Vaccines given during pregnancy rely on transplacental antibody transfer, according to the National Institutes of Health. When a pregnant woman receives an inactivated or mRNA vaccine, antibodies cross the placenta into the baby’s bloodstream, giving the infant baseline protection until they’re old enough for their own shots.
For the first time, the American College of Obstetricians and Gynecologists has published its own independent vaccine schedule for pregnant patients, marking a break from federal guidance. The move follows changes from the Department of Health and Human Services and the Centers for Disease Control and Prevention, which recently walked back recommendations for COVID-19 and flu shots during pregnancy.
In response, ACOG joined 13 other major medical organizations, including groups representing pediatricians and family doctors, to issue guidance grounded in peer reviewed research, cutting through public confusion to give expectant parents a clear, evidence-based path forward.
The science behind maternal immunization
Maternal immunization uses a mother’s immune system to build protection for her unborn child. Newborns enter the world with underdeveloped immune systems and cannot produce their own antibodies for months, leaving them vulnerable to serious respiratory infections.
Four vaccines recommended during pregnancy
Influenza vaccine: ACOG recommends a flu shot during any trimester, ideally by the end of October to ensure protection before flu season peaks.
COVID-19 vaccine: Breaking from current CDC guidance, ACOG recommends routine COVID-19 vaccination for all pregnant, postpartum and breastfeeding individuals, given as early as possible.
Tdap vaccine: This shot protects against tetanus, diphtheria and whooping cough and is recommended every pregnancy, ideally between 27 and 36 weeks to maximize antibody transfer before delivery.
RSV vaccine: To protect infants from respiratory syncytial virus, ACOG recommends one dose between 32 and 36 weeks of pregnancy, given seasonally from September through January across most of the continental U.S.
Why safety concerns persist
It’s natural for expectant mothers to feel cautious about what enters their bodies during pregnancy. Concerns that a vaccine could affect fetal development are common, and shifting federal guidance combined with online misinformation has deepened public uncertainty.
Experts say any small risk from vaccination must be weighed against the real danger of infection during pregnancy. Pregnancy naturally strains the cardiovascular, respiratory and immune systems, both influenza and COVID-19 carry heightened risks of severe illness if contracted during this time.
Common side effects of maternal vaccines
Most side effects are mild, temporary and pose no risk to the baby. Symptoms typically appear within 24 to 48 hours as the body builds immunity. The most common reaction is soreness or mild swelling at the injection site. Some patients also experience headache, muscle aches, low grade fever or fatigue that resolves within days.
Vaccines to avoid during pregnancy
While inactivated, recombinant and mRNA vaccines are considered safe, live attenuated vaccines are not recommended during pregnancy because they contain weakened virus forms. These include the chickenpox, HPV and MMR vaccines, typically advised for after delivery instead.
ACOG’s expert panel has also clarified that thimerosal containing flu vaccines remain safe and shouldn’t be delayed if thimerosal-free versions aren’t available, despite differing federal guidance.
Best practices for a safe vaccine schedule
The strongest RSV protection for infants comes from the mother receiving the vaccine during pregnancy. If a mother skips the shot or was already vaccinated in a prior pregnancy, her baby can instead receive a monoclonal antibody injection shortly after birth for similar protection. Experts recommend asking an obstetrician or midwife to review immunization history at the first prenatal visit and build a personalized schedule.
What happens if a vaccine is declined
Patients retain full legal authority to decline any vaccine during pregnancy. Experts recommend an open conversation with a provider about specific concerns, and declining typically involves signing a medical refusal waiver. Without vaccination, doctors recommend leaning on other measures, including frequent hand washing, avoiding crowded indoor spaces during respiratory season and ensuring everyone around a newborn is fully vaccinated.
The bottom line
ACOG’s new 2026 Maternal Immunization Schedule diverges from CDC guidance by continuing to recommend routine influenza and COVID-19 vaccination for all pregnant patients, alongside the widely accepted Tdap and RSV vaccines. These shots transfer protective antibodies from mother to baby during an infant’s most fragile months. Skipping Tdap leaves a newborn without antibodies against whooping cough, raising the risk of severe illness if exposed before two months old. Tracking data from global health organizations shows no statistical link between Tdap and preterm labor. With guidance from an OB GYN, expectant parents can make informed decisions for their newborns.
