Elevated pro-inflammatory gene expression in the third trimester of pregnancy in mothers who experienced stressful life events.

BACKGROUND: Stress exposure is associated with risk for adverse pregnancy outcomes, potentially in part through dysregulated immune and inflammatory activity. Evidence suggests that stress during pregnancy is associated with inflammation during pregnancy, consistent with risk for preterm birth. However, research has not tested whether complementary changes are reflected in immune cell gene expression, or upstream regulation of inflammation. The purpose of this study was to test associations between preconception and prenatal stress exposure and third trimester immune cell gene expression, focusing specifically on sets of genes previously linked to stress in non-pregnant samples: Pro-inflammatory genes, and antiviral and antibody genes.

METHODS: A sample of 116 low-income, diverse women was recruited from 5 U.S. sites by the Community Child and Health Network at the birth of a child. This study is of the subgroup of women who became pregnant again over the two-year follow-up period, and provided information on stressful life events that occurred both preconception and during the third trimester of the subsequent pregnancy. Dried blood spots (DBS) were collected in the third trimester of pregnancy, and used for gene expression analysis.

RESULTS: Women with more prenatal stressful life events had higher expression of pro-inflammatory genes when compared to those with fewer life events, and the effect was driven by increased activation of pro-inflammatory transcription factors, NF-κB and AP-1. Preconception stressful life event exposure was not associated with gene expression profiles. When entered into models simultaneously, only prenatal stressful life events were associated with up-regulation of pro-inflammatory genes. No differences between high or low stress groups emerged for antiviral or antibody genes.

CONCLUSIONS: Prenatal stress exposure was associated with up-regulated pro-inflammatory gene expression during pregnancy, and increased activity of NF-κB and AP-1. In contrast, stress occurring preconception was not associated with gene expression. These results are consistent with the hypothesis that stress-induced activation of pro-inflammatory transcriptional pathways in pregnancy, but not earlier, may increase risk for inflammation-driven adverse pregnancy outcomes.