The epidemiology of infertility: measurement, prevalence and an investigation of early life and reproductive risk factors

Estimated to affect one in six couples in the UK, infertility is an issue of great public health importance. This thesis provides a critical overview of the methodological issues in defining and studying infertility, and investigates the epidemiology of infertility, particularly prevalence and early life and reproductive risk factors. An initial literature review critically evaluated different approaches to defining and measuring infertility, and provided an overview of current prevalence, trends, and existing literature on the determinants of infertility. Two datasets were analysed for the investigation of the epidemiology of infertility. The first was the Uppsala Birth Cohort Study Multigen, which describes the experiences of over 6000 Swedish women born between 1915 and 1929. Two indicators of fertility were used: general and age-specific fertility rates, and time to first live birth. These were analysed with respect to specific early life factors: gestation, birthweight, birthweight for gestational age, and ponderal index. The results provide no evidence to support the hypothes is that these markers of inutero growth are associated with fertility in adult women. The second dataset was the National Women's Health Study, a population-based survey conducted in 2001 which collected information on the reproductive histories of over 7000 UK women. These data were used to describe the epidemiology of infertility in the UK, providing rarely reported data on the prevalence of infertility, help-seeking for fertility problems, and the use of treatment for fertility problems. The second stage of this work investigated the relationship between prior adverse reproductive outcomes and secondary infertility. The results suggest that secondary infertility is associated with prior adverse pregnancy outcome including termination, miscarriage and ectopic pregnancy, although with the exception of prior ectopic pregnancy, associations were weak and often inconsistent. The implications of these findings, and recommendations for future studies on infertility, are discussed.