Time to pregnancy--a model and its application
Boldsen, J.L.; Schaumburg, I.
Journal of Biosocial Science 22(2): 255-262
1990
ISSN/ISBN: 0021-9320 PMID: 2335546 DOI: 10.1017/s0021932000018587Document Number: 368669
Biological fertility is poorly measured by the number of children born in industrially advances societies. The deliberate intervention in human reproduction in many European countries has led to a declining fertility that is no gauge on the ability to reproduce which is of considerable epidemiological interest. Time to pregnancy can be collected in broad categories in large samples. A model condensing important information from such data is presented. In the model it is assumed that mean waiting time to pregnancy is constant for each couple but differs among couples, and that conceptions take place in continuous time (i.e. conceive not only once in each menstrual cycle). The data analyzed consisted of 3 studies where subjects replied to the question 'for how long did you try to become pregnant before you succeeded?'. 2 studies involved Danish mothers who recently gave birth and 1 study questioned pharmacy assistants who gave birth to a single live-born child. The model presented fits several large samples of reported waiting times. It is shown that multiparous women conceive more quickly than primiparous women. The model fits short and moderate waiting times but not long and very long waiting times.