuate the negative effect on population growth of declining fertility or sustained below-replacement fertility. In India, where population momentum has a value of 1.436, the momentum of mortality change is the greatest contributor to its value.

Developed Countries↗
PubMed1986

Differences in the luteal phases after failed or successful in vitro fertilization and embryo replacement.

Luteal phases after in vitro fertilization (IVF) and embryo replacement have been studied in 241 cycles. A positive correlation was observed between the follicular estradiol (E2) peak and the progesterone (P) level on day 3 of the luteal phase, but no correlation was found between the E2-peak value and the luteal-phase duration or midluteal P concentration. When the trials were classified in relation to their outcome (i.e., clinical pregnancies, chemical pregnancies, or failures), the mean P level on day 3 of the luteal phase was significantly higher in clinical pregnancies than in chemical pregnancies and in failures. Mean E2 levels on day 3 were not significantly different among the three groups. Values of the E2/P ratio were significantly higher in chemical pregnancies than in the other groups. No significant differences were observed among the three groups on day 8. When comparing trials ending in failure to those leading to clinical pregnancy for the same patients, pregnancies were obtained in cycles in which early luteal P was higher and the early luteal E2/P ratio was lower than in failures cycles. These data suggest that high P levels and a low E2/P ratio in the early luteal phase might have a favorable influence on the implantation process in human IVF.

Embryo Implantation↗
PubMed1986

The use of synthetic culture medium and patient serum for human in vitro fertilization and embryo replacement.

The use of heat-inactivated patient serum as both fertilization and embryo replacement medium was compared in a prospective randomized study with a fully synthetic culture medium containing human serum albumin without serum addition (B3 INRA Menezo). Another series of the author's IVF program was analyzed retrospectively when a commercially available synthetic medium with bovine serum albumin (B2 INRA Menezo) or B3, as mentioned above, was used without serum addition for fertilization but with 50-100% patient serum as embryo replacement medium. Fertilization rates were significantly higher in the synthetic culture media (70%) than in serum (57%). The rate of polyploid fertilization was significantly lowest in B3 medium. There was a clear trend toward better pregnancy rates when high-percentage or 100% patient serum was used for embryo replacement, no matter if one, two, three, four or more embryos were replaced. We conclude that there should be no need for any kind of serum addition to fertilization media. The present study proves our previous observation that the use of serum seems to be beneficial as embryo replacement medium. This might well be explained by a "protein stick effect" due to the high macromolecular contents of serum rather than by viscosity measurements, since no significant increase in viscosity was observed when a high percentage of serum was added to culture media.

Blood↗
PubMed1988

Has Thailand's fertility decline stalled?

Thailand is 1 of the third world countries in which a very substantial fertility decline has occurred during the last 2 decades. However, there has been some recent concern, based on fertility rates derived from 3 national contraceptive prevalence surveys conducted in 1978/1979, 1981, and 1984, that the fertility decline may have lost momentum at a level well above replacement fertility. New evidence now available from a more recent national survey which permits calculation of retrospective fertility trends, in combination with those from registration data, clearly contradicts the suggestion of a fall in the fertility decline. Moreover, because expected family size remains low among women currently starting their reproductive careers and evidence shows that the preferred number of children has fallen more or less steadily, low fertility may be expected to be a feature of the Thai population for some time to come.

Asia↗
PubMed1990

The end of an affair? Geography and fertility in late post-transitional societies.

A common theme in the writings of population geographers with a fertility interest has been a concern with the convergence of interregional fertility differentials. It is now clear, however, that the widespread achievement in western societies of below-replacement fertility has resulted in a dramatic diminution of most forms of differential fertility, whether sectoral or spatial. The question of "what remains for the spatial analyst working in the traditional ecological mode?" must therefore be asked. An analysis of small-area fertility differentials in NSW in 1986 suggests (a) that most of the variability in local marital and total fertility is not statistically significant, and (b) that even if this problem is ignored, traditional ecological analysis has only trivial 'explanatory' power. While complete spatial uniformity is unlikely ever to be achieved, it is argued that the intrasocietal convergence of reproductive norms and behavior has proceeded so far that conventional geographic approaches to the analysis of fertility are unlikely any longer to be, if they ever were, fruitful

Australia↗
PubMed1992

Analysis of factors contributing to fertility decline in Korea.

