UC Berkeley

Demographers have long recognized that fertility patterns observed in populations are driven by both behavioral and biological determinants. Yet, most studies of contemporary fertility focus solely on the behavioral dimension, treating biology as a residual determinant, if mentioned at all. In this dissertation, I address this shortcoming by drawing from a biosocial framework that allows for the integration of biological measures into explanatory models of socio-demographic outcomes. In particular, I consider the interplay between reproductive biology and behavior in three empirical chapters on childlessness and subfecundity in the United States. In doing so, I demonstrate that biology can create a frame in which individuals make decisions across their reproductive life course.

In the first empirical chapter, I focus on the process of remaining childless as a case study for examining how women's reproductive choices and behaviors take place against the backdrop of changing social structures, competing preferences, and age-related declines in fecundity. Specifically, I focus on an understudied, yet revealing dimension of why individuals remain childless-- stated fertility expectations over the life course. Using data from the National Longitudinal Survey of Youth-1979 cohort, I use sequence analysis and logistic regression models to identify and describe groups of permanently childless women who follow similar trajectories of stated fertility expectations. Results indicate that three dimensions of fertility expectation patterns-- the emergence of a childless expectation, the consistency of childless expectations, and the types of patterns that precede a childless expectation-- provide a more nuanced description of the composition of permanently childless women than the standard voluntary/involuntary framework. The results, moreover, reflect how women reevaluate expectations for the future when they encounter critical junctures in their life courses.

The second empirical chapter considers how women internalize personal subjective risks about their fecundity, or their biological capacity to reproduce. First, I propose a conceptual model of perceived fecundity that emphasizes the evaluation of perceptions as a process drawn from understudied contextual and individual-level influences. Second, I use data from the National Longitudinal Survey of Youth (NLSY) 1997 cohort to provide new, nationally representative estimates of perceived fecundity among young adult women aged 25-30. Finally, I draw from the proposed conceptual framework to examine predictors of and variation in perceived fecundity. Results show striking variation across a range of demographic, contextual, situational, and experiential factors and highlight the need for improved measures of fecundity perceptions and a deeper understanding of how women evaluate their reproductive potential.

The third empirical chapter focuses on an understudied process by which reproductive biology can influence behavior. Prior research suggests that one reason women do not use contraception is because they perceive themselves to be infertile or have difficulty becoming pregnant (i.e. subfecund) and thus, at low risk of pregnancy. These beliefs, however, may provide a false sense of protection from unintended pregnancy if they are not medically accurate. Using data from the National Longitudinal Survey of Youth-1997 cohort, a large, nationally representative survey of young adults, I demonstrate that women with low perceived fecundity have higher odds of non-use of contraception. Further, these results persist after controlling for either a medical diagnosis of infertility or absence of pregnancy following at least 6 months of unprotected sex, suggesting that fecundity risk perceptions often operate independently of experienced subfecundity.