Doctoral Dissertation Improvement: Fetal growth, developmental trajectories, and adult reproductive function

Harvard University, Cambridge MA

Investigators

Abstract

This study will look at patterns of prenatal and childhood growth, pubertal development, and adult reproductive function in a modern human population. Acknowledging that there is great variation in reproductive trajectories both within and among populations, the current study examines at what point during development these reproductive trajectories are established and what external factors shape them. Given recent evidence that early development can have profound and irreversible effects on adult anatomy and physiology, the general hypothesis is that reproductive trajectories may be initiated in childhood, or even prenatal life. More specifically, it is hypothesized that a number of factors, from age at reproductive maturation to menstrual regularity are influenced by prenatal and early postnatal growth rates. Most importantly, this study examines variation in adult gonadal steroid hormone levels, predicting that these profiles have strong developmental components. This two part project will use longitudinal data from Norway to address these hypotheses. The first part will focus on the relationships among perinatal growth, childhood development, reproductive trajectories, and ovarian function in a group of cycling women. A second, corresponding study will examine early growth, reproductive history, and testicular function in a cohort of men. It is predicted that in both sexes, size at birth and postnatal growth will be related to adult reproductive hormone profiles and reproductive histories. Both portions of this project will be extensions of ongoing epidemiological studies. For each female subject, an ovarian steroid profile has already been created based on radioimmunoassay (RIA) of saliva samples collected every day for an entire menstrual cycle. Gonadotropin levels and testosterone levels (in male subjects) have been measured in serum samples. Subjects of both sexes have previously filled out extensive questionnaires on health and lifestyle, which will be supplemented, in the current study, by ancillary interviews on living conditions during childhood and reproductive history. The birth and childhood growth records of all subjects will be obtained through national registries and/or the subjects themselves. From the perspective of reproductive ecology and physical anthropology, a greater understanding of the long-lasting effects of early life events may help to further explain the broad range of human variation and the remarkable plasticity humans show in response to both short-term and long-term changes in the environment. The current study also has obvious clinical and epidemiological implications, including the potential impact of early growth on fecundity and reproductive cancer risks. Not only will this study promote graduate training and research but it will foster international and interdisciplinary collaboration with researchers at the University of Tromso, Norway. The results of this project will be published in peer-reviewed anthropological and epidemiological journals in order to disseminate the findings and their potential implications to a wider audience.