With the successful Korean national family planning program and rapid socioeconomic advancement since 1962, the contraceptive prevalence rate has risen from 9% in 1964 to 79% in 1991, with the corresponding total fertility rate (TFR) going from 6.0 in 1960 to 1.6 in 1988, which is considerably below the replacement fertility rate. The main purpose of this study is, therefore, to identify the structural and causal factors that contributed to the fall in fertility over the last 3 decades, in an effort to formulate future population policy directions and strategies. The 2 methods used for the study were: the standardization approach to examine the structural factors on fertility decline, and the bongaarts model to measure the effects of the proximate variables in the fertility decline. The study indicated that the fall in the crude birth rate and the general fertility rate for the periods of 1960-70 and 1980-90 were largely influenced by the decline in marital fertility which was triggered by the national family planning program initiated in 1962. The analysis based on the bongaarts model revealed that the 3 principal factors which exercised a strong influence on the fertility decline were the rise in age at marriage, the increase in induced abortion, and the increase in contraceptive use, but the influence of induced abortion has been decreasing in recent years. In general, the study results suggest that the main concerns of the national family planning program should be shifted from the past quantitative approach with emphasis on fertility reduction to a qualitative approach which stresses maternal and child health and other public health programs.

Abortion, Induced↗
PubMed1987

World demographic trends. Population Division of the Department of International Economic and Social Affairs, United Nations Secretariat.

The world population almost doubled over the period 1950-1985. The rate of population growth, however, changed its course from the rise in the 1950s and 1960s to the decline in the 1970s and the first half of the 1980s, with a turning point around 1970. This is mainly due to the fact that significant fertility reduction started in many countries in Latin America and Asia during the period centred around 1970. The age structures of those countries became younger in the 1950s and 1960s, due to the considerable reduction in infant and child mortality, and then increasingly older in the 1970s and 1980s, mainly due to the fertility decline. Again, the turning point was around 1970. The proportion of population living in urban areas is increasing in most countries of the world. The level of urbanization is lower but the pace of urbanization is faster in the developing regions than in the developed regions. Africa has a different demographic profile from Latin America and Asia. Significant fertility decline has not started in the majority of countries in Africa, and mortality, although still very high, is declining particularly for infants and children, resulting in very high growth rates and increasingly younger age structures. In contrast, populations of the developed regions are characterized by low rates of growth, low levels of fertility and mortality, and an increasing proportion of older persons. A number of countries have below-replacement fertility levels and are projected to reach zero or negative population growth in the near future. This will reduce the proportion of the world population living in the developed regions from one-third in 1950 to one-sixth in 2025.

Age Factors↗
PubMed1985

The Philippine Population Program: an overview.

Since 1970 the Philippine population program has made considerable achievements in its effort to curb the country's high fertility rate. The program presently aims to attain a population growth rate of 2.0% in 1992 and eventually achieve replacement fertility for the country by the year 2000. To achieve these rates, the program has set into motion the so-called "high scenario" targets of greatly increasing the overall rates of use-effectiveness of program methods of contraception. The program continues to be guided by policies implemented since its start, as well as by new ones in resonse to recent developments. Though the program continues to receive funds from international donors, the Philippine government's share in the funding has steadily increased.

Asia↗
PubMed2004

Economic approaches to understanding families.

The economic approach helps explain the enormous changes in fertility, marriage, divorce, and human capital of families during the past 50 years. Large challenges remain to explain below-replacement fertility in over 60 countries and the consequences of such low birth rates for economic growth and other issues.

Divorce↗
PubMed2002

[Ecological restoration technologies for mined lands: a review].

Mining activities usually cause catastrophic and extensive environmental changes, and eventually cause major damages to the whole ecosystem. The natural restoration for mine lands and tailings is a very slow process, and even can hardly reach their original states. Therefore, how to develop rapid and efficient approaches to accelerate restoration of mined lands has been highlighted by restorationists and environmental engineers during the past two decades. Almost all studies in this field indicate that the major problems come from soils: such as high metal concentrations, extremely strong acidity resulting from oxidation of pyrite, and poor fertility. Replacement of topsoil is therefore regarded as the most efficient method to alleviate adverse conditions of substrates; if this method is not available, other alternatives with lime, fertilizers, organic manures, garbage, mining wastes, and others will be applicable. In the aspect of using plants, species with strong resistance and rapid growth, like grasses and herbaceous legume, are always the first choice. If utilizing plants for the purpose of phytoremediation, species that are capable of accumulating exceptionally high concentrations of phytotoxic metals and of course, have a huge biomass, are preferably considered. No matter what type of ecosystem a mined land is restored or reclaimed to, an evaluation on whether it is a successful restoration or reclamation should be given. However, more practical, simple, and universal evaluation methods as well as more cost-effective, and operation-easy restoration techniques are still waiting to be developed. A set of artificial restoration methods that can be widely applied was summarized, and a discussion on the advantage and disadvantage of several evaluation systems was conducted in this review.

