Immunizations in Pregnancy

Pregnancy is not only a time filled with wonder and joy, but also a time for women to optimize their health. It is important to focus on general healthy behaviors such as avoiding tobacco and excessive alcohol use, but during the flu season, generally fall and winter, it is also an excellent time to discuss immunizations in pregnancy. According to the American College of Obstetricians and Gynecologists (ACOG), immunizations are an essential part of prenatal care. Immunizations are known to reduce the risk and burden of infectious disease, not only to the mother, but also to the newborn child.

Both ACOG, and the CDC’s Advisory Committee on Immunization Practices (ACIP) recommend immunization against seasonal influenza to any woman who is pregnant during the flu season. Because hormonal changes in pregnancy can make pregnant women more prone to infections, influenza can be especially risky during pregnancy. Influenza infection during pregnancy can be more severe, and increases the risk of preterm and cesarean delivery.

For example, during the 2009 H1N1 pandemic, pregnant women accounted for five percent of all deaths, but made up only one percent of all influenza infections. Moreover, influenza infection in the first trimester increases the risk of congenital anomalies. Immunization reduces the risk of influenza illness, hospitalizations, and also protects the infant for several months after birth.

Tetanus, diphtheria, and acellular pertussis (Tdap) is another vaccination recommended by both ACOG and the ACIP. Vaccinating the mother transfers antibodies to the fetus that protect it during the newborn period against the respiratory illness pertussis, also called whooping cough. This infection can be particularly severe for newborns, as they are vulnerable to this infection but are not vaccinated against whooping cough until two months of age.

In fact, most children who are hospitalized for pertussis are those that are less than two months old— vaccination can reduce this risk by almost 50 percent.  Tdap is therefore recommended with every pregnancy (even if you have had the vaccination previously) around 28 weeks. This ensures that antibodies to pertussis are transferred from the mother to her fetus with each pregnancy, protecting the newborn from serious pertussis in the first months of life.

Most immunizations are safe to administer during pregnancy. Immunizations are either derived from inactivated viruses, or from live, but weakened virus. Some examples of vaccines derived from inactivated viruses include influenza and Tdap. Immunizations made from a weakened (also called a live-attenuated virus) are contraindicated in pregnancy. Some examples of live-attenuated vaccines include the measles, mumps and rubella (MMR) and varicella vaccines; these should not be given during pregnancy. Some vaccinations, such as the pneumococcal, or hepatitis B vaccine, are recommended for certain pregnant women (i.e. women with diabetes mellitus). Most vaccines can be administered to post-partum and breastfeeding women.

The recent COVID-19 pandemic has highlighted the role that public health interventions, including immunizations, play in protecting the health of populations. Pregnant women should adhere to strategies recommended by the CDC that mitigate community spread of COVID-19 including hand washing, wearing masks, and social distancing. The U.S Food and Drug Administration has granted emergency use authorization to three COVID-19 vaccines and more will likely seek approval. Though pregnant women were excluded from the clinical trials of these vaccines, the CDC notes that limited data from animal studies have not demonstrated safety concerns.

According to ACOG and the Society for Maternal Fetal Medicine (SMFM), symptomatic pregnant women with COVID-19 are at increased risk of severe illness and death compared to non-pregnant peers. Therefore given these risks, both ACOG and SMFM stress that COVID-19 vaccines should not be withheld from pregnant women, and that pregnant individuals should be free to make their own informed decisions regarding COVID-19 vaccination after discussion with their provider. Information about COVID-19 is rapidly evolving, and women are encouraged to seek further information from the sources listed below as it comes out.

Being up to date with recommended immunizations is an excellent way of optimizing pregnancy care. Most immunizations are safe in pregnancy, and both the CDC and ACOG recommend vaccination with influenza and Tdap with each pregnancy.

Juan A. Peña, MD, MPH, is a Maternal Fetal Medicine fellow at the Icahn School of Medicine at Mount Sinai and a member of the Blavatnik Family Women’s Health Research Institute. His research and background are in Obstetrics and Gynecology and Preventive Medicine.