MMR and Breastfeeding
The rubella vaccine virus does pass through the breast milk of women who get the MMR vaccine (M-M-R II); there is some concern that rubella could be transmitted to a nursing infant this way. While many organizations consider it safe to receive MMR while breastfeeding, you should talk to your healthcare provider if you are thinking of getting this vaccine while nursing.
The MMR vaccine (officially known as M-M-R® II) is used to prevent measles, mumps, and rubella. Although the Centers for Disease Control (CDC) and several other notable organizations state that almost all vaccines -- including MMR -- do not affect the safety of breastfeeding, there is some concern that breastfeeding women who get the MMR vaccine might transmit the rubella virus to their infants.
Research has demonstrated that the rubella vaccine virus can pass through breast milk. Although this is unlikely to cause problems in most situations, there has been one reported case of infant rubella possibly caused by the breastfeeding mother getting the MMR vaccine.
You should talk with your healthcare provider about MMR and breastfeeding. Each woman's situation is different, and you and your healthcare provider understand your situation best. After considering what you want and expect, as well as your current health situation, the two of you can make a shared decision that is right for you.