Thbd^Pro/+ embryos and placentae are smaller than littermate Thbd^+/+ controls in pregnancies of FV^Q/QThbd^Pro/+ females mated to Thbd^Pro/+ males. The size distribution of Thbd^Pro/+ and littermate Thbd^+/+ embryos and placentae measured at 15.5 dpc is shown. Lengthwise cross-sectional area (A), length of the embryo (B), and placental cross-sectional area (C) were measured from digital photographs taken at a known magnification and resolution. P values were computed in comparison with Thbd^+/+ controls. No live Thbd^Pro/Pro embryos were obtained from these pregnancies; these die in utero before 12.5 dpc.