Background Altered placenta miRNA abundance may impact the maternal-fetal interface and pregnancy outcomes . Understanding miRNA changes across gestation is essential before miRNAs can be used as biomarkers or prognostic indicators during pregnancy . Materials & Methods Using next-generation sequencing, we characterize the normative human placenta miRNA transcriptome in first (N=113) and third trimester (N=47). Results There are 801 miRNAs expressed in both first and third trimester, including 182 with similar expression across gestation (P≥0.05) and 182 significantly different (FDR <0.05). Of placenta-specific miRNA clusters, C14MC is more upregulated in first trimester and C19MC is more highly expressed overall . Conclusion This work provides a rich atlas of healthy pregnancies to direct functional studies investigating the epigenetic differences in first and third trimester placentae . Lay Abstract The human body produces microRNAs which affect the expression of genes and proteins . This study uses next generation sequencing to identify the microRNA profile of first and third trimester human placentae using a large cohort (N=113 first, N=47 third trimester). All pregnancies resulted in healthy babies . We identify microRNAs with significantly different expression between first and third trimester, as well as stably expressed microRNAs . This work provides a baseline for future studies which may use microRNAs to monitor maternal-fetal health throughout pregnancy.