Breastfeeding is generally encouraged, but specific circumstances exist where the risks of transmitting disease or harmful substances outweigh the benefits. A medical contraindication is a situation where a known condition, maternal treatment, or infant metabolic disorder poses an unacceptable risk to the baby’s health. These contraindications are rare, necessitating the use of formula or donor milk for infant safety. Any parent facing questions about continuing or stopping breastfeeding must consult immediately with a specialized healthcare provider for guidance based on current medical evidence.
Maternal Health Conditions That Prohibit Breastfeeding
Certain severe maternal infections risk transmitting the pathogen directly to the infant through breast milk. In the United States, Human Immunodeficiency Virus (HIV) infection is generally considered an absolute contraindication due to the risk of postnatal transmission of the virus. Although antiretroviral therapy (ART) significantly reduces this risk, US guidelines still generally recommend against breastfeeding to eliminate the small remaining risk. Mothers with HIV in the US are supported in using formula, while global guidelines in high-mortality settings may recommend breastfeeding with maternal ART, as the risk of infant death from other causes without breast milk can be higher than the risk of HIV transmission.
Human T-cell Lymphotropic Virus Type I or II (HTLV-I/II) is transmitted through human milk and is a definitive contraindication in most developed nations. This virus can lead to serious neurological diseases and certain types of leukemia. Mothers diagnosed with HTLV-I/II must avoid breastfeeding entirely.
Active, untreated Tuberculosis (TB) requires a temporary halt to direct breastfeeding, though this is managed differently than the viral infections. TB transmission occurs primarily through respiratory droplets and close contact, not through the milk itself. The mother must be temporarily separated from the infant until she has received at least two weeks of appropriate anti-tuberculosis treatment and is no longer contagious. During this period, the infant can safely be fed the mother’s expressed breast milk, and direct breastfeeding can resume once the mother is medically cleared.
Medications and Substances Requiring Formula Feeding
Powerful therapeutic drugs and illicit substances are contraindicated because they can pass into breast milk at toxic levels.
Cytotoxic chemotherapy agents, such as antimetabolites used in cancer treatment, are an absolute contraindication. They interfere with cell division and pose a severe risk of bone marrow suppression and immune compromise to the baby. These drugs require complete and permanent cessation of breastfeeding.
Radiopharmaceuticals, which are radioactive isotopes used in diagnostic or therapeutic procedures, necessitate a temporary but absolute cessation of breastfeeding. These substances transfer into the milk, exposing the infant to harmful radiation. The duration of cessation varies depending on the specific isotope and its half-life, requiring the mother to express and discard milk until the compound has cleared her system.
The use of illicit drugs, including cocaine and phencyclidine (PCP), is a clear contraindication due to acute toxic effects on the infant’s nervous system. These drugs pass into breast milk, causing irritability, tremors, and severe behavioral changes. Mothers in supervised, stable opioid maintenance programs (e.g., methadone or buprenorphine) may be supported to breastfeed if they have negative screenings for other illicit substances. However, substances like cocaine and PCP require formula feeding.
Infant Metabolic Conditions
The most definitive infant-related absolute contraindication to breastfeeding is classic galactosemia. This rare genetic metabolic disorder means the infant lacks the enzyme galactose 1-phosphate uridyltransferase (GALT), preventing the proper processing of galactose found in lactose. When the infant consumes breast milk, the unprocessed galactose and its metabolites build up to toxic levels, leading to severe complications including liver damage, cataracts, and intellectual disability. Infants diagnosed through newborn screening must immediately transition to a specialized, galactose-free formula for their entire lives. Classic galactosemia is the only inherited metabolic disorder that mandates the complete avoidance of human milk.
Temporary Contraindications and Special Scenarios
Some conditions require a temporary pause in direct feeding or a localized management plan rather than permanent cessation.
An active herpes simplex virus (HSV) infection is not a contraindication unless vesicular lesions are directly on the breast. If a lesion is present, direct feeding from that side must stop temporarily to prevent viral contact. The mother can safely continue to breastfeed from the unaffected breast and use expressed milk from the affected breast once the lesion is completely covered and healing.
Active maternal varicella (chickenpox) presents a specific risk if the rash onset occurs near delivery. If the mother develops symptoms from five days before to two days after birth, the infant needs temporary separation and passive immunization. During this highly contagious window, the infant can typically be fed the mother’s expressed milk.
In cases of severe maternal illness, such as septic shock or a major medical event, breastfeeding may be temporarily contraindicated because the mother is physically too ill to safely hold or nurse the infant. The focus is on stabilizing the mother’s health, and lactation support maintains the milk supply until direct feeding can safely resume. Expressed milk is often the bridging solution during these periods.