Associations of maternal stress, gene expression, and newborn birthweight in the Democratic Republic of Congo.

Objectives: Maternal stress has long been associated with lower birthweight, which is associated with adverse health outcomes including many adult diseases. The underlying mechanisms remain elusive although changes in gene expression may play a role. Studies are only beginning to test how maternal stress impacts gene expression as reflected in the transcriptome. Materials and Methods: In a cohort of mothers and newborns in the eastern Democratic Republic of Congo (n=93), we studied the effects of four maternal stress measures (chronic stress, war trauma, sexual trauma, and general trauma) on the transcriptomes of maternal venous blood, newborn venous blood, and placental tissues, and on newborn birthweight. Maternal stress was investigated as independent measures, principal components, and clusters identified through machine learning. The transcriptome was assayed using the ClariomD chip. Multiple regression models were used to test for associations between maternal stress measures, the transcriptome, and newborn birthweight. Results: None of the maternal stress measures showed an association with expression of individual genes. In contrast, when testing global gene expression, war trauma was significantly associated with the placental transcriptome. War trauma was also significantly associated with birthweight in multiple models. Mediation analysis indicated that ~14% of the effect of war trauma on birthweight was mediated by a placental gene expression component. Discussion: Our results suggest that gene expression in the placenta, which represents the interface between mother and developing fetus, may partially mediate the negative impact of maternal stress on newborn birthweight.