|The goal of this dissertation is to identify the stressors faced daily by Kaqchikel Mayan women living in a rural community in Guatemala and investigate the association between stress and reproductive function among these women. The second chapter examines the relationship between self-reported concerns and urinary cortisol levels (a physiological stress marker). The third evaluates the link between daily variations in cortisol levels and fluctuations in the reproductive hormones: estrogen, progestins, luteinizing hormone, and follicle stimulating hormone during the menstrual cycle. The fourth chapter analyzes the association between maternal cortisol levels during the placentation period (first 3 weeks of gestation) and pregnancy fate. Daily Concerns reported by the participants included health problems affecting them and their relatives, inter-personal conflicts, work overloads, and economic problems, among others. These concerns were as a group a statistically significant predictor of increases in urinary cortisol levels (p = 0.03). Independently from those results, variations in cortisol levels were used to assess the combined effects of energetic, health, and psychosocial stressors faced by participants in their daily lives. Cortisol increases were significantly associated with untimely increases in the gonadotrophins throughout the menstrual cycle, with increased progestin levels during the follicular phase, and with low progestin and estrogen levels during the middle of the luteal phase (all p-values < 0.05). These hormonal variations are likely to impinge on ovulation, fertilization, and implantation (Soules, 1989; Baird et al., 1997; 1999; Ferin 1999; Wilcox et al., 1999). High cortisol levels were also associated with an increased risk of early spontaneous abortion (p = 0.03). These results are consistent with the hypotheses that stress can lead to the suppression of reproductive processes. The evolutionary hypothesis that motivated this research and the significance and implications of these results within that theoretical framework are discussed.