The main analysis in preparation for pregnancy
Rubella is a disease in which the key is not treatment, but prevention. In children and adults, it is mild, but infection in the first trimester of pregnancy leads to congenital rubella syndrome with severe heart defects, deafness and cataracts in the child. There is no specific treatment, so the only real protection is immunity acquired before pregnancy.
The IgG test answers the direct question: is a woman protected or not? A positive result with sufficient antibody levels means you have had rubella or the vaccination was effective and there is nothing to worry about. A negative or borderline result is an indication for vaccination before pregnancy, with mandatory protection for a month after vaccination.
The same analysis is used to check the effectiveness of vaccination one and a half to two months after its implementation, as well as when examining pregnant women who have been in contact with a patient with rubella: the presence of protective IgG in such a situation eliminates the question of risk to the fetus.
What do IgM and IgG mean?
The immune system produces different classes of antibodies at different times. Immunoglobulins M appear first, usually in the first or second week after infection, last for several weeks or months and then disappear. Their detection indicates an acute or recent process.
Immunoglobulins G appear later, after a few weeks, and persist for years, and often for life. They mean that a meeting with the pathogen took place in the past, and in many cases indicate formed immunity. Therefore, positive IgG in itself is not a reason for treatment.
Why dynamics are important, not just a number
A single result is often ambiguous. Antibody levels vary from person to person, with borderline levels falling into what is known as a gray area. A reliable sign of active infection is a fourfold increase in IgG titer in paired sera taken at intervals of 10–14 days.
This is why serology is rarely prescribed as a single test. The doctor either combines IgM and IgG, or repeats the test, or confirms the result with a direct method - PCR, which detects the DNA or RNA of the pathogen itself.
Limitations of the method
Antibodies do not appear immediately: in the first days of the disease, serology can be negative if the infection has already begun - this is the period of the serological window. In case of immunodeficiency and against the background of immunosuppressive therapy, antibodies may not be produced at all.
Cross-reactions with related pathogens are also possible, giving a false-positive result. Therefore, treatment is never prescribed “based on analysis” - only on the basis of a combination of clinical data and research results.