Rubella - a cause of prenatal infection
Primary rubella infections in the early stages of pregnancy bear a high risk of foetal damage or multiple defects such as retinopathy, glaucoma, inner ear defects or aortic stenosis.

During the viraemic phase the infection rate is 80-90% for the placenta and 60-70% for the embryo. The number of cases of rubella embryopathy is about 100 per 800,000 live births.

Guidelines for diagnostic investigation
The Rubella reference centre of the Robert Koch Institute/Germany has published clear guidelines for determining immune status, detecting or elucidating primary and re-infections, and prenatal diagnosis (if requested, it will be provided).

Diagnostic investigation during pregnancy
The serious consequences of a primary infection occurring in a sero-negative woman, makes Rubella testing an essential element of routine antenatal care.
In the case of suspected infection in early pregnancy, interpretation of serological findings focus on identification of a primary infection, as such cases demand appropriate precautionary measures or therapeutic intervention.

Investigation of acute cases
The best indicator of a primary infection is the appearance of Rubella antibodies for the first time. For this event to be identified, the previous immune status must be known to have been sero-negative. A positive IgM test is indicative of an acute infection

Avidity measurement offers an additional supporting means of distinguishing between a primary and secondary infection. The index of IgG antibody level with and without urea in wash buffer is a measure of low and high avidity antibodies. Low indices are suggestive of a primary infection.
The IgG tests used for this purpose are quantitative and should be calibrated against the WHO standard.

Assessment of activation/re-infection/re-activation
Quantitative rubella IgG determinations are assuming an increasingly important place in the assessment of immune status. IgM antibodies are evaluated by means of index readings.
Determination of IgG titer and significant rises in titer on subsequent measurements offer another resource for improving the diagnosis of CMV infections and re-activations.

Supplementary investigations to exclude or to confirm an active infection are recommended.

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