Survival of Tfpi^+/+:Par4^−/−, Tfpi^+/−:Par4^−/−, and Tfpi^−/−:Par4^−/− pups from birth to wean. Litters were observed over the first 21 days of life. Dead pups were genotyped. Pups surviving through 21 days were weaned and genotyped. Shown is the percentage of survivors for each genotype over time.