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At least 19 recordsLinked to original sources
PubMed1992

Contributions of the proximate determinants to fertility change in Senegal.

The 1978 World Fertility Survey (WFS) and the 1986 Demographic and Health Survey (DHS) data are used to examine the relative contributions of three proximate determinants (nuptiality or marriage, contraception and post-partum infecundability) to fertility change in Senegal. The aim is to identify the important variables that is amenable for policy towards fertility reduction. Analysis shows that there are increases in the absolute measures of all three determinants. The magnitude of change is greatest in contraceptive use, moderate in marriage but least in duration of breast-feeding. However, the index of contraceptive use exerts the least impact on fertility reduction while that of post-partum infecundability makes the strongest impact on fertility. The impact of the nuptiality index on fertility change lies in-between contraception and breast-feeding.

Abortion, Spontaneous↗
PubMed1991

Handling of tubal infertility after introduction of in vitro fertilization: changes and consequences.

This study aimed at quantifying some important social and economic consequences of the altered handling of tubal infertility after the establishment of IVF treatment. The number of tubal operations was reduced by 50%. This had most important and positive implications on the availability of the operating theater for other elective operations, on the availability of hospital beds for other patient groups, and on the total duration of the certificate of illness. The calculated costs per live birth were $17,000 after tubal surgery, compared with $12,000 after IVF treatment. Life table analyses demonstrated a highly significant increased rate of deliveries after a complete IVF treatment (72.3% per patient) compared with tubal surgery (23.7%, P less than 0.001).

Adult↗
PubMed1992

Post-fertilization changes in Discoglossus pictus (Anura) eggs result in the formation of a capsular chamber where the egg rotates.

Discoglossus pictus is one of the few anurans with an egg where a capsular chamber forms as a consequence of fertilization; the egg with its vitelline envelope rotates in this chamber according to gravity. We investigated the formation of the capsular chamber through various experimental cytochemical and ultrastructural approaches, and found that it is the product of plug liquefaction. The plug is a lens-shaped jelly coat typical of Discoglossus, and covering only part of the egg animal half. About 15 min after fertilization, granular material coming from the egg enters the plug, which gradually dissolves and, once liquefied, reorganizes itself around the entire egg, thus forming the chamber. This process goes through stages of rearrangement of the 25-A- and 250-A-thick filaments which constitute the plug matrix. The material entering the plug derives from the exocytosis of two vacuole types, with electron transparent and granular PAS-positive contents. Liquefaction of the plug correlates with the reduction of disulfide bonds present in its matrix. Furthermore, in vitro tests showed that the substances released from the egg are active in selectively dissolving only the plug, and lose activity upon boiling.

Animals↗
PubMed1976

Changes in the topography of the sea urchin egg after fertilization.

Changes in the topography of the sea urchin egg after fertilization were studied by scanning and transmission electron microscopy. Strongylocentrotus purpuratus eggs were treated with dithiothreitol to modify the vitelline layer and to prevent formation of a fertilization membrane. Dithiothreitol treatment caused the microvilli to become more irregular in shape, length, and diameter than those of untreated eggs. The microvilli were similarly modified by trypsin treatment. This effect did not appear to be due to disruption of cytoskeletal elements beneath the plasma membrane, for neither colchicine nor cytochalasin B altered microvillar morphology. Thus, it appears that the vitelline layer may act in the maintenance of surface form of unfertilized eggs. Since dithiothreitol-treated eggs did not elevate a fertilization membrane, scanning electron microscopy could be used to directly observe modifications in the egg plasma membrane after fertilization. The wave of cortical granule exocytosis initiated at the point of attachment of the fertilizing sperm was characterized by the appearance of pits that subsequently opened, releasing the cortical granule contents and leaving depressions upon the egg surface. The perigranular membranes inserted during exocytosis were seen as smooth patches between the microvillous patches remaining from the original egg surface. This produced a mosaic surface with more than double the amount of membrane of unfertilized eggs. The mosaic surface subsequently reorganized to accommodate the inserted membrane material by elongation of microvilli. Blebs and membranous whorls present before reorganization suggested the existence of an unstable intermediate state of plasma membrane reorganization. Exocytosis and mosaic membrane formation were not blocked by colchicine or cytochalasin B, but microvillar elongation was blocked by cytochalasin B treatment.

