Time course of maternal circulating miRNA signatures associated to normal human pregnancy.

Emerging evidence has revealed alterations of microRNA (miRNA) profiles in peripheral blood associated to changes in a range of physiological conditions, suggesting that circulating miRNA profiles could be used as prognostic and/or diagnostic biomarkers for a wide variety of clinical conditions. Normal human pregnancy poses an extensive number of physiological challenges, affecting virtually every level of the pregnant woman s biology, as well as changing contributions of the placenta and fetus. In this cohort study, using longitudinal large-scale profiling of circulating miRNAs at four defined stages during and after normal pregnancy, relative to non-pregnant controls, we investigate temporal changes in miRNA profiles as potential biomarkers of pregnancy evolution. By comparing the profiling of blood plasma miRNAs with available expression data, we found that miRNAs most prominently expressed in key reproductive tissues are collectively down regulated throughout pregnancy. Furthermore, we find a bias in the proportion of differentially expressed miRNAs associated with fetal sex right from the first trimester. Lastly, by combining circulating miRNAs expression with fetal growth indicators derived from the same women, we identify a robust miRNA signature associated to fetal growth during normal pregnancy. Our results demonstrate the existence of temporal changes of specific miRNAs associated to distinct aspects of pregnancy, including correlates of placental function, fetal gender, and fetal growth, as well as an early lactation-related signature; strongly suggesting the potential of peripheral miRNAs as biomarkers of normal pregnancy.