A:The diagnosis of rubella is confirmed by serologic (blood) tests). An acute infection is confirmed by a significant rise in rubella antibody titre or by the presence of serum rubella IgM. Blood should be collected as early as possible (within 7–10 days) after onset of illness, and again 14–21 days (minimum of 7) days later. Rubella-specific IgM is found in virtually all infected patients by 3 weeks post development of a rash. Rubella-specific IgM is also found in 80% of post vaccination patients by 3 weeks. Congenitally infected infants will show an IgM response at 2-12 weeks postnatally. Rubella-specific IgM may persist for months after an acute infection and, possibly, after vaccination as well. False-positive IgM tests can be seen in persons with parvovirus infections, with a positive heterophile test for infectious mononucleosis, or with a positive rheumatoid factor. Elevated IgG rubella antibodies indicate a current or previous exposure/immunization to rubella. You should not worry. Get regular ultrasound done and be guided by your obstetrician.