Thesis

Prenatal Exposure to Maternal Acculturative Stress: Effects on Maternal Cortisol and Hypothalamic-Pituitary-Adrenal (HPA) Axis Reactivity in Infants of Mexican Descent

Per the infant programming hypothesis, stressors occurring during the prenatal period may influence the development of the fetus resulting in long-lasting or permanent effects. Exposure to prenatal stress may negatively affect the maternal hypothalamic-pituitary-axis system and in turn the developing fetus’s hypothalamic-pituitary-axis (HPA) regulation. Research posits that atypical functioning of the HPA axis early in life may be associated with later development of depressive symptoms. Mexican-American mother/child dyads may be particularly vulnerable to fetal programming as women of Mexican descent experience high levels of psychosocial stressors, including stressors related to cultural adaptation such as acculturative stress—the stress associated with the acculturation process. Prenatal exposure to general psychological stressors increase maternal activation of the HPA-axis and stimulate the production of cortisol, which crosses the placental barrier to the fetus, resulting in increased fetal exposure to harmful stress hormones. Although the infant programming hypothesis is well supported in the literature, studies combining biological and cultural factors within a single model that address the transmission of acculturative stress from mother to infant and suggest a link between prenatal exposure to cortisol and fetal programming of the HPA axis are few. The present study investigated whether acculturative stress, along with maternal salivary cortisol levels, contribute to dysregulations in neonatal HPA axis activation in infants of Mexican descent. It was hypothesized that maternal acculturative stress would be associated with higher third-trimester maternal salivary cortisol area under the curve (AUC) and maternal acculturative stress would be associated with infant salivary cortisol AUC at birth. It was also hypothesized that maternal salivary cortisol levels would mediate the relationship between acculturative stress and infant salivary cortisol. Acculturative stress was neither associated with third trimester maternal salivary AUC nor infant salivary AUC at birth. In addition, maternal salivary AUC did not significantly mediate the relationship between acculturative stress and infant salivary cortisol at birth. Thus, the role of the prenatal period in the programming of mental health disparities in the Mexican-American population warrants further research.

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