Abstract Objectives: We described the development of the main placental regions in a wild Brazilian rodent Necromys lasiurus. Methods: The volume fraction (VF) of different cell types which constitute the labyrinth was quantified by the one stop stereology using 31 placentae at different stages of gestation. In addition, we investigated the volume changes of the Lz, Jz, and Dd in samples of early gestation (10-11 days, n=3), mid-gestation (15-16 days, n=4), and near term (21 days, n=3) using the Cavalieri principle. 5 ?m sections were stained using H&E and fetal vessels were localized by immunohistochemistry using vimentin. Samples were analyzed using the Mercator® software and statistical analysis (one-way ANOVA and Mann and Whitney test) was performed using Graphpad Prism®. Results: There was a significant increase in absolute placental volume from early (4.427±0.282mm3) to mid-gestation (12.98±1.305mm3, p<0.01), followed by a reduction near term (7.52±0.155mm3, p<0.05). The absolute volume of the Lz, Jz, and Dd followed this same trend. The VF of the labyrinth components (fetal vessels, maternal compartment, giant cells and trophoblast) differed according to gestational age with a continuous increase in the proportion of fetal vessels from day 10 (7.38±0.49%) to 21 (34.05±0.876%, p<0.01) and in that of giant cells from mid- (11.66±0.286%) to late gestation (19.26±1.344%, p<0.01). In contrast, the VF of trophoblast decreased from mid- (37.29±1.013%) to late gestation (21.16±0.658%, p<0.01). There was no significant variation in the VF of maternal compartment throughout pregnancy. Conclusion: Although the placental volume in N. lasiurus is smaller than murine placenta, the dynamics of placental development appears similar between these rodents.