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Since the discovery of non-coding RNAs, several families of small regulatory molecules have been described including small nucleolar RNAs, piwi-interacting RNAs and microRNAs (miRNAs). MiRNAs are small single-stranded RNA molecules which play an important role in the regulation of gene expression at the transcriptional level. Recent studies demonstrated that about 30% of human genes are regulated by miRNAs and their deregulation has been associated with malignancies and poor outcome. Therefore, it is not surprising that profiling of miRNAs expression and studies on their regulation became a great field of interest in the last decade. However, miRNA-mediated regulation in pregnancy remains poorly investigated although several independent processes associated with placenta development have been shown to be miRNA-regulated. This review provides a general overview of the current data on profiles and functions of microRNAs in the peri-implantation period, embryonic stem cells, placentation and pregnancy, as well as in several pregnancy-related pathologies. We conclude that miRNAs present in the maternal circulation may provide a new promising diagnostic tool for pregnancy disorders.