What do medical sources say about MMR Vaccine during pregnancy?

1st Trimester: CDC and ACOG list MMR as contraindicated during pregnancy, and AAP says it is not recommended. MotherToBaby says it is not known whether the vaccine changes miscarriage risk, and outcomes after the first trimester have been less studied. A 2020 review found no vaccine-associated cases of congenital rubella syndrome in the cohorts it examined, but the studies could not rule out very rare outcomes. A 2023 report described findings consistent with congenital rubella syndrome after early-pregnancy MMR; the M-M-R II label says a reported case had an unknown manufacturer, so it does not establish that M-M-R II caused the condition. CDC says an accidental dose is not a reason to end a pregnancy, while UKHSA uses stronger reassurance language. Ask your provider about your situation. 2nd Trimester: CDC and ACOG list MMR as contraindicated in every trimester, and AAP says it is not recommended during pregnancy. MotherToBaby says second-trimester vaccination has not been well studied and miscarriage risk is not known. A 2020 review found no vaccine-associated cases of congenital rubella syndrome in the cohorts it examined, but the studies could not rule out very rare outcomes. A 2023 report described findings consistent with congenital rubella syndrome after early-pregnancy MMR; the label also reports a postmarketing case involving an unknown manufacturer and a strain genotype that includes one used in M-M-R II; the reports do not establish cause. CDC says an accidental dose is not a reason to end a pregnancy, while UKHSA uses stronger reassurance language. Ask your provider about your situation. 3rd Trimester: CDC and ACOG list MMR as contraindicated in every trimester, and AAP says it is not recommended during pregnancy. MotherToBaby says third-trimester vaccination has not been well studied and miscarriage risk is not known. A 2020 review found no vaccine-associated cases of congenital rubella syndrome in the cohorts it examined, but the studies could not rule out very rare outcomes. A 2023 report described findings consistent with congenital rubella syndrome after early-pregnancy MMR; the label also reports a postmarketing case involving an unknown manufacturer and a strain genotype that includes one used in M-M-R II; the reports do not establish cause. CDC says an accidental dose is not a reason to end a pregnancy, while UKHSA uses stronger reassurance language. Ask your provider about your situation.

What do medical sources say about MMR Vaccine while breastfeeding?

MotherToBaby and ACOG say MMR can be given after birth while breastfeeding, and LactMed says nursing is not a reason to withhold it. LactMed says rubella vaccine virus can appear in milk, but infection is usually mild or causes no symptoms; it reports no clear evidence that measles or mumps vaccine virus appears in milk. In a 2016 study of 169 mothers who completed follow-up after measles-rubella vaccination, RNA was found in milk from two mothers, and no infant had clinical illness linked to breastfeeding. A 1982 rubella-only study found temporary infant antibodies without illness; SMFM says the vaccine is not transmitted in milk, but the available studies do not test combined MMR. Ask your provider about your situation.

Where do sources disagree on MMR Vaccine in pregnancy or breastfeeding?

How to describe inadvertent MMR exposure during pregnancy CDC and the US product label maintain a pregnancy contraindication and describe a theoretical fetal concern. A 2023 report describes one infant with findings consistent with CRS after early-pregnancy MMR, and the label records a postmarketing CRS case with an unknown manufacturer. UKHSA says rubella-containing vaccine in or shortly before pregnancy has no known risk, reports no safety concerns, and says an inadvertent dose is not a reason to recommend ending a pregnancy. The bodies agree that MMR is not recommended during pregnancy and that an inadvertent dose is not a reason to end a pregnancy. Their wording differs in how strongly it describes the remaining uncertainty. The UKHSA MMR page's October 2026 update does not by itself show that the MMR-specific evidence was newly reviewed; the parent update log says the change added MMRV pregnancy guidance. Keep avoid in all trimesters. Say that a rare CRS-like case has been reported, that the available studies do not show an established causal pattern, and that CDC does not consider inadvertent vaccination a reason to end a pregnancy. Do not repeat the unverified 1,600-pregnancy count or imply that the reported case proves causation.

