Figure 5. P₄ delivery by Silastic implants fails to sustain pregnancy to full term.

(A) Average litter size of WT and KO+P₄ mothers. Litter size is presented as mean ± SEM; *P < 0.05, unpaired Student’s t test. (B) Representative photomicrographs of WT and KO+P₄ uteri on day 14 of pregnancy. Arrowheads and arrows indicate resorbing and normal IS, respectively. A representative H&E-stained section of resorbing IS from KO+P₄ uterus shows massive infiltration of blood cells. Scale bar: 200 μm. (C) Percentage of resorption sites in WT and KO+P₄ mice on day 14 of pregnancy. *P < 0.05, unpaired Student’s t test. (D) Cytokeratin staining of WT and KO+P₄ IS on day 14. Scale bar: 200 μm. dec, decidua; lab, labyrinth; sp, spongiotrophoblast.