Rubella
The clinical features and consequences of primary rubella in pregnancy are well established, and the unreliability of a clinical diagnosis of rubella is accepted.
The risk to the fetus of primary rubella in the first 16 weeks of gestation is substantial. Rubella infection prior to the estimated date of conception or after 20 weeks of gestation carries no documented risk. Primary rubella contracted between 16 and 20 weeks of gestation carries a minimal risk of deafness only.
A rubella reinfection is defined as rubella infection in someone who has previously had either documented natural rubella virus infection or successful rubella immunisation.
Rubella poses a particular problem because the organism persists in the host and continues to replicate and may cause tissue destruction after birth.
The possible long-term outcomes of infections acquired prenatally are:
- sensorineural deafness
- diabetes mellitus
- thyroid disease
- growth hormone deficiency
- vascular effects
- encephalitis.
As discussed, the main effect of parvovirus infection is fetal anaemia. The risk of transmission is increased between 9-20 weeks of gestation. Transplacental transmission risk is about 30%, depending on gestation.
Infection in the first 20 weeks of pregnancy can lead to intrauterine death and hydrops fetalis. Overall fetal loss rate for those with maternal infection is 5-10%. Current evidence suggests that parvovirus infection in pregnancy is not associated with long-term adverse effects in the infant.
Most infants treated by intrauterine transfusion because of parvovirus-related anaemia have been found to have normal neonatal outcomes. However, repeated transfusions can cause complications and close follow-up of infected fetuses who have received multiple transfusions is mandatory.