The widespread availability of potent combination anti-HIV therapy (commonly called ART or HAART) has greatly reduced deaths from AIDS-related infections in high-income countries such as Canada, Australia and the U.S. and regions such as Western Europe. The tremendous power of ART is such that young adults who become HIV positive today who initiate ART are expected to live for several decades, provided they have no other pre-existing health issues and are engaged in their care and treatment. Due to the enormous benefit of ART, more and more HIV-positive people are thinking of having families.
An essential part of preventing mother-to-child transmission is HIV testing for women who are thinking of having a baby or who are pregnant.
Although HIV can be transmitted from mother to child—this is called vertical transmission—the risk of transmission can be reduced to less than 1% with the following steps, which are commonly followed in Canada and similar countries:
- prenatal counselling and care
- taking ART during pregnancy so that viral load is as low as possible
- having intravenous AZT (zidovudine, Retrovir) during delivery of the baby and Caesarian section for delivery (when medically necessary)
- a short course of anti-HIV medicines for the baby after birth
- use of formula rather than breastfeeding (HIV can be transmitted via breastfeeding)
- not pre-chewing food for the baby when solids are introduced. Adults who have both HIV and oral infections can inadvertently cause a small amount of blood to leak and be present in the food that they chew. This blood can contain HIV, and if the pre-chewed food is fed to the infant, it could transmit HIV.
Without ART, the risk of vertical transmission can be at least 26%.
Focus on breast milk
Breast milk is the ideal source of nutrients for babies. Furthermore, breast milk contains substances that help the immune system fight diseases that affect the lungs, stomach and intestines. Such infections are relatively common in low-income countries. In these countries, illness and death rates among infants are high, and so breast milk plays an important role in supporting the health of infants.
As studies have found that breastfeeding helps babies in low-income countries survive, the World Health Organization (WHO) has revised its feeding guidelines for infants born to HIV-positive mothers in low- and middle-income countries. In such countries, infectious diseases (other than HIV) and malnutrition are the leading causes of death among infants. Moreover, clean water is not always available and baby formula is relatively expensive. Therefore, the WHO feeding guidelines for these countries recommend breastfeeding for infants born to HIV-positive mothers.
However, beast milk can also transmit HIV. The risk of transmission exists whether or not breastfeeding is done at an early or older age. The risk of HIV transmission via human milk can vary from 14% in mothers with chronic HIV infection to between 25% and 30% in mothers who become infected late in pregnancy.
HIV and ART in breast milk
Unfortunately, studies in Southern Africa have found that the use of ART by HIV-positive pregnant women and/or by infants born to HIV-positive mothers does not eliminate the risk of HIV transmission from breast milk. In such cases, transmission rates can vary between 1% and 5%. Moreover, HIV transmission can occur via breast milk even if the mother’s viral load in the blood is below the level that can be assessed by commonly used tests (that is, the result is “undetectable”).
It can take weeks or months of the mother taking daily ART to reduce viral load in her breast milk. Furthermore, different anti-HIV drugs have different abilities to penetrate human milk. Thus the concentration of some drugs will be higher in breast milk than in the mother’s blood while the concentration of other drugs will be lower in breast milk than in the blood.
Clinical trials of ART in HIV-positive mothers for the purpose of reducing mother-to-child transmission of HIV via breast milk have been done in low-income countries. According to researchers, although the toxicity of these drugs to the infants was low, some infants developed “severe anemia” and others had multidrug-resistant HIV infection.
Breastfeeding can cause nipples to become sore, chapped and inflamed, which can lead to infections of the breast, such as mastitis. Infections, with their accompanying inflammation, can increase the risk of HIV transmission via breast milk.
Furthermore, recent research in both the U.S. and southern Africa has found that adherence to HIV medicines by some mothers is less than ideal, particularly after giving birth. A reduced ability to take ART every day, exactly as directed, could give rise to drug-resistant HIV and raise levels of HIV in breast milk, increasing the risk of transmission.
The safest option
Based on these and other studies, the American Academy of Pediatrics (AAP) made the following statement:
“Therefore, in the U.S., where there is access to clean water and affordable replacement feeding, the AAP continues to recommend complete avoidance of breastfeeding as the best and safest infant feeding option for HIV-infected mothers, regardless of maternal viral load and antiretroviral therapy.”
Moreover, the AAP recommends that doctors counsel HIV-positive women to avoid breastfeeding and to document this in their medical records. The AAP adds: “If financial resources are identified as a barrier to avoiding breastfeeding, physicians should assist in identifying appropriate financial support to access infant formula.”
In Canada and other high-income countries, HIV-positive mothers are given subsidized access to infant formula.
Donated human milk
The AAP notes that, in general, some mothers use donated breast milk, particularly for infants who are sick or born prematurely and who are recovering in intensive care units (ICUs).
To reduce the potential for HIV transmission via donated human milk, the following steps need to be