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Egbert Te R Velde - One of the best experts on this subject based on the ideXlab platform.

  • ORIGINAL ARTICLE Reproductive epidemiology Too old to have children? Lessons from Natural Fertility populations
    2016
    Co-Authors: Marinus J. C. Eijkemans, Henri Leridon, Dik F. Habbema, Ken R. Smith, Egbert Te R Velde
    Abstract:

    study question: Is it possible to construct an age curve denoting the ages above which women are biologically too old to reproduce? summaryanswer:Weconstructed a curvebasedon the distribution of female age at last birth in Natural Fertility populations reflecting the ages above which women have become biologically too old to have children. what is known already: The median age at last birth (ALB) for females is 40–41 years of age across a range of Natural Fertility populations. This suggests that there is a fairly universal pattern of age-related Fertility decline. However, little is known about the distribution of female ALB and in the present era of modern birth control, it is impossible to assess the age-specific distribution of ALB. Reliable information is lacking that could benefit couples who envisage delaying childbearing. study design, size, duration: This study is a review of high-quality historical data sets of Natural Fertility populations in which the distributions of female age at last birth were analysed. The studies selected used a retrospective cohort design where women were followed as they age through their reproductive years. participants/materials, setting, methods: Using a common set of eligibility criteria, large datafiles of Natural Fertility popu

  • antral follicle counts are related to age at Natural Fertility loss and age at menopause
    Menopause, 2004
    Co-Authors: Frank J.m. Broekmans, Gabrielle J. Scheffer, Malcolm J Faddy, Egbert Te R Velde
    Abstract:

    Objective: The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events. Design: A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of Natural Fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman’s AFC relative to these percentiles. Results: The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause. Conclusions: The link between declining antral follicle counts and reproductively significant events like loss of Natural Fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.

  • antral follicle counts by transvaginal ultrasonography are related to age in women with proven Natural Fertility
    Fertility and Sterility, 1999
    Co-Authors: Gabrielle J. Scheffer, Frank J.m. Broekmans, Caspar W. N. Looman, Marinus Dorland, J.d.f. Habbema, Egbert Te R Velde
    Abstract:

    Objective: To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven Fertility. Design: Prospective observational study. Setting: Tertiary Fertility center. Patient(s): Healthy female volunteers with proven Fertility, recruited by advertisement in local newspapers. Intervention(s): The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles. Main Outcome Measure(s): Antral follicle count and total ovarian volume. Result(s): Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after Natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. Conclusion(s): The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.

Gabrielle J. Scheffer - One of the best experts on this subject based on the ideXlab platform.

  • antral follicle counts are related to age at Natural Fertility loss and age at menopause
    Menopause, 2004
    Co-Authors: Frank J.m. Broekmans, Gabrielle J. Scheffer, Malcolm J Faddy, Egbert Te R Velde
    Abstract:

    Objective: The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events. Design: A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of Natural Fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman’s AFC relative to these percentiles. Results: The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause. Conclusions: The link between declining antral follicle counts and reproductively significant events like loss of Natural Fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.

  • antral follicle counts by transvaginal ultrasonography are related to age in women with proven Natural Fertility
    Fertility and Sterility, 1999
    Co-Authors: Gabrielle J. Scheffer, Frank J.m. Broekmans, Caspar W. N. Looman, Marinus Dorland, J.d.f. Habbema, Egbert Te R Velde
    Abstract:

    Objective: To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven Fertility. Design: Prospective observational study. Setting: Tertiary Fertility center. Patient(s): Healthy female volunteers with proven Fertility, recruited by advertisement in local newspapers. Intervention(s): The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles. Main Outcome Measure(s): Antral follicle count and total ovarian volume. Result(s): Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after Natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. Conclusion(s): The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.

Frank J.m. Broekmans - One of the best experts on this subject based on the ideXlab platform.

  • antral follicle counts are related to age at Natural Fertility loss and age at menopause
    Menopause, 2004
    Co-Authors: Frank J.m. Broekmans, Gabrielle J. Scheffer, Malcolm J Faddy, Egbert Te R Velde
    Abstract:

    Objective: The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events. Design: A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of Natural Fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman’s AFC relative to these percentiles. Results: The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause. Conclusions: The link between declining antral follicle counts and reproductively significant events like loss of Natural Fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.

  • antral follicle counts by transvaginal ultrasonography are related to age in women with proven Natural Fertility
    Fertility and Sterility, 1999
    Co-Authors: Gabrielle J. Scheffer, Frank J.m. Broekmans, Caspar W. N. Looman, Marinus Dorland, J.d.f. Habbema, Egbert Te R Velde
    Abstract:

    Objective: To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven Fertility. Design: Prospective observational study. Setting: Tertiary Fertility center. Patient(s): Healthy female volunteers with proven Fertility, recruited by advertisement in local newspapers. Intervention(s): The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles. Main Outcome Measure(s): Antral follicle count and total ovarian volume. Result(s): Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after Natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. Conclusion(s): The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.

Bruce Winterhalder - One of the best experts on this subject based on the ideXlab platform.

