However, if a vaccine is inadvertently administered, the risk to mother and fetus should be lower than that from acquiring natural infection because the disease-causing virus has been attenuated (weakened) and is less virulent. Examples of vaccines that should not routinely be given to pregnant women include:
Measles, mumps, rubella (MMR) vaccine and its component vaccines are not recommended during pregnancy because of the theoretical risk to mother and fetus.
Measles illness is suspected to increase the risk of spontaneous abortion or premature delivery. Exposed women should be given measles immunoglobulin (purified antibodies to measles) within six days of exposure. MMR can be administered after delivery before hospital discharge if women are not immune to rubella or need a second dose of measles vaccine.
Mumps is not associated with fetal abnormalities during pregnancy, but if a pregnant woman contracts mumps in the first trimester the risk of spontaneous abortion is higher.
Rubella during pregnancy is associated with the development of a number of abnormalities in the fetus, including intellectual disability, deafness and heart defects, known as congenital rubella syndrome. No cases of this syndrome have been detected in women inadvertently vaccinated while pregnant or who became pregnant within 28 days of vaccination.
Should a pregnant woman inadvertently receive MMR vaccine, she should be counseled about the theoretical risk to the fetus. However, vaccination in pregnancy is not an automatic reason for termination of the pregnancy.
Varicella vaccine is not recommended for pregnant women. Varicella infection (chickenpox) in pregnant women is associated with an increased risk of pneumonia, often requiring admission to the hospital, and a small risk of limb abnormalities in the fetus. Newborn infants whose mothers acquire varicella within 5 days of delivery are at increased risk of acquiring severe varicella infection. Because of the increased susceptibility of mother and infant to harm from varicella infection, varicella immunoglobulin (purified antibodies to varicella) is recommended for exposed pregnant women within 96 hours of exposure and for exposed newborns within 48 hours of birth. While varicella immunoglobulin may not prevent varicella in all cases, it is likely to lessen the severity of the illness. Pregnancy in a household contact is not a reason to defer vaccination in a susceptible child. Pregnant women who do not have protection against varicella should receive the vaccine after delivery and a second dose four to eight weeks later. Varicella vaccine can be given after delivery before hospital discharge if women previously have not had chickenpox, have had only one varicella vaccine or have never received vaccine (a second dose can be given one month later).
Live, attenuated influenza vaccine (LAIV) should not be administered to pregnant women. The inactivated trivalent influenza vaccine (TIV) is recommended for all women (regardless of time in pregnancy) who will be pregnant during the influenza season.
Oral poliovirus vaccine (OPV) is not available in the United States and is not recommended for use in pregnancy. When exposure to polio is likely, pregnant women should receive the inactivated poliovirus vaccine [IPV].
Yellow fever vaccine should be administered to pregnant women only if travel to an endemic area is unavoidable and the risk of exposure is very high. The safety of this vaccine in pregnancy has not been established.
Typhoid vaccines have not been studied in pregnancy. One typhoid vaccine is composed of killed bacteria and given by injection. The other, an oral vaccine, is composed of weakened bacteria and should not be given to pregnant women.
Bacille Calmette Guerin (BCG) vaccine is used to prevent tuberculosis in some areas of the world. Although it has not been reported to cause harmful effects to the fetus, it is not recommended for use in pregnancy
Vaccinia vaccine (smallpox) has not been associated with fetal abnormalities. Smallpox infection causes more severe disease in pregnant than non-pregnant women. While routine vaccination in pregnant women is not recommended, the risks of clinical smallpox to mother and infant from clinical smallpox outweigh the risks of the vaccine.
