The major and usually only clinical response to infection with PPV is maternal reproductive failure. Pathologic sequelae depend mainly on when exposure occurs during gestation. Dams may return to estrus, fail to farrow despite being anestrus, farrow few pigs per litter, or farrow a large proportion of mummified fetuses. All can reflect embryonic or fetal death or both. The only outward sign may be a decrease in maternal abdominal girth when fetuses die at midgestation or later and their associated fluids are resorbed. Other manifestations of maternal reproductive failure, namely, infertility, abortion, stillbirth, neonatal death, and reduced neonatal vitality, also have been ascribed to infection with PPV. These are normally only a minor component of the disease. The presence of mummified fetuses in a litter can prolong both gestation and the farrowing interval. Either may result in stillbirth of apparently normal littermates, whether or not they are infected.