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Theoretically the live attenuated virus in a vaccine could cross the placenta and result in viral infection of the fetus. Owing to this concern, most live attenuated vaccines, including the measles-mumps-rubella (MMR) and varicella vaccines, are contraindicated during pregnancy. Prospective controlled studies on women exposed to the rubella vaccine in the 3 months before conception or during the first trimester of pregnancy have reported no difference in pregnancy outcomes or malformation rates between the exposed and the nonexposed groups, and no adverse effects consistent with CRS.
In this study, the authors review and present data from studies on use of MMR, Varicella, Hepatitis and tetanus vaccines in pregancy. The report documents that exposure to either live or inactive vaccines during pregnancy has not been associated with an increased risk of adverse pregnancy outcomes, and no child to date has been born with CRS or varicella syndrome following rubella or varicella vaccination of the mother anytime during pregnancy. More details on the report are accessible at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093587/
ABSTRACT
Question: One of my patients is studying to become a dental hygienist. Owing to the program requirements, she received several vaccinations last week, including measles-mumps-rubella, varicella, and hepatitis B (HB) vaccines, as well as a tetanus booster. However, today a blood test confirmed that she is currently 6 weeks pregnant. What is known about the safety of these vaccines during pregnancy, and are there any general recommendations for vaccines for women who are planning to become pregnant or who are currently pregnant?
Answer: The combination measles-mumps-rubella vaccine and the varicella vaccine are live attenuated vaccines, and are contraindicated during pregnancy owing to theoretical concerns. However, there is no evidence that there are increased risks of malformations, congenital rubella syndrome, or varicella syndrome attributable to these vaccines. The HB and tetanus vaccines are composed of noninfectious particles or toxoids, and theoretically should cause no increased risk to the developing fetus. In addition, limited observational data also support no increased risk of any adverse pregnancy outcomes; consequently, administration of the HB and tetanus vaccines might be, if indicated, considered during pregnancy.
Women are sometimes exposed to live or inactive vaccines during pregnancy or shortly before conception. Although live vaccines are contraindicated in pregnancy, that recommendation is based on theoretical risk rather than evidence. Inactive vaccines pose no theoretical risk, and recommendations reflect this.