How long after the MMR vaccine can you get pregnant?

What does the evidence say about MMR vaccine during pregnancy?

1. The CDC suggests waiting to get pregnant, if possible, until one month after receiving the MMR vaccine and confirming immunity with a blood test, since MMR is a live-attenuated vaccine with a very small theoretical chance of illness from the weakened viruses it contains. 1
2. Information from at least 1,600 pregnancies in which the MMR vaccine was given right before or during pregnancy found no increased chance of birth defects, though it is not known whether the vaccine raises the chance of miscarriage, and one documented case of congenital rubella syndrome followed a first-trimester vaccination. 2
3. A systematic review of 15 controlled studies on live vaccines given shortly before or during pregnancy found no significant increase in miscarriage, stillbirth, or birth defects overall, and estimated the likelihood of congenital rubella syndrome specifically at fewer than 1 per 1,000 exposed pregnancies, while noting the underlying evidence is very low quality. 3
4. Standard clinical guidance counsels patients to avoid becoming pregnant for 28 days after receiving MMR, and no reported cases of congenital rubella syndrome have occurred in women who received the rubella vaccine while already pregnant. 4
5. The reason immunity is worth confirming before conceiving: actual rubella infection during the first trimester carries a vertical transmission rate estimated up to 90%, and congenital rubella syndrome can include congenital cataracts, heart defects such as patent ductus arteriosus, and sensorineural hearing loss, with no specific antiviral therapy available once infection occurs. 5

Is MMR vaccine safe in each trimester?

• First trimester. Preconception planning. This is when a rubella immunity titer gets checked. If you're not immune, this is the time to get the MMR vaccine, before you're actively trying, so the waiting window doesn't compete with your cycle.
• Second trimester. Actively trying, inside the wait window. The standard advice is about one month between the shot and conceiving, using contraception in the meantime. This is a short, defined window, not an open-ended pause on trying to conceive.
• Third trimester. If pregnancy happens sooner than planned, during or right after vaccination. Aggregate data on this exact scenario is reassuring, but it is also the point to call your provider and get it on your chart, rather than manage it on your own.