Can STDs Be Transmitted Through Breastfeeding? What Parents Need to Know

Several STDs can transmit through breastfeeding, but the picture is more nuanced than a simple yes or no. The infections that present genuine risk are HIV, HTLV-1, CMV in preterm infants, and active herpes lesions on the breast. For most other STDs — including chlamydia, gonorrhea, syphilis, and HPV — breastfeeding is safe with appropriate treatment.

Quick answer: HIV can transmit through breastmilk. Mothers with HIV in the US are advised not to breastfeed and to use formula. HTLV-1 (human T-lymphotropic virus) also transmits through breastmilk. Syphilis, chlamydia, and gonorrhea do not transmit through breastmilk but require prompt treatment to protect the infant from transmission during delivery. HPV does not transmit through breastmilk. Herpes does not transmit through breastmilk unless there is an active lesion on the breast or nipple. Testing and treatment resources: Los Angeles, Houston, New York City, Miami, Chicago.

HIV and Breastfeeding

HIV is present in breastmilk and can transmit from mother to infant. Without intervention, breastfeeding by an HIV-positive mother carries a 5–20% risk of transmission to the infant over the breastfeeding period. In resource-rich settings including the US, the recommendation is for HIV-positive mothers to formula-feed and avoid breastfeeding entirely.

In resource-limited settings where clean water and formula access are unreliable, WHO guidelines support breastfeeding with simultaneous maternal ART, which substantially reduces transmission risk. The context-specific guidance reflects that in some settings, the risks of formula feeding (diarrhoeal disease from unsafe water preparation) may exceed the risk of HIV transmission with ART-suppressed breastfeeding.

A mother with HIV on effective ART with an undetectable viral load has a much lower risk of transmission than untreated HIV, but US guidelines nonetheless recommend formula feeding as the safer choice where it is reliably accessible.

HTLV-1 and Breastfeeding

HTLV-1 (human T-lymphotropic virus type 1) transmits efficiently through breastmilk, with breastfeeding being the primary route of mother-to-child transmission. HTLV-1 causes adult T-cell leukaemia/lymphoma and HTLV-1-associated myelopathy in a subset of infected individuals, with long latency periods. HTLV-1 is endemic in Japan, the Caribbean, parts of Africa and Latin America, and among some indigenous Australian populations. Women known to be HTLV-1 positive should not breastfeed.

Herpes and Breastfeeding

HSV does not transmit through breastmilk itself. The risk is from direct contact with active herpes lesions. A mother with herpes can breastfeed safely as long as there are no active lesions on the breast or nipple. If there is an active outbreak on or near the breast, breastfeeding from that breast should be avoided (milk can be expressed and discarded); feeding from the unaffected breast is safe. Herpes on other body parts does not affect breastfeeding safety if covered and hands are washed before contact with the infant.

Syphilis, Chlamydia, Gonorrhea

These bacterial infections do not transmit through breastmilk. However, they can transmit to the infant during delivery (see How STDs Affect Pregnancy for detailed guidance). A mother diagnosed with any of these infections should be treated promptly. Treatment with appropriate antibiotics is safe during breastfeeding for all three infections.

HPV

HPV does not transmit through breastmilk. Breastfeeding is not contraindicated in women with HPV.

When to Seek Urgent Care

• HIV-positive and currently breastfeeding: consult your infectious disease or HIV clinician and paediatrician immediately about transitioning to formula and appropriate infant prophylaxis.

• Active herpes outbreak on the breast while breastfeeding: stop breastfeeding from that breast and contact your midwife or OB for guidance.

• Positive syphilis test while breastfeeding: start penicillin treatment same day; breastfeeding can continue.

Frequently Asked Questions

Can a baby get chlamydia from breastfeeding?

No. Chlamydia does not transmit through breastmilk. Neonatal chlamydia infection occurs during vaginal delivery, not through breastmilk. Treatment of the mother with azithromycin or amoxicillin during breastfeeding is safe.

If I have herpes, can I breastfeed?

Yes, with the precaution that you should not breastfeed if there is an active herpes lesion on the breast or nipple. Herpes anywhere else on the body does not contraindicate breastfeeding provided good hand hygiene is maintained. Valacyclovir and acyclovir are considered safe during breastfeeding.

Related: How STDs Affect Pregnancy · Understanding HIV · Herpes Myths · Get tested today →