The topic of vaccinations during pregnancy is a common source of concern for expectant parents. Medical consensus confirms that certain immunizations are not only safe but highly recommended for both the mother and the developing baby. These recommended vaccines, which utilize inactivated (non-live) viruses or bacterial components, provide defense against serious infections. However, other vaccines that contain live, weakened viruses are contraindicated during gestation due to a theoretical risk to the fetus. Navigating these recommendations requires understanding how maternal vaccination provides protection and careful planning with a healthcare provider.
How Maternal Immunization Protects the Newborn
Maternal immunization provides newborns with temporary protection through passive immunity. When a pregnant person receives a vaccine, their immune system produces protective antibodies that circulate in the bloodstream. These antibodies are actively transferred across the placenta to the fetus, primarily during the third trimester. This transplacental transfer provides the infant with a defense system that begins working immediately at birth. Immunoglobulin G (IgG) is the antibody class that crosses the placenta most efficiently, offering systemic protection.
This passive immunity is important because a newborn’s own immune system is immature and cannot be vaccinated against many diseases until they are several months old. The maternal antibodies act as a protective shield during this vulnerable period. Protection generally lasts for the first few months of life, until the infant can begin their own scheduled immunizations.
Essential Vaccines Recommended During Pregnancy
The vaccines recommended during pregnancy are non-live vaccines, meaning they cannot cause the diseases they prevent. They are deemed safe and necessary to protect the mother from severe illness and to provide passive immunity to the baby. The two most commonly recommended immunizations are the Tdap vaccine and the seasonal influenza shot.
Tdap (Tetanus, Diphtheria, and Pertussis)
The Tdap vaccine is recommended during every pregnancy, regardless of the mother’s previous vaccination history. This is primarily to protect the newborn from pertussis (whooping cough), which can be life-threatening for infants too young to receive their first dose. The optimal timing for Tdap administration is between the 27th and 36th week of gestation.
Vaccinating during this window ensures the mother’s antibody levels peak approximately two weeks after the shot, maximizing the transfer of protective antibodies to the baby before birth. Infants whose mothers received the Tdap vaccine during the recommended period have a reduced risk of pertussis during their first two months of life. This protection lasts until the baby starts their own diphtheria, tetanus, and acellular pertussis (DTaP) series at two months of age.
Seasonal Influenza (Flu Shot)
The seasonal influenza vaccine can be administered at any time during pregnancy if the mother is pregnant during flu season. Pregnancy causes changes to the immune system, heart, and lungs, making a pregnant person more susceptible to severe complications from influenza. The flu shot uses an inactivated virus, making it safe for both the mother and the fetus.
Like the Tdap vaccine, the maternal flu shot generates antibodies passed to the baby, offering protection against influenza in the first months of life. This is important because young infants are at high risk for severe illness and hospitalization from the flu. The nasal spray flu vaccine, which contains a live-attenuated virus, is not recommended during pregnancy.
Vaccines That Should Be Avoided
While many vaccines are safe during pregnancy, live-attenuated vaccines are generally contraindicated due to a theoretical risk to the fetus. These vaccines contain a weakened, but living, form of the virus. Although there is no evidence they cause birth defects, they are avoided as a medical precaution against the possibility of the weakened virus replicating and causing a fetal infection.
The Measles, Mumps, and Rubella (MMR) vaccine is the most common example that should not be given during pregnancy. Rubella infection during early pregnancy poses a serious risk, including miscarriage, stillbirth, and congenital rubella syndrome. Immunity to rubella is important, but the vaccine must be given outside of the gestational period. The Varicella (chickenpox) vaccine is another live-attenuated immunization that is contraindicated for the same reason. Contracting chickenpox during pregnancy can lead to maternal complications, such as pneumonia, and result in congenital varicella syndrome for the baby if the infection occurs early in gestation. Women who are not immune to MMR or Varicella should complete vaccination before attempting to conceive.
Timing and Pre-Conception Planning
Timing is a significant factor in maternal immunization. Pre-conception planning provides an opportunity to ensure immunity against diseases that cannot be vaccinated against during pregnancy. A healthcare provider can perform a blood test to check for immunity to live virus diseases like rubella and varicella.
If a woman is non-immune to one of these live-attenuated diseases, the MMR or Varicella vaccine should be administered before pregnancy begins. After receiving a live vaccine, medical guidance recommends avoiding conception for at least 28 days. This waiting period ensures the vaccine virus is cleared from the mother’s system before pregnancy starts. Any vaccines missed or avoided during pregnancy, particularly the live-attenuated ones, should be prioritized immediately postpartum. Vaccines like MMR and Varicella are safe to receive while breastfeeding. Consulting with a healthcare provider is the best way to review vaccination history and create a safe, personalized schedule for pre-pregnancy and prenatal care.