Traditionally, it has been suggested that pregnancy causes an immunosuppressive state that would facilitate fetal tolerance and result in an increased susceptibility to infection. Although the suppression has been characterized as a global T-cell defect, the observation that the increase in susceptibility is restricted only to specific intracellular bacteria and viruses is consistent with a down regulation of only certain components of the innate immune system. Progress in the treatment and management of infections during pregnancy will require further understanding of the changes to the immune system that occur during pregnancy. It is hypothesized that there is a fundamental down-regulation in the innate immune system that occurs during pregnancy and remains until delivery and that changes in serum cytokines influence na(SqrRoot) ve CD4 differentiation to different subpopulations. To that end, this study will evaluate blood samples drawn from pregnant women during early, mid, and late pregnancy and post-partum for changes in the innate immune system and compare them to data on a similar cohort of women of childbearing age from an existing database of healthy, non-pregnant women. Changes in the cytokine profile, gene expression by microarray, and in the lymphocyte and natural killer (NK) cell populations will be identified. We may perform neutrophil analysis. We will evaluate toll-like receptors functionality, and any changes in PBMC throughout pregnancy.