Influence of Pregnancy in Mice on the Course of Infection with Murine Poliomyelitis Virus

Pregnant mice inoculated with the Col. SK strain of murine poliomyelitis virus by the oral route showed a definite increase in susceptibility to infection as compared with non-pregnant female control animals. Beginning with the 4th day of pregnancy, mortality increased progressively and reached, with the last 4 days of gestation, a rate almost twice that of the control group. Immediately after parturition there was a rapid return of resistance to the non-pregnant level. The mechanism responsible for the greater susceptibility of the pregnant mouse does not seem to depend wholly upon alterations in the permeability of the intestinal mucosa during gestation, since a smaller group of mice infected by the intravenous route exhibited a similar increase in susceptibility.