Hello, IgG antibodies remain for a life time after exposure previously, either through infection or vaccination. Presence of IgM antibodies indicates recent infection and these can persist for three months after exposure. If Rubella infection alone was the cause, your wife should not have aborted this time as she has been protected. Other causes should also be sought for in the current scenario. Please consult a specialist in high risk pregnancy before you plan next pregnancy to detect the cause of the recurrent abortions and plan further management. Hope this helps.