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PubMed1994

Recent evidence on trends and differentials in Bangladesh fertility: an update.

A comparison of contraceptive and fertility data for 1985-91 with data for 1983 shows that fertility has continued to decline in Bangladesh, in all segments of society. The magnitude of decline varied according to educational level, region and urban-rural locality. The percentage decline in total marital fertility rate was somewhat higher among urban than rural residents; educated women showed greater declines than uneducated, increasing the overall educational differences in total fertility by 1991. Factors contributing to the recent decline in fertility are discussed.

Adolescent↗
PubMed1985

The fertility transition in nineteenth-century England and Wales: a social class model?

"The changing relationship between fertility and the standard of living is examined in the long term. The model presented provides a means of focusing on the cross-sectional association between fertility, especially marital fertility, and social class during the nineteenth-century fertility transition in England and Wales. An inverse relationship is revealed by all four of the perspectives adopted, but the problems inherent in defining social classes and the significance of fertility behaviour particular to occupations diminish the value of very broad generalizations."

Birth Rate↗
PubMed1995

[A comparative study on fertility transitions in China and Taiwan in historical perspective].

"Mainland China and Taiwan have both successfully undergone remarkable transitions from high to low fertility in recent decades. Comparing the transitions of the two Chinese populations brings out striking similarities in the changes in age patterns of fertility, but distinctive contrasts between the trends and speed of declines.... An overview of the history of population dynamics in the past 500 years reaffirms the assertion that fertility and mortality rates in ancient China were primarily reflections of biological responses to population pressure on resources. The results of the regression analysis of this study demonstrates that this density-dependent relationship has gradually vanished as the deliberate control of fertility prevails in contemporary China and Taiwan. The prevalence of fertility control is in large part attributable in Taiwan to the rational response of the population to changes in economic and social conditions that favor fewer children while the size of families in China is largely prescribed by the government there." (SUMMARY IN ENG)

Asia↗
PubMedDate not supplied

Age patterns of fertility in Madhya Pradesh.

"The purpose of this paper is to analyse age-patterns of fertility in Madhya Pradesh [in India] based on district level estimates of aggregate measures of fertility data collected in 1981.... Four clusters of districts have emerged which reveal a clear zonal pattern in age-specific fertility rates in the state. These groups bring out high fertility rates in the north and north-western parts of the state, gradually declining toward the south-eastern zone. The author suggests that separate policies and programmes be evolved for each of the clusters of districts for the purpose of bringing about reduction in fertility and promoting family welfare in the state of Madhya Pradesh."

Asia↗
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↗
PubMedDate not supplied

Induced abortion and fertility.

Even in countries with high rates of legal induced abortion, contraceptive use and marital patterns nearly always have a greater impact on fertility levels than does abortion. As a rule, extremely high rates of abortion--three or more abortions per woman of childbearing age during the reproductive years--are required for the fertility-inhibiting effect of abortion to rival that of contraceptive use. Nevertheless, the absolute effect of abortion on fertility (defined as the amount by which the current total fertility rate, or TFR, would increase if no abortions were performed) is often substantial. In most of the countries examined, the TFR would have been from about 20 percent to nearly 90 percent higher than it actually was (other things being equal) had no induced abortions been performed. Among developed countries, the Soviet Union, Japan, Eastern European countries, Israel and the United States have the highest total legal abortion rates, ranging from one abortion to more than five abortions per woman of childbearing age during the reproductive years. Among the developing countries for which reliable data are available, South Korea, China, Cuba and Singapore have rates of about 1-2 abortions per woman of fertile age. However, a number of other countries in Latin America and Asia, for which the data are deficient, probably have equally high rates.

Abortion, Induced↗
PubMed1987

Recent trends in fertility and family formation.

"Australia's fertility has declined significantly since the 1950s, and has remained below the long-term replacement level since 1976. The current trend appears to be towards a further decline. This paper describes the patterns of the fertility decline in terms of age and parity of the mother, and the effect on recent fertility decline of the postponement of marriage and family formation. The implications of the continued decline in fertility on completed family size are studied by reference to fertility patterns of marriage cohorts."

Age Factors↗
PubMed1990

Determinants of rural and urban fertility differentials in Nigeria.

Whatever proximate variables are examined, their differential effects on rural and urban fertility are small. This indicates that no major disturbance has taken place in urban or rural reproductive norms. However, two possible reasons for the converging pattern of rural and urban fertility in Nigeria are identified. One is that urban mothers in the first half of the childbearing age range have higher fertility than their rural counterparts. The other is that breast-feeding and post-partum abstinence, which are the major determinants of marital fertility, exert a more depressing influence on rural than urban fertility.

Adolescent↗
PubMed1996

The fertility transition in Cuba and the Federal Republic of Korea: the impact of organised family planning.

South Korea and Cuba are dissimilar in religion, economy, culture and attitudes toward premarital sexual relations. In 1960, Korea instituted a national family planning programme to combat rapid population growth. Cuba explicitly rejected Malthusian policies, but made family planning universally available in 1974 in response to health needs. Both countries have undergone rapid fertility declines and today have less than replacement level fertility. Both countries have also used a similar mixture of methods, including a high prevalence of female sterilisation. Abortion has played a major role in the fertility decline of both countries, rising in the first half of the fertility transition and then falling, although remaining a significant variable in the second half. It is concluded that access to contraception, voluntary sterilisation, and safe abortion has a direct impact on fertility and has been associated with a rapid fall in family size in two very different countries.

Birth Rate↗
PubMedDate not supplied

A causal approach to the study of fertility and familism.

This paper tests, within the framework of LISREL, the causal structures of fertility using data from the 1973-74 Growth of Alberta Family Study (GAFS) of women aged 18-44 who are currently married or living common-law. Differential fertility among two groups of women classified by nativity also are examined. The women's background characteristics (e.g., age, religiosity, and education) are viewed as exogenous variables. The endogenous variables are familism and expected family size; familism is designated as an intermediate variable in the model, linking demographic and socioeconomic (including cultural) factors to fertility, The results indicate that familism acts as an important variable explaining fertility, particularly, among foreign-born women. The study confirms and extends earlier research findings that religiosity and education influence couples' fertility, the former positively and the latter negatively.

Adolescent↗
PubMed1990

[A study on the proximate determinants of fertility decline in China].

To study the biological and behavioral process of the recent drastic fertility decline in China, the authors reviewed relating factors (proximate determinants) and applied the Bongaarts model to the population of China for the years 1971 and 1981, during which the fertility rate dropped most rapidly and substantial population control policies were performed. By application of the model, the decrease of TFR of 2.78 between 1971 and 1981 was estimated to be contributed by widespread of contraception (68%), later marriage (49%), and increase of induced abortion (28%), through shortening of the length of postpartum breastfeeding showed negative effects (-32%), on the assumption that local data could be substituted for some national data. Compared with other countries, China was characterized by coexistence of strong fertility-inhibiting effects of nonmarriage, contraception, induced abortion, and relatively strong fertility-inhibiting effects of breastfeeding. It strongly suggested that the fertility transition in China was realized by powerful population policies in the context of insufficient socioeconomic development to lead to the transition.

Abortion, Induced↗
PubMed1988

[Fertility decline and consequences of the National Family Planning Program: an analysis of the achievements of family planning activities in Chiang Mai and Lamphun provinces].

Based on the census data of 1970 and 1980 for each province of Thailand, the present study has revealed that between 1960-1980, a rapid fertility decline took place in 17 northern provinces and 26 central provinces of Thailand. A similar rapid fertility decline also took place starting in 1975 in the 16 northeast provinces and in the 14 southern provinces. Levels and trends of fertility found in this study suggest that most of the districts in the northern and the central regions reached the replacement level or below by 1985, and that similar levels will be attained by 1990 for almost every district in Thailand. This paper also stresses the impact of the rapid fertility decline on development in Thailand during the past 20 years, and its consequences. Lastly, the present study suggests that, for the future, the most important step is to understand well the consequences of this astonishing rapid fertility decline. This knowledge will be vital for the country and its people.

Asia↗
PubMed1986

["Delayed" modernization: spatial aspects of marital fertility decline in the federal provinces of Tyrol and Vorarlberg in the 1960s and 1970s].

"This study treats the decline of marital fertility in all of the 374 municipalities ('Gemeinden') of the Alpine area of western Austria (the Federal Provinces of the Tyrol and Vorarlberg). For each municipality Coale's Index of marital fertility (I(g)) is calculated for the years 1961-1971-1981. Particular attention is drawn to the geographical variation of the I(g)-values. A five-stage model is used to describe time-lag effects in the spatial fertility decline." It is found that "although there was a significant overall reduction in marital fertility of about 50%, most regional differences observed in 1961 can also be found in 1981." Economic, social, and religious factors related to these fertility trends are noted (SUMMARY IN ENG)

Austria↗
PubMedDate not supplied

Estimates of fertility levels in a rural community of Saudi Arabia.

There is a dearth of information on fertility levels in Saudi Arabia. In the absence of a reliable vital registration system, fertility level can be estimated from sample surveys. The Gompertz relational fertility model has been fitted to parity data on 923 women from a survey in the Al-Baha region. The estimated total fertility rate was 8.4. Education and age at marriage have strong association with the level of fertility. Those who married at early ages had higher parities, whereas women who had more than primary education reported lower parities.

Adolescent↗
PubMed1997

Spermatozoa lacking acrosin protein show delayed fertilization.

Acrosin (ACR), a serine proteinase located in the acrosome of the sperm, has been presumed to be involved in the recognition and binding of the sperm to the zona pellucida of the ovum and the sperm penetration through the zona pellucida. To examine the function of acrosin in vivo, we have generated mice carrying a mutation at the acrosin locus (Acr) through targeted disruption in embryonic stem (ES) cells. One chimeric male and female transmitted the targeted gene through their germ line. Homozygous Acr-/- mice are fertile and yield litters comparable in number and size to those of Acr+/+ mice. These data show that sperm of the homozygous Acr-/- mice are able to penetrate the zona pellucida, fertilize the ovum, and produce viable offspring. However, spermatozoa lacking acrosin protein show a delayed fertilization. One chimeric male which contained the targeted gene in 20% of its sperm transmitted only the Acr+ allele to its progeny. Furthermore, in vitro fertilization with equally mixed sperm cells of Acr+/+ and Acr-/- mice resulted in fertilization only with the Acr+ sperm cells. Incubation of oocytes with Acr+ or Acr- sperm show that the Acr+ sperm are faster to fertilize the oocytes than the Acr- sperm cells. These results suggest that Acr- sperm have a selective disadvantage when they are in competition with Acr+ sperm.

Acrosin↗
PubMed1998

Participation of sperm proteasome in fertilization of the phlebobranch ascidian Ciona intestinalis.

Sperm proteasomes are thought to be involved in sperm binding to and in sperm penetration through the vitelline coat of the eggs of the stolidobranch ascidian Halocynthia roretzi. However, it is not known whether they are involved in the fertilization of eggs of other ascidians. Therefore, we investigated whether sperm proteasomes are also involved in the fertilization of the eggs of the primitive phlebobranch ascidian Ciona intestinalis. Fertilization of the eggs of C. intestinalis was potently inhibited by the proteasome inhibitors MG115 and MG132 but not by the cysteine protease inhibitor E-64-d. On the other hand, neither fertilization of the vitelline coat-free eggs nor sperm binding to the vitelline coat was inhibited by the two proteasome inhibitors at a concentration sufficient to inhibit fertilization of intact eggs. These results indicate that the proteasome plays an essential role in sperm penetration through the vitelline coat rather than in sperm binding to the coat or in sperm-egg membrane fusion. The proteasome activity, which was detected in the sperm extract using Suc-Leu-Leu-Val-Tyr-MCA as a substrate, was strongly inhibited by both MG115 and MG132, and was weakly inhibited by chymostatin, whereas neither leupeptin nor E-64-d inhibited the activity. The molecular mass of the enzyme was estimated to be 600-kDa by Superose 12 gel filtration, and the activity in sperm extract was immunoprecipitated with an anti-proteasome antibody. These results indicate that the proteasome present in sperm of C. intestinalis is involved in fertilization, especially in the process of sperm penetration through the vitelline coat, probably functioning as a lysin.

Animals↗
PubMed1998

Fertilization of porcine oocytes following intracytoplasmic spermatozoon or isolated sperm head injection.

We demonstrated normal fertilization processes (as determined by pronuclear formation, pronuclear apposition and syngamy) in porcine oocytes either following intracytoplasmic spermatozoon (ICSI) or isolated sperm head injection. Microtubule organization and chromatin configuration were investigated in these oocytes during the first cell cycle. Following ICSI, the microtubular aster was organized from the neck of the spermatozoon and filled the whole cytoplasm. These male-derived microtubules appear to move both pronuclei to the center of oocytes. These cytoskeletal changes are analogous to those seen following conventional fertilization. In contrast, following isolated sperm head injection, the sperm aster was not seen. Instead, the microtubule matrix was organized from the cortex and then filled the whole cytoplasm in all cases in normally fertilized oocytes following injection (n=35). This organization is similar to what has been shown in the parthenogenetically activated oocytes. Chromosome analysis revealed that the oocytes injected with isolated sperm heads were fertilized normally. At 7 days following injection, the incidence of blastocoele formation following ICSI (38%) and isolated sperm head injection (22%) was higher than that following sham injection (2%). These results suggested that successful fertilization and preimplantation development occurred in porcine oocytes following either ICSI or isolated sperm head injection. Our results also indicated that fertilization processes can occur by self-assembled microtubules within cytoplasm in the absence of a sperm centrosome.

Animals↗
PubMedDate not supplied

Demographic consequences of unpredictability in fertility outcomes.

Child survival is probabilistic, but the unpredictability in family formation and completed family size has been neglected in the fertility literature. In many societies, ending the family cycle with too few or too many surviving offspring entails serious social, economic, or fitness consequences. A model of risk- (or variance-) sensitive adaptive behavior that addresses long-term fertility outcomes is presented. The model shows that under conditions likely to be common, optimal, risk-sensitive reproductive strategies deviate systematically from the completed family size that would be expected if reproductive outcome is were predictable. This is termed the "variance compensation hypothesis." Variance compensation may be either positive or negative, resulting in augmented or diminished fertility. Which outcome obtained is a function of identifiable social, economic, and environmental factors. Through its effect on fertility behavior, variance compensation has a direct bearing on birth spacing and completed fertility, and thereby on problems in demography and human population biology ranging from demographic transitions to maternal depletion and child health. Risk-sensitive models will be a necessary component of a general theory of fertility.

Birth Rate↗