Misappropriated Human Milk: Fantasy, Fear, and Fact Regarding Infectious Risk

Barbara B. Warner, MD, FABFM; Amy Sapsford, RD, CSP, LD

Disclosures

NAINR. 2004;4(1) 

In This Article

The Infectious Risks

The advantages of using human milk have been well documented for term infants and include both nutritional and immunologic benefits.[7,8] Human milk use in a preterm population has additional benefits, including promoting gastrointestinal maturity and improving feeding tolerance. There are times, however, when infections in the mother could be transmitted to the infant through the human milk. What are the potential infectious agents that need to be considered when human milk misappropriation occurs?

The most significant concern on everyone's mind is the risk for HIV transmission. Since 1985 it has been clear that HIV can be transmitted through human milk.[9] Prospective studies done in Africa during the early 1990s demonstrated that long-term breastfeeding increases HIV transmission an additional 10 to 20% beyond transmission from pregnancy and delivery.[10,11] World Health Organization (WHO) estimates that HIV transmission through breastfeeding increases 2 to 10% when breastfeeding through two months of life and an additional 5 to 10% when breastfeeding through 24 months of life.[12] Factors that increased the likelihood of HIV transmission in a cumulative manner included the maternal viral load, volume of human milk ingested, duration of breastfeeding, inflammation or pathology of breast (ie, cracked nipples), presence of infant oral thrush, and introduction of formula to human milk feeding. The rate of transmission appears to be higher during the earlier weeks of breastfeeding, but continues to rise with increasing breastfeeding duration.[12] The Center for Disease Control and Prevention (CDC) summarizes these findings as follows: "The mechanism of HIV transmission through breastfeeding is most likely the frequent and prolonged exposure of infants oral and gastrointestinal tracts to human milk."[13] Given these findings WHO recommends that HIV-positive mothers in developed countries not provide human milk for their infants.

How then do these risks translate into a neonatal intensive care unit (NICU) setting? The following facts impact the potential for HIV transmission during a case of human milk misappropriation:

The occurrence of HIV among women of childbearing age in the United States is 0.2%.[14] This rate varies from 0.01% in more rural states, to as high as 0.8% in studies from urban medical clinics.[15] This number varies by geographic region and information on the site-specific incidence is important. No human milk from known HIV-positive women is ever stored within the NICU, as human milk feeding is contraindicated in this risk group in developed countries.[16]

Prenatal HIV testing is a recommended part of American College of Obstetrics and Gynecology (ACOG) screening panel. While testing remains voluntary, prenatal screening has helped to identify HIV-positive women before delivery and decrease the rate of perinatal infection.[16] As a result, the pool of undiagnosed HIV-positive mothers has decreased. Rates for prenatal HIV screening vary between geographic regions, and it will be important to be aware of screening patterns within individual regions.

The route of exposure is typically through a feeding tube or artificial nipple rather than at the breast. The duration of exposure is limited to one or a low number of feeds. This is in contrast to the 400 to 500 feedings that occur over the first months of life. The dose of exposure is limited to a small volume of overall feeds. There have been no reports in the medical literature of any cases of HIV transmission through misappropriated human milk feeding.

In summary, there is a very low likelihood that the human milk is contaminated, there is limited exposure, and the risk for transmission is low, even with known HIV-positive human milk. However, the true risk is unknown. Given the potentially serious effect, unknown true risk, and associated anxiety that is present, the following plan of care is recommended: In the case of misappropriated human milk feeding, obtain written consent to review the donor mother's prenatal labs (see Plan of Care). There should be no milk stored from HIV-positive mothers based on the WHO recommendation that human milk feeding is contraindicated for HIV-positive mothers in developed countries. If her HIV prenatal laboratory is negative, then no other evaluation is necessary. An exception to this would be mothers with a high-risk situation. The American Academy of Pediatrics (AAP) defines high-risk behavior as "injection drug users and sexual partners of known HIV-positive persons or active drug users."[17] If a high-risk situation is present, labs should be redrawn. If her HIV status is unknown then obtain consent and do HIV testing on the donor mother. Use the same test recommended by American College of Obstetricians and Gynecologists (ACOG) for prenatal testing, eg, Enzyme-Linked Immunosorbent Assay (ELISA) with Western Blot follow-up.

