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At least 19 recordsLinked to original sources

Individual fertility rate: a new individual fertility measure for small populations.

Fertility measurement in small preindustrial societies is hampered by small numbers and the lack of some essential data. Most measures of fertility are collective and require large enough populations to permit grouped data analysis. Existing individual measures of fertility are often unsatisfactory. This paper presents a new measure of individual fertility, the Individual Fertility Rate (IFR), which is constructed by dividing parity by reproductive span in years and multiplying the product by 100. The result is a number which may be used as a dependent individual or cumulative variable to study the effects of health and socioeconomic factors on fertility.

Adult

Measuring fertility demand.

We propose a multidimensional conceptualization of fertility demand and evaluate potential measures of each dimension, using data from a telephone survey of Wisconsin residents age 18-34. Most of the measures met tests for interval-level measurement; all produced high estimates of test-retest reliability. We found support for only two dimensions of demand, intensity and certainty; potential measures of centrality had relatively low associations with any of the latent dimensions. Demand certainty improved prediction of fertility expectations beyond a trichotomous (yes, no, don't know) measure, but demand intensity did not. We found mixed evidence for the conceptualization of fertility demand as a single continuum on which desire to avoid pregnancy is the opposite of desire to have a child.

Adolescent

Cigarette smoking and the outcomes of in vitro fertilization: measurement of effect size and levels of action.

OBJECTIVE: To assess whether cigarette smoking in women or men affects the outcomes of IVF-ET and at what functional levels smoking is active. INTERVENTIONS: Demographic and smoking data were collected by questionnaire at the onset of consecutive treatment cycles (n = 462) and at the time of ET. In addition to routine endocrine and clinical data, circulating immunoreactive inhibin, follicular fluid E2 endometrial thickness, and morphology were assessed. Reported exposure to cigarettes was validated using a serum cotinine assay. RESULTS: Serum cotinine level at the onset of treatment correlated strongly with the number of cigarettes reported (r = 0.68). The duration and dose of gonadotropin treatment was greater among active smokers than never smokers: 10.2 versus 9.2 days and 24.7 versus 19.8 ampules, respectively. Fertilization, pregnancy, and abortion rates were similar between groups. Multivariate analyses demonstrated negative correlation between female age, but no such effect was seen with female or male smoking. Sperm concentration was significantly reduced in male smokers (prewash: 108 versus 130 x 10(6); postwash: 17.1 versus 21.6 x 10(6)), although fertilization rate was unaffected (66% versus 62%). Follicular function, assessed using serum inhibin and E2, as well as follicular fluid E2 levels showed no significant difference between active smokers and never smokers. Endometrial thickness and morphology also were similar between groups. CONCLUSIONS: These data suggest that among couples undergoing IVF neither female nor male smoking has a measurable deleterious effect on conception rate. Female age remains a far more potent prognostic factor in the current study. However, when all the published data are combined, a significant deleterious effect of smoking on conception is suggested, with a common odds ratio of 0.540 (95% confidence interval 0.385 to 0.757).

Adult

Immunological control of fertility: measurement of affinity of antibodies to human chorionic gonadotrophin.

Four baboons were primed with diazotized beta human chorionic gonadotrophin and boosted with diazotized C-terminal beta human chorionic gonadotrophin peptide, and the changes in antibody amount and affinity determined using a double isotope modified Farr assay, using labelled human chorionic gonadotrophin as the antigen. The degree of cross-reaction with human luteinizing hormone was also determined. Although appreciable reactivity with luteinizing hormone was observed soon after immunization, this declined rapidly during the response. At the time intervals studied, there was a progressive increase in affinity of antibodies to human chorionic gonadotrophin until day 248 after priming. At day 313, in two of the animals, there was a decrease in affinity from 1.04 X 10(11) to 6.80 X 10(10) and 1.05 X 10(11) to 4.93 X 10(10) l/mol, whereas in the other two baboons there was a further increase in antibody affinity. At corresponding time intervals, there was a steady decrease in values of total antibody binding sites. To determine the overall effect of the maturation of affinity with a decrease in antibody amount on biological efficacy, the theoretical amount of chorionic gonadotrophin that would be neutralized was calculated. We computed that in all instances, over 99% of a peak concentration of chorionic gonadotrophin that could be in circulation in a pregnant baboon would be neutralized. This was in excellent agreement with results of mating experiments in these baboons. In over forty cycles studied, none of the matings resulted in a sustained pregnancy.