Ecosystem↗
PubMed1990

Time and trajectory of convergence to population stationarity with immigration and low fertility.

"Recent research aimed at extending classical stable population theory to include immigration has shown that a stationary population is the long-term equilibrium outcome if, starting from any initial configuration, a population is projected forward under conditions of constant below-replacement fertility, constant mortality, and a constant annual number of immigrants whose age-sex composition is also fixed. This paper addresses two related questions: (1) What path does the projected population follow on its way to a long-term stationary population equilibrium? and (2) How long does it take for a stationary population to be achieved? To answer these questions a formal theory of population dynamics in the below replacement case is developed and then illustrated with a projection of the 1980 U.S. population."

Americas↗
PubMed1986

Projection of mean and variance functions for population processes with time-homogeneous laws of evolution.

This paper provides algorithms for projection of mean and covariance functions for stochastic population processes governed by time-homogeneous laws of fertility and mortality. The theoretical foundation of the algorithms is general age-dependent branching processes in discrete time. The algorithms are employed in several illustrative projections, based on 1982 Chinese data, of a population experiencing an abrupt transition to below replacement fertility. Methods of constructing confidence limits for total population size are illustrated. Also developed are procedures for projecting mean and variance functions for populations which may be heterogeneous with respect to mortality or fertility. The projections performed yield two observations. First, the coefficient of variation in population size appears to be inversely related to the Malthusian parameter of population growth. Second, the coefficient of variation for population size is negligible for large homogeneous initial populations. But when the initial population is heterogeneous with respect to fertility or mortality, then substantial coefficients of variation, exceeding 0.4, are observed in some of the projections performed.

Analysis of Variance↗
PubMed1984

The effect of time of initiation of clomiphene citrate on multiple follicle development for human in vitro fertilization and embryo replacement procedures.

Clomiphene citrate has been utilized for ovarian stimulation for human in vitro fertilization and embryo replacement (IVF-ER) procedures quite successfully. The optimal time and the amount of drug necessary for optimal development have not been identified. In this investigation, 58 patients participating in a human IVF-ER program were stimulated with clomiphene citrate, 150 mg/day for 5 days, beginning on day 3, 4, 5, or 7 of the menstrual cycle. Maximal numbers of oocytes recovered, fertilized, and transferred occurred when stimulation was initiated on the fifth day of the cycle. It is concluded that if clomiphene alone is utilized for multiple follicle development, cycle day 5 is optimal for drug initiation.

Adult↗
PubMed1985

Growth rate of follicular estrogen secretion in relation to the outcome of in vitro fertilization and embryo replacement.

Estradiol growth rate (EGR) during active follicular development was calculated for 89 stimulated in vitro fertilization cycles by exponential curve fit (r = 0.83). Cycles could be divided into four groups with very low, low, moderate, and high EGR values. Cases without oocyte fertilization and/or embryo replacement did not occur in the moderate EGR range, which also corresponded to a significantly better ratio of replaceable embryos versus oocytes recovered. This group was also endowed with a pregnancy rate amounting to 28.5% per laparoscopy and per replacement, i.e., about three times higher than in the three other groups. Very low or high EGR entailed significantly higher percentages of missed oocyte recovery and/or fertilization failure. The frequency of occurrence of a spontaneous luteinizing hormone peak was negatively correlated with EGR. The data indicate that a better outcome of in vitro fertilization may be expected when the estrogen rise starts early in the cycle and adopts a moderate growth rate (0.3 to 0.4).

Embryo Transfer↗
PubMedDate not supplied

Fertility determinants in Puerto Rico.

This paper examines the proximate determinants of fertility in Puerto Rico using data from a 1982 island-wide study. Contraceptive use was found to be the primary direct determinant of fertility in Puerto Rico, both for the total population and for each level of education studied. Female sterilization is the most prevalent method of contraception used in Puerto Rico at each educational level. Marriage is also important in Puerto Rico and is the only proximate determinant that varies across education groups. Late age at first marriage, in addition to high contraceptive use, accounts for the below-replacement fertility of women who have more than a high school education. In contrast, women who have not completed high school tend to marry early and not practice contraception for birth-spacing purposes. This study shows the advantages of analyzing fertility determinants at the population subgroup level (i.e., women of various educational attainment levels) so that the fertility of the total population can be better understood.

Adolescent↗