If the maternal HIV status is unknown, should HIV prophylaxis be started while awaiting the donor mother's laboratory results? Medications used in HIV prophylaxis have potentially serious side effects. The most common side effects include anemia, granulocytopenia, and feeding difficulties. Seizures, rashes, and hepatitis have also been reported. The risk associated with using these medications must be weighed against the risk associated with the risk of transmission from the misappropriated human milk. Given the low risk of transmission in a case of misappropriated human milk, HIV chemoprophylaxis is not routinely recommended. If a high-risk situation exists, as defined by the AAP and outlined above, then chemoprophylaxis should be considered. All options should be discussed with recipient infant's family.

Testing of the recipient mother is beneficial to verify that she is HIV negative, should the infant ever develop HIV. Given that the status of the recipient mother is more a legal than medical issue, testing of the recipient mother is optional at our site.

Experience within our unit has demonstrated that, as important as any test results, is education. Education should be provided to the staff, so they can speak clearly, consistently, and directly to the family. Rapidly providing accurate information with a clear plan of care has been most helpful to families in dealing with this stressful occurrence.

Infants born to hepatitis B surface antigen (HbsAg)-positive mothers are at increased risk of acquiring HBV infection and of developing chronic infections. The prevalence of positive HbsAg status among women of childbearing age is approximately 0.25%.[18] It is recommended that infants born to mothers that are HbsAg-positive receive both the immune globulin and HBV vaccine at birth to prevent perinatal transmission. These HbsAg-positive mothers can breastfeed. Particles of the HBV have been detected in human milk, but studies have not found breastfeeding to significantly increase the risk of infection in infants.[19] In the case of misappropriated human milk, the risk would again appear to be extremely low. The following plan of care is recommended for HBV in misappropriated human milk feeds:

Obtain written consent to review the donor mother's prenatal labs. If her prenatal HBsAg laboratory is negative, then no other evaluation is necessary. If there is a history of high-risk behavior in the donor mother then consider redrawing prenatal labs and administering hepatitis B immune globulin (HBIG) as well as HBV vaccine. If her HBsAg status is unknown, then obtain consent, do HBsAg testing, and administer the HBV vaccine if not yet received. The AAP already recommends that newborns receive the HBV vaccine at birth, which is very effective in preventing perinatal transmission. If her HBsAg status is positive, then give the HBV vaccine if not yet administered, and HBIG. While the risk for transmission is low, the side effects of HBV vaccine and HBIG are low as well. The recipient mothers HBsAg status should also be known as part of routine prenatal testing.

For HIV and HBsAg we have recommended the use of donor mothers' prenatal labs to evaluate risk status. New federal privacy rules emphasize the importance of obtaining permission to review prenatal labs. Consent forms therefore include consent for prenatal laboratory evaluation.

In the United States approximately 50% of women are seropostive for CMV by the time they reach reproductive age. Once having been infected, CMV may continue to be intermittently excreted in secretions throughout a lifetime, although no symptomatic disease is evident.[20] Transmission of CMV may therefore occur through human milk.[21] In term infants, although transmission may occur, risk of disease is low, presumably due to passively transferred antibodies. There is controversy regarding the risk of disease and long-term sequelae in preterm infants. Freezing of the human milk at -20°C will decrease viral titers, although it will not eliminate CMV completely.[22,23] Some experts advocate serologic screening of preterm mothers and for seropositive mothers to freeze their milk for three to five days.[24] Treatment of known perinatal or postnatal CMV is limited and not recommended routinely for even congenitally infected infants. Given the lack of information and controversy in preterm infants, the limited exposure with a misappropriated feed, and the lack of potential treatment and interventions we do not routinely recommend testing for CMV.

Hepatitis C particles have been identified in human milk from infected mothers. Transmission of HCV, however, has not been documented in the medical literature. United States Public Health Service guidelines currently do not list HCV as a contraindication to breastfeeding.[25] No testing is therefore recommended.

Culturing of expressed human milk will routinely identify a variety of bacterial species, including both Gram-positive and Gram-negative organisms, which do not pose a threat in the majority of cases. In preterm infants, bacterial infections from organisms transmitted through the human milk have been reported.[26,27] These include group B streptococcus, Staphylococcus aureus, and streptococcus species. There is no reliable way to determine whether bacteria found in human milk poses a risk. Neither culturing of the human milk nor treatment of the infant with antibiotics solely on the basis of misappropriated human milk would be recommended. Close monitoring of the infant for any signs and symptoms of sepsis, as is the routine in all NICUs, would be expected.

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