Animals↗
PubMedDate not supplied

The U.S. fertility decline, 1961-1975: the contribution of changes in marital status and marital fertility.

Changes in marital fertility have accounted for 83 percent of the decline in total fertility since 1971; changes in marital status accounted for 19 percent, and changes in nonmarital fertility had only a negligible effect. Declines in the level of marital fertility account for a substantial part of the overall decrease; postponement of childbearing did not occur in any significant degree until the 1970s.

Adolescent↗
PubMedDate not supplied

Proximate determinants of fertility in Nigeria.

Data from the 1981-82 Nigeria Fertility Survey (NFS) are used to identify the key proximate determinants of fertility in Nigeria. The patterns of their individual and collective effects are analyzed in a search for possible sources of fertility change. Exposure to the risk of childbearing through first marriage is found to be the most important proximate determinant of Nigerian fertility. Subsequent to marriage, fertility is determined mainly by breastfeeding and postpartum sexual abstinence. Where fertility shows significant socioeconomic variations, there are equally identifiable patterns of the impact of the proximate determinants which explain these differentials to a large extent. On a national scale, the observed patterns of the impact of the measured proximate determinants do not appear to suggest that Nigerian fertility is soon to experience a large decline.

Adolescent↗
PubMedDate not supplied

Determinants of fertility decline in China, 1981: analysis of intermediate variables.

This study examines the proximate determinants of fertility in China by making use of the data collected by the One-per-Thousand Sample Fertility Survey of 1982. The results indicate that the most important inhibitor of potential fertility is deliberate control. Its contribution to fertility change has been far greater than all other proximate determinants. The marital structure of the population is also an important factor, while lactational infecundability and induced abortion are relatively unimportant. Comparative results by using data from the In-depth Fertility Survey conducted in Shanghai Municipality, Hebei and Shaanxi Provinces in April 1985 agree well in the ranking of the four intermediate factors. The findings point to successful family planning program and government population policies, which propelled the fertility transition to a substantial degree. Further research needs and policy implications of the results of the study are discussed.

Adolescent↗
PubMed1990

The growth of families headed by women: 1950-1980.

In recent decades, the number of families headed by women has increased dramatically. In this article, we use U.S. census data from 1950 to 1980 to consider the extent to which population growth, fertility change, decreased marriage, increased divorce, and increased household headship have contributed to the growth of female-headed families. For white women, the major source of growth during the 1960s and 1970s was an increase in the number of formerly married mothers due to increased divorce and decreased remarriage. There is a similar pattern for black women for the 1960-1970 period. During the 1970-1980 decade, however, the major source of growth for black women was an increase in the number of never-married mothers due to decreased marriage and increased fertility among nonmarried women.

Adolescent↗
PubMed1978

Fertility and family planning in rural northern Thailand.

From the mid-1960s to the mid-1970s, when fertility was declining in Thailand as a whole, especially rapid declines occurred in Northern Thailand, but they did not occur uniformly in all the region's provinces. The Northern Thailand Fertility Study, initiated in 1975 to study the reported fertility changes, gathered data in two provinces: Chiang Mai, where fertility decline has been quite rapid, and Chiang Rai, which experienced relatively little decline until 1974. This preliminary report discusses fertility levels and trends in the two provinces, fertility experience and expectations of respondents, attitudes toward and knowledge of family planning, and contraceptive practice. The results suggest that most of the difference in fertility decline is related to the different level of family planning program activity in the two provinces.

Abortion, Spontaneous↗
PubMed1990

Changes in timing of fertility--a Canadian experience.

This paper examines the patterns of timing of births of women using data from the Canadian Fertility Survey of 1984. Semi-Markovian schemes are applied to the maternity histories of the 5315 sample women in their reproductive ages in order to measure the intensity and timing of childbearing. Age-and-duration-specific transition probabilities are found to have substantially changed for the more recent birth cohorts compared to the older cohorts.

Adolescent↗
PubMed1990

Age at first marriage and fertility in rural Anhui, China.