Animals

Computer modeling of human fertility: the impact of reproductive heterogeneity on measures of fertility.

As a result of the paucity of biological markers for both reproductive events and exposure to reproductive toxicants, it is likely that individual members of populations will be misclassified with respect to reproductive performance and xenobiotic exposure. A four-parameter computerized model of fertility (frequency of intercourse, male fecundity, female fecundity, and spontaneous abortion) was developed to explore the effect of misclassification of populations on several measures of fertility. The measures of fertility explored include cumulative percent pregnant, time to pregnancy, cycle specific fertility, and fecundability ratio. The cumulative percent pregnant and time to pregnancy appeared to be insensitive to small changes in reproductive competence. The fecundability ratio decreased in proportion to the size of population exposed to a reproductive toxicant. The three reproductive parameters, time to pregnancy, cumulative percent pregnant, and fecundability, do not appear useful as measures of reproductive heterogeneity in populations. The reproductive heterogeneity of a population was best defined by the change in cycle-specific fertility rate over the period of observation. These simulations suggest that the change in the cycle-specific fertility rate should be evaluated and comparable in all population groups over the period of observation to assure reproductive homogeneity.

Abortion, Spontaneous

Lifetime probability of additional births by age and parity for American women, 1935-1968: a new measurement of period fertility.

A new fertility measurement, probability that a woman of specified parity and age will bear a given number of births in her remaining lifetime, is proposed in this article. The measurement is a summary index of a set of age-parity-specific birth probabilities and in a particular case it is conceptually analogous to the total fertility by birth order but free from the influence of the parity distribution. Fertility of American women for the period 1935-1968 was studied by use of such lifetime probabilities. It appears that the trend of fertility of high birth orders has been parallel with that of low orders. Initiation of the recent decline in fertility depends on parity and age of woman.

Adolescent

Age, biological factors, and socioeconomic determinants of fertility: a new measure of cumulative fertility for use in the empirical analysis of family size.

To influence the number of children ever born to a woman, socioeconomic variables must operate through behavioral and biological mechanisms such as the age at marriage, the level of fertility in the absence of deliberate fertility control, and the level of control exerted to reduce fertility within marriage. In this paper, we propose a new measure of cumulative fertility which is standardized for the age-fecundity relationship and for exposure to the risk of conception associated with duration of marriage. A simple model of fertility behavior which incorporates some of the mechanisms through which socioeconomic factors may affect fertility is developed and applied to data from the United States to demonstrate the properties of alternative measures of family size. The results indicate that use of the new measure allows more precise estimates of socioeconomic fertility relationships than would be obtained with children ever born or by sample stratification.

Adult

A simple measure of fertility control.

We describe a simple measure of fertility control: the proportion of all births from the age-specific fertility schedule that occurs among women by age 35. This measure has broad applicability because it does not require information on marital fertility rates. When both the proportion of births by age 35 and the most commonly used measure of fertility control, m, are calculated for a population over time, they are correlated very highly. Because of increasing levels of nonmarital fertility in several developed countries, measures of fertility control that are based on marital fertility are less appropriate now than in the past.

Adult

[Fertility controls as the measure of herd fertility of dairy stock].

Hormonal analyses have been conducted along with intensive clinical following-up of the animals of three dairy herds in the area of Thessaloniki/Greece for a two year period. The data and progesterone profiles collected by means of milk progesterone assay (EIA) contribute considerably towards confirming and/or correcting clinical diagnoses. The clinical findings and the fertility parameters illustrate the considerable burden of fertility problems present in the dairy herds. The authors assume that faults in nutrition constitute the cause of silent heat and the problems derived from it. Faulty management is mainly associated with difficulties in oestrus diagnoses owing to disorders of fertility, failure to keep precise fertility data and the effects of inconsistent servicing of the cows on the part of the state inseminators.

Animals