Overview
Why a Mild Maternal Illness Can Be a Fetal Emergency
Rubella is an enveloped, positive sense single stranded RNA virus in the Togaviridae family.
Rubella is an enveloped, positive-sense single-stranded RNA virus in the Togaviridae family. It spreads mainly through respiratory droplets. The mother may have only a brief, mild illness, but maternal viremia can carry the virus across the placenta and injure the developing fetus. The risk is greatest when infection occurs early in pregnancy, while fetal organs are forming. Congenital rubella syndrome can cause permanent sensorineural hearing loss, congenital heart disease such as patent ductus arteriosus or pulmonary artery stenosis, and eye abnormalities such as cataracts. Infection may also result in miscarriage or stillbirth. The mother’s relatively well appearance therefore cannot be used to reassure her about fetal risk. A pregnant individual who lacks documented immunity is the priority population for prevention. Immunity is usually acquired through previous vaccination or infection, but the record—not an assumption based on age or appearance—determines whether protection is documented.