We report here on a longitudinal study of stress and women's reproduction in a small Kaqchikel Mayan community in rural Guatemala. Current understanding of the effects of stress on the reproductive axis in women is mostly derived from clinical studies of individual stressors. Little is known, however, about the cumulative effects of "real life" stress. Cortisol increases in response to a broad variety of individual stressors (Tilbrook et al., 2002). In this article, we evaluate the association between daily fluctuations in women's urinary cortisol and reproductive hormones: estrone conjugates (E(1)C), pregnandiol glucuronide (PdG), luteinizing hormone (LH), and follicle stimulating hormone (FSH). To assess the association between daily changes in cortisol levels and changes in the profiles of the reproductive hormones, we used a random coefficients model based on polynomial regression. The sample includes 92 menstrual cycles provided by 24 participants over a year-long prospective study. Increases in urinary cortisol levels were associated with significant increases in gonadotrophin and progestin levels during the follicular phase. Also, in a time window between days 4 and 10 after ovulation, increased cortisol levels were associated with significantly lower progestin levels. These results are significant because untimely increases in gonadotrophins and low midluteal progesterone levels have previously been reported to impinge on the ovulatory and luteinization processes and to reduce the chances of successful implantation (Ferin, 1999; Baird et al., 1999). Future research should consider the possibility that stress may affect fecundability and implantation without necessarily causing amenorrhoea or oligomenorrhoea.
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