If you plan to become pregnant for the first time, you should check that you are immune to rubella (German measles) before becoming pregnant.

http://www.patient.co.uk/health/planning-to-become-pregnant

Rubella (German measles)
If you plan to become pregnant for the first time, you should check that you are immune torubella (German measles) before becoming pregnant. See your practice nurse for a pre-pregnancy blood test.