Center for disease control and prevention: Travel notices: June 19, 2013
Special Advice for Pregnant Women
Talk to your health care provider if you are pregnant:
Before traveling to Poland, all pregnant women should talk with their health care providers to make sure they are protected against rubella and if it is advisable to travel.
Pregnant women who are not protected against rubella either through vaccination or previous rubella infection should avoid traveling to Poland during this outbreak. This is especially important during the first 20 weeks of pregnancy.
MMR vaccine is contraindicated during pregnancy.
When rubella infection occurs during early pregnancy serious consequences—such as miscarriages, stillbirths, and a severe birth defects in infants (Congenital rubella syndrome, CRS) can result. As many as 85 of 100 babies born to mothers who had rubella in the first 3 months of her pregnancy will have a birth defect.
Source: CDC travel notices: CDC / Rubella (German Measles) in Poland