Placental histology in hIGFBP-1 transgenic mice. (a) Gross morphology. The different functional layers of the mouse placenta are shown (d, decidual; j, junctional; l, labyrinthine). Differences in placental cross-sectional area and the relative proportions of the different functional layers of the placenta are clearly evident. (b) Decidual thickness. The thickness of the decidual layer is greater in placentas from wild-type females, indicating reduced trophoblast invasion in transgenic females. The labyrinthine zone is grossly enlarged, occupying approximately 80% of the cross-sectional area of the placenta compared with about 50% in wild-type placentas. sp, spongiotrophoblast; mv, maternal blood vessel; gc, glycogen cells; gt, trophoblast giant cells. (c) Trophoblasts in the junctional zone. The junctional zone is larger in placentas from transgenic females. There are similar numbers of glycogen cells and spongiotrophoblasts in placentas from wild-type females. In transgenic mice, spongiotrophoblasts are the predominant cell type; glycogen cells are relatively scarce compared with placentas from wild-type females.