Impairment of immunity during pregnancy and antiviral effect of amniotic fluid.

In 297 pregnant women serum-levels of antibody to rubella virus were determined by haemagglutination inhibition, and serum-levels of antibodies to herpes-simplex virus and Toxoplasma gondii were measured by indirect immunofluorescence tests. Sera of age-matched non-pregnant women with intrauterine devices were also tested for the antibodies. A lower level of humoral immunity was found in the pregnant women than in the controls, and this fell further as pregnancy progressed. Investigation of serum-samples taken at 14 weeks' gestation, at delivery, and 30-45 days post-partum revealed that after delivery humoral immunity to rubella virus returned to the levels of early gestation. Of 44 amniotic-fluid samples collected from pregnancies terminated at 11-14 wk and examined for antiviral activity to herpes-simplex virus and polio-virus, 7 exerted an antiviral effect which could be linked with the protein (other than alpha1-fetoprotein) fraction of the amniotic fluid.