If my rubella antibody titers were low during prenatal screening would they have told me?

I would ask: Generally it's part of routine screening rubeola isn't.

Yes, however: The best way to find out is to call your doctor and ask. If you have had a regular immunization schedule, you should be immune.The CDC has recently changed guidelines for immunization with MMR due to resurgence of the disease due to a significant number of unvaccinated persons in the US population. You can review those guidelines by going to www.CDC.gov.