Back to search

MMR Vaccine

Everyday exposureVaccines

Also called · 6 names▾

measles vaccine, mumps vaccine, rubella vaccine, MMR shot, measles mumps rubella shot, three-in-one vaccine

Live vaccine

General information · effects depend on amount, timing, and how it is used. About these sources

Pregnancy

CDC's 2025 guidance says MMR is contraindicated during pregnancy, describes the fetal concern as theoretical, advises avoiding conception for 28 days after vaccination, and states that an inadvertent dose is not a reason to terminate pregnancy. The M-M-R II label, revised June 2026, retains the contraindication and describes a postmarketing CRS case after inadvertent vaccination; the vaccine manufacturer was unknown. In the 2011 Latin American rubella-vaccine campaign cohort, 2,894 susceptible pregnant women were followed. Among 1,980 live births, 70 infants had rubella IgM, but none had CRS features attributed to vaccination. The 2020 systematic review found no vaccine-associated CRS cases in its included cohorts, while noting limits in comparison data and possible asymptomatic infection of infants with vaccine virus. Bouthry et al. (2023) reported an infant with findings consistent with CRS after inadvertent early-pregnancy MMR; one case does not establish causation. A 2026 VAERS analysis included 35 MMR pregnancy reports and recorded no birth defects or deaths among vaccine-error pairs, but passive reports cannot estimate incidence or exclude rare outcomes. MotherToBaby states that at least 1,600 pregnancies were vaccinated shortly before or during pregnancy, but the count could not be traced to one named primary dataset in the page's citations and is not used as a risk estimate.

Breastfeeding

LactMed's May 15, 2026 record says no studies evaluated combined MMR during breastfeeding. It reports that rubella vaccine virus can appear in milk and usually does not infect the infant; if infection occurs, it is generally well tolerated. LactMed also reports no clear evidence of measles or mumps vaccine virus in milk. In Hisano et al. (2016), 169 mothers completed follow-up after postpartum measles-rubella vaccination; measles RNA was isolated from the milk of two mothers, and breastfeeding was not associated with clinical disease in any infant. In Losonsky et al. (1982), a rubella-only postpartum study found infectious virus or antigen in milk from 11 of 16 breastfeeding mothers; 25% of breastfed infants had transient seroconversion without clinical disease. These small studies involved measles-rubella or rubella-only vaccines, not direct testing of combined MMR. SMFM states that vaccine is not transmitted in breast milk, a broad statement that does not reflect the milk-marker findings in these studies. ACOG and UKHSA support postpartum vaccination while breastfeeding.

How to describe inadvertent MMR exposure during pregnancy

Source A says: CDC and the US product label maintain a pregnancy contraindication and describe a theoretical fetal concern. A 2023 report describes one infant with findings consistent with CRS after early-pregnancy MMR, and the label records a postmarketing CRS case with an unknown manufacturer. (CDC: Guidelines for Vaccinating Pregnant Women, DailyMed: M-M-R II prescribing information, Bouthry et al., Pediatrics 2023: Congenital Rubella Syndrome Following Rubella Vaccination During Pregnancy)
Source B says: UKHSA says rubella-containing vaccine in or shortly before pregnancy has no known risk, reports no safety concerns, and says an inadvertent dose is not a reason to recommend ending a pregnancy. (UKHSA: MMR vaccine advice for pregnant women, UKHSA: Green Book Rubella chapter)
Why they differ: The bodies agree that MMR is not recommended during pregnancy and that an inadvertent dose is not a reason to end a pregnancy. Their wording differs in how strongly it describes the remaining uncertainty. The UKHSA MMR page's October 2026 update does not by itself show that the MMR-specific evidence was newly reviewed; the parent update log says the change added MMRV pregnancy guidance.
Other sources: ACOG's 2026 schedule marks MMR contraindicated during pregnancy; AAP says it is not recommended during pregnancy; the 2020 review found no vaccine-associated CRS cases in the included cohorts but noted limitations; MotherToBaby says miscarriage risk is unknown and describes one CRS report. (ACOG: 2026 Maternal Immunization Schedule, AAP: Guidance on Managing Infants with Congenital Measles as Disease Outbreaks Rise, Mangtani et al., Vaccine 2020: Safety profile of rubella vaccine administered to pregnant women, MotherToBaby: Measles, Mumps, and Rubella (MMR) Vaccine)
What the evidence shows overall: Keep avoid in all trimesters. Say that a rare CRS-like case has been reported, that the available studies do not show an established causal pattern, and that CDC does not consider inadvertent vaccination a reason to end a pregnancy. Do not repeat the unverified 1,600-pregnancy count or imply that the reported case proves causation.

Whether MMR vaccine material can pass through breast milk

Source A says: LactMed reports rubella vaccine virus can appear in milk, and primary rubella or measles-rubella studies detected viral material in milk. The studies reported no clinical illness among infants in the cited cohorts, although transient seroconversion occurred in an older rubella-only study. (LactMed: Measles-Mumps-Rubella Vaccine, Hisano et al., Vaccine 2016: Evaluation of measles-rubella vaccination for mothers in early puerperal phase, Losonsky et al., Journal of Infectious Diseases 1982: Maternal-neonatal interactions after rubella immunization)
Source B says: SMFM states that the vaccine is not transmitted through breast milk and that breastfeeding does not interfere with immunity. (SMFM: Measles in Pregnancy Clinical and Patient Resources)
Why they differ: SMFM's broad wording does not distinguish the combined MMR vaccine from older rubella-only or measles-rubella studies, which found vaccine RNA, antigen, or virus in milk. The observed infant findings were usually absent or mild, and no study directly tested combined MMR during breastfeeding.
Other sources: MotherToBaby and ACOG allow postpartum MMR while breastfeeding; the M-M-R II label describes milk secretion and infant transmission of rubella vaccine virus, while LactMed says no combined-MMR breastfeeding study has been done. (MotherToBaby: Measles, Mumps, and Rubella (MMR) Vaccine, ACOG: 2026 Maternal Immunization Schedule, DailyMed: M-M-R II prescribing information, LactMed: Measles-Mumps-Rubella Vaccine)
What the evidence shows overall: Retain compatible while breastfeeding. Explain the difference between detecting vaccine material in milk and clinical illness in an infant. Do not repeat the categorical claim that no vaccine material can pass into milk.

How to confirm rubella or MMR immunity before pregnancy

Source A says: CDC's current patient page says to have a pre-pregnancy blood test to see whether a person is immune, and MotherToBaby says a provider can check antibodies when records are uncertain. (CDC: Vaccine Recommendations Before, During, and After Pregnancy, MotherToBaby: Measles, Mumps, and Rubella (MMR) Vaccine)
Source B says: The UK Green Book says routine antenatal antibody screening for rubella has stopped and directs clinicians to check MMR vaccination status and offer missing doses postpartum. (UKHSA: Green Book Rubella chapter)
Why they differ: The sources describe different national screening and documentation practices. This difference concerns how immunity is checked and when catch-up vaccination is offered, not whether MMR should be given during pregnancy.
Other sources: ACOG advises clinicians to assess measles immunity and notes that commercial IgG tests can miss prior immunity; CDC's technical guidance says routine pregnancy testing before MMR is not recommended. (ACOG: MMR Vaccination and Management of Obstetric-Gynecologic Patients During a Measles Outbreak, CDC: Guidelines for Vaccinating Pregnant Women)
What the evidence shows overall: Attribute the blood-test wording to CDC and the no-routine-antenatal-screening practice to UKHSA. Do not present one country's testing approach as universal.

Last reviewed 2026-10-14

Independent check 2026-10-14

Not yet clinician-reviewed

Ask your provider about your situation.

Varicella Vaccine
Flu Vaccine
Tdap Vaccine

MMR Vaccine

MMR Vaccine — Breastfeeding

What the research shows

What's in it / what was tested

Sources disagree

Options sources describe

Beyond pregnancy

All sources

Related