Can the MMR vaccine cause birth defects?
The Measles, Mumps, and Rubella vaccine is a life vaccine, which means that while the virus in the vaccine is extremely weak it can cause disease, especially if the immune system of the person receiving the vaccine is compromised. For this reason, pregnant women should not have the vaccine unless there is a high risk of her getting one of the three diseases. It should be noted that vaccines that are made with dead viruses are completely safe for pregnant women. If in doubt ask your doctor.