  • the invisible cliff abrupt imposition of malthusian equilibrium in a Natural Fertility agrarian society
    PLOS ONE, 2014
    Co-Authors: Cedric O Puleston, Shripad Tuljapurkar, Bruce Winterhalder
    Abstract:

    Analysis of a Natural Fertility agrarian society with a multi-variate model of population ecology isolates three distinct phases of population growth following settlement of a new habitat: (1) a sometimes lengthy copial phase of surplus food production and constant vital rates; (2) a brief transition phase in which food shortages rapidly cause increased mortality and lessened Fertility; and (3) a Malthusian phase of indefinite length in which vital rates and quality of life are depressed, sometimes strikingly so. Copial phase duration declines with increases in the size of the founding group, maximum life expectancy and Fertility; it increases with habitat area and yield per hectare; and, it is unaffected by the sensitivity of vital rates to hunger. Transition phase duration is unaffected by size of founding population and area of settlement; it declines with yield, life expectancy, Fertility and the sensitivity of vital rates to hunger. We characterize the transition phase as the Malthusian transition interval (MTI), in order to highlight how little time populations generally have to adjust. Under food-limited density dependence, the copial phase passes quickly to an equilibrium of grim Malthusian constraints, in the manner of a runner dashing over an invisible cliff. The three-phase pattern diverges from widely held intuitions based on standard Lotka-Verhulst approaches to population regulation, with implications for the analysis of socio-cultural evolution, agricultural intensification, bioarchaeological interpretation of food stress in prehistoric societies, and state-level collapse.

  • The Invisible Cliff: Abrupt Imposition of Malthusian Equilibrium in a Natural-Fertility, Agrarian Society
    2014
    Co-Authors: Cedric O Puleston, Shripad Tuljapurkar, Bruce Winterhalder
    Abstract:

    Analysis of a Natural Fertility agrarian society with a multi-variate model of population ecology isolates three distinct phases of population growth following settlement of a new habitat: (1) a sometimes lengthy copial phase of surplus food production and constant vital rates; (2) a brief transition phase in which food shortages rapidly cause increased mortality and lessened Fertility; and (3) a Malthusian phase of indefinite length in which vital rates and quality of life are depressed, sometimes strikingly so. Copial phase duration declines with increases in the size of the founding group, maximum life expectancy and Fertility; it increases with habitat area and yield per hectare; and, it is unaffected by the sensitivity of vital rates to hunger. Transition phase duration is unaffected by size of founding population and area of settlement; it declines with yield, life expectancy, Fertility and the sensitivity of vital rates to hunger. We characterize the transition phase as the Malthusian transition interval (MTI), in order to highlight how little time populations generally have to adjust. Under food-limited density dependence, the copial phase passes quickly to an equilibrium of grim Malthusian constraints, in the manner of a runner dashing over an invisible cliff. The three-phase pattern diverges from widely held intuitions based on standard Lotka-Verhulst approaches to population regulation, with implications for the analysis of socio-cultural evolution

Cedric O Puleston - One of the best experts on this subject based on the ideXlab platform.

  • the invisible cliff abrupt imposition of malthusian equilibrium in a Natural Fertility agrarian society
    PLOS ONE, 2014
    Co-Authors: Cedric O Puleston, Shripad Tuljapurkar, Bruce Winterhalder
    Abstract:

    Analysis of a Natural Fertility agrarian society with a multi-variate model of population ecology isolates three distinct phases of population growth following settlement of a new habitat: (1) a sometimes lengthy copial phase of surplus food production and constant vital rates; (2) a brief transition phase in which food shortages rapidly cause increased mortality and lessened Fertility; and (3) a Malthusian phase of indefinite length in which vital rates and quality of life are depressed, sometimes strikingly so. Copial phase duration declines with increases in the size of the founding group, maximum life expectancy and Fertility; it increases with habitat area and yield per hectare; and, it is unaffected by the sensitivity of vital rates to hunger. Transition phase duration is unaffected by size of founding population and area of settlement; it declines with yield, life expectancy, Fertility and the sensitivity of vital rates to hunger. We characterize the transition phase as the Malthusian transition interval (MTI), in order to highlight how little time populations generally have to adjust. Under food-limited density dependence, the copial phase passes quickly to an equilibrium of grim Malthusian constraints, in the manner of a runner dashing over an invisible cliff. The three-phase pattern diverges from widely held intuitions based on standard Lotka-Verhulst approaches to population regulation, with implications for the analysis of socio-cultural evolution, agricultural intensification, bioarchaeological interpretation of food stress in prehistoric societies, and state-level collapse.

  • The Invisible Cliff: Abrupt Imposition of Malthusian Equilibrium in a Natural-Fertility, Agrarian Society
    2014
    Co-Authors: Cedric O Puleston, Shripad Tuljapurkar, Bruce Winterhalder
    Abstract:

    Analysis of a Natural Fertility agrarian society with a multi-variate model of population ecology isolates three distinct phases of population growth following settlement of a new habitat: (1) a sometimes lengthy copial phase of surplus food production and constant vital rates; (2) a brief transition phase in which food shortages rapidly cause increased mortality and lessened Fertility; and (3) a Malthusian phase of indefinite length in which vital rates and quality of life are depressed, sometimes strikingly so. Copial phase duration declines with increases in the size of the founding group, maximum life expectancy and Fertility; it increases with habitat area and yield per hectare; and, it is unaffected by the sensitivity of vital rates to hunger. Transition phase duration is unaffected by size of founding population and area of settlement; it declines with yield, life expectancy, Fertility and the sensitivity of vital rates to hunger. We characterize the transition phase as the Malthusian transition interval (MTI), in order to highlight how little time populations generally have to adjust. Under food-limited density dependence, the copial phase passes quickly to an equilibrium of grim Malthusian constraints, in the manner of a runner dashing over an invisible cliff. The three-phase pattern diverges from widely held intuitions based on standard Lotka-Verhulst approaches to population regulation, with implications for the analysis of socio-cultural evolution