@article{b10ed01e97804bccb47a65c2ae3a2d78,
title = "A model of age-specific fecundability",
abstract = "A new model of the behavioural and physiological causes of age-specific variation in marital fecundability is presented. Total fecundability is decomposed into a series of susceptibility factors (the length of ovarian cycles, the length of the fertile period within each cycle, the probability that a cycle is ovulatory, and the likelihood that an act of unprotected intercourse within the fertile period results in conception) and an exposure factor reflecting the effect of duration of marriage on coital frequency. The impact of intra-uterine mortality on effective fecundability is also modelled. Data on western women, from which standard age curves of fecundability are estimated, suggest that any decline in fecundity between ages 30 and 40 is attributable to changes, not in the ability to conceive, but in the capacity to carry a pregnancy to term. Sensitivity tests suggest that the most important potential sources of inter-population variation in fecundability are intra-uterine death and the incidence of anovulatory cycles.",
author = "Wood, {James W.} and Maxine Weinstein",
note = "Funding Information: Although the theoretical importance of fecundability is beyond question, there are several difficulties in estimating it from direct observations. Fecundability is frequently estimated from the distribution of waiting times to conception, s However, observations on waiting times are typically censored at higher values, introducing systematic bias into the estimates. ~ Moreover, heterogeneity if fecundability among women is known to modify the simple inverse relation between fecundability and conception waits; unless strong assumptions are made about the distribution of fecundability among women, unbiased estimation of fecundability from waiting times becomes impossible. 7 For example, Goldman and her colleagues s have recently examined waiting times from marriage to first recognized conception, using World Fertility Survey data from a number of countries. In addition to several methodological problems, they discovered * An earlier version of this paper was presented at the Annual Meeting of the Population Association of America, San Francisco, California, April 1986. We thank Barbara Anderson, John Bongaarts, Benjamin Campbell, Peter Ellison, Henry Harpending, Albert Hermalin, John Hobcraft, Norman Ryder and Kenneth Wachter for comments and discussion. We also thank Paul Friday for his help in programming the model, and Joseph Tuorek and Sun Chang-Chern for assistance in preparing the figures. Supported by NICHD grant R01-HD-20989 and by a grant from the Andrew W. Mellon Foundation. t Department of Anthropology and Center for Demography and Ecology, University of Wisconsin, 1180 Observatory Drive, Madison, Wisconsin 53706. :~ Department of Demography, Georgetown University, Washington, D.C. 20057. C. Gini, 'Premieres recherches sur la frcondabilit6 de la femme', Proceedings of the International Mathematical Congress, 2 (1924), pp. 889-892. z A 'susceptible state' is one in which a woman can potentially conceive as a result of unprotected intercourse. This state thus excludes such conditions as pregnancy, lactational anovulation and pathological sterility. 3 M. C. Sheps and J. A. Menken, Mathematical Models of Conception and Birth (Chicago: University of Chicago Press, 1973), p. 65. 4 E. Perrin and M. C. Sheps, 'Human reproduction: a stochastic process', Biometrics, 20 (1964), pp. 28-45. 5 Sheps and Menken, loc. cit. in footnote 3, pp. 79-84. D. R. Cox and D. Oakes, Analysis of Survival Data (London: Chapman and Hall, 1984), pp. 4-5. 7 H. Majumdar and M. C. Sheps, 'Estimators of a type I geometric distribution from observations on conception times', Demography, 7 (1970), pp. 349-360. 8 N. Goldman, C. F. Westoff and L. E. Paul, 'Estimation of fecundability from survey data', Studies in Family Planning, 16 (1985), pp. 252 261.",
year = "1988",
month = mar,
day = "1",
doi = "10.1080/0032472031000143136",
language = "English (US)",
volume = "42",
pages = "85--113",
journal = "Population Studies",
issn = "0032-4728",
publisher = "United Nations Publications",
number = "1",
}