This paper examines the changing nuptiality pattern of rural China, particularly rural Anhui in relation to the planned social changes since 1949 and their effect on fertility. The data are from the 1/1000 Fertility Survey of China, conducted by the Family Planning Commission in 1982. Before the family planning programme was introduced to rural Anhui (1972), the changing nuptiality pattern was indirectly affected by the planned social changes; after 1972, the substantial increase in age at first marriage was mainly due to the family planning programme. More recently, the centrally controlled social structure is loosening, due to the economic reform and the nuptiality pattern seems to join the 1972 trend, suggesting that the dramatic change of nuptiality pattern during the early 1970s to early 1980s was a temporary one. But its effect on fertility is clear, and the shortening interval between marriage and first birth may bring difficulties for future population control in rural China.

Adult↗
PubMed1990

Recent evidence on trends and differentials in Bangladesh fertility.

Recent data from Bangladesh reveal evidence of some fertility decline. Although fertility increased among younger age groups between 1975 and 1983, it was offset by a decrease in fertility in the older age groups, resulting in a slight overall decrease in total fertility in 1983. Fertility was lower among urban residents, educated mothers and contraceptive users than among rural residents, uneducated mothers and contraceptive non-users, respectively, particularly in 1983.

Adolescent↗
PubMed1991

A reversal of fertility trends in Singapore.

Free access to contraception and effective legislation measures, have resulted in a decline in fertility in Singapore. A new population policy of 'three children or more if you can afford it' was therefore introduced in 1986. This paper discusses the new population policies and measures their effect on fertility in Singapore.

Birth Rate↗
PubMed1990

Changes in fertility and the acceptability of pregnancies in northern Finland during the last 20 years.

The acceptability of pregnancies was studied in two birth cohorts in Northern Finland which represent 96% of all births in the region in 1966 (12,068 births) and 99% (9362 births) in 1985-1986. The numbers of women of fertile age in the area during these years were 148,000 and 158,000, so that fertility may be said to have fallen from 81 to 59 per 1000. The pregnancy was wanted in 63.0% of cases and unwanted in 12.2% in 1966, the rest being classified as accepted later. The corresponding figures in 1985-1986 were 91.8% and 1.0%. The latter figures changed very little when maternal age, parity and social class were standardized to the 1966 levels. Acceptability was connected with age, in that the age groups in which childbearing was most frequent, 20-25 years in 1966 and 26-30 years in 1985-1986, had the highest incidence of desired pregnancies. In spite of the fact that there were 1.4 times as many births per woman aged 15-49 years in the former cohort, more wanted children were born to the age group 25-34 years in the latter cohort. The percentage of wanted pregnancies also varied with the woman's parity, social class and marital status. The children in the 1966 cohort were followed until the age of 14 and the incidences of cerebral palsy (CP) and mental retardation (IQ less than 71) were 3.2 times higher among the unwanted children than among the wanted ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Legal↗
PubMed1992

Fertility in myotonic dystrophy in Saguenay-Lac-St-Jean: a historical perspective.

Myotonic dystrophy (MD) is an autosomal dominant disorder that has a high prevalence in Saguenay-Lac-St-Jean. A case-control study, based on a population register, of 373 MD patients who married in this region between 1855 and 1971 was conducted to determine whether their fertility was affected by the disorder. Six demographic parameters, that is the number of children, the age at marriage, the ages at the time of birth of the first and the last child, the interval between the marriage and the birth of the first child, and the interval between consecutive births, were analyzed. The mean number of children born to MD and control individuals was not different (P > 0.05). However, MD males had more children than MD females although they have started delaying their marriage since 1921. Fertility fell significantly in both the MD and control groups during the period of observation. This change reflects the decline in fertility of French Canadians in general during this period, but mainly after 1940.

Adult↗
PubMed1991

Patterns and change in Canadian fertility 1971-1988: first births after age 30.

An analysis of Canada's changing pattern of births during the period 1971-1988 suggests that the tempo and timing of fertility has changed. Between 1971 and 1988, the number and rates of first births to women in their 30s increased rapidly, and rates for women younger than 25 declined. The rate of first births (first births per 1,000 women) for women 30-34 increased from 11.5 in 1971 to 17.1 in 1981 and to 22.3 in 1988--a 94% increase over the 17 years. The rate for women 35-39 also rose from 3.0 in 1971 to 3.6 in 1981 and 5.9 in 1988--a 97% increase occurring mostly in the 1980s.

Adolescent↗