Topic Overview

Your immunity protects both you and your fetus. After you have been immunized (vaccinated) against or infected by a virus or bacteria, your body develops an immunity to that infectious agent. Full immunity can protect you from future infection, either for a lifetime or a limited period. Partial immunity strengthens your body's ability to fight that infection.

Before you become pregnant, be sure to review your immunization history with your health professional. To ensure a healthy pregnancy, make sure that you are immune to the following before conceiving:

Before pregnancy: Rubella, measles, mumps, chickenpox

Rubella, measles, mumps, and chickenpox can harm a growing fetus. They can cause birth defects, fetal death, or premature birth. Chickenpox can be dangerous for you when you're pregnant.

Whooping cough (pertussis) would be dangerous if your baby were to get it after birth. It is most serious in babies younger than 4 months of age and can be deadly.

If you don't know whether you're immune to rubella, measles, or chickenpox, talk to your health professional about a blood test for antibodies to that virus. If you aren't immune, have the vaccination before becoming pregnant. To allow time for your body to develop antibodies to the virus, keep using birth control for at least 4 weeks after the vaccination.

Your children should receive their immunizations on schedule. Having your child vaccinated against diseases does not increase your risk for becoming infected with them. You do not need to speed up or delay your child's immunizations.

Before or during pregnancy: Flu (influenza)

The flu can be dangerous for you when you're pregnant. If you will be pregnant during the October through mid-May flu season, get the seasonal flu vaccination before or during your pregnancy.footnote 2 This is especially important if you have a chronic illness or condition (including asthma). Also, get immunized against H1N1 flu. It's best to get the flu vaccine early, sometime in October or November, but you can get it any time during the season as long as the vaccine is available.footnote 1, footnote 2 The flu vaccine is effective for one season. When given during pregnancy, the flu vaccine injection is considered safe for your fetus and protects both you and your newborn.

If you are already pregnant and are not immune

If you are not immune to rubella, measles, or chickenpox, your health professional will recommend that you not have the vaccine until after childbirth. Instead, you must take every precaution to prevent exposure to these viruses while you're pregnant.

If you are not immune to hepatitis B, hepatitis A, rabies, polio, diphtheria, tetanus, whooping cough (pertussis), meningitis, or pneumococcal bacteria, you may be vaccinated during pregnancy. But your health professional is unlikely to recommend one or more of these vaccinations unless you are at risk of being exposed during your pregnancy.

Smallpox has been eliminated from all places in the world except for research labs. Smallpox vaccine is not recommended during pregnancy because of the small chance that it can affect you or the fetus. But risks related to the vaccine are not as great as the risk of having smallpox infection. So, in the unlikely event that you have or may have been exposed to smallpox, you would be vaccinated to reduce the severity of this life-threatening illness. For more information, see the topic Smallpox.

Routine vaccination is safe for you and your baby during breastfeeding.

For more information, see the topic Immunizations and topics related to the specific infections mentioned above.

Related Information



  1. National Advisory Committee on Immunization (NACI) (2009). Statement on influenza vaccination for the 2009–2010 season. Canada Communicable Disease Report, 35(ACS-6): 1–41. Also available online:
  2. American College of Obstetricians and Gynecologists (2010). Influenza vaccination during pregnancy. ACOG Committee Opinion No. 468. Obstetrics and Gynecology, 116(4): 1006–1007.


ByHealthwise Staff
Primary Medical Reviewer John Pope, MD - Pediatrics
Thomas M. Bailey, MD - Family Medicine
Specialist Medical Reviewer William Atkinson, MD, MPH -
Thomas Emmett Francoeur, MD, MDCM, CSPQ, FRCPC - Pediatrics

Current as ofFebruary 20, 2015