Maternal Factors Affecting the Integrity of the Late Gestation Placental Barrier to Murine Enterovirus Infection

Maternal factors that might impair the integrity of the late gestation placental barrier to enteroviruses were evaluated. Mice were inoculated with Theiler's murine encephalomyelitis virus (TMEV) on day 10-13 of gestation and sacrificed on day 16-18. Placentas and fetuses from dams with advanced age, forced daily swimming, short-term clamping of uteroplacental blood vessels, restricted dietary intake, or bacterial peritonitis were compared with tissues from TMEV-infected control mice. Increased maternal age, exercise, and malnutrition were associated with reduced fetal weight, and disturbed uteroplacental blood flow and severe malnutrition were associated with abnormal placental and fetal morphology. TMEV infection was observed sporadically by culture or in situ hybridization (or both) in fetuses from dams with interrupted uteroplacental blood flow, bacterial peritonitis, and older age but not in fetuses from control infected mice. This suggests that maternal factors, such as compromised uteroplacental blood flow, concomitant infection, and advanced age, may increase the risk of transplacental fetal infection.