Macroscopic examination of E10.3 embryos. TFPI_K1 genotypes are indicated. Arrowheads, intra-yolk sac hemorrhage with red blood cells in yolk sac folds; arrow, blood “lakes” in yolk sac. Note that yolk sac hemorrhage can be found with a near normal embryo (left, bottom), suggesting that hemorrhage and concomitant circulatory collapse precede the wasting and ultimate death of the embryo.