Both pregs i was/am very low on my Rubella immunity (although I only just had a booster shot 14 months ago after the birth of my daughter....some people just don't retain it for some reason). My Dr has just said to be careful, especially for the first 12 weeks, to not be exposed to anyone with German measles (which is rather rare - but can cause a high incidence of abnormalities in babies if the mother is exposed). According to some research it recommends to be careful not to fall pregnant until 3 months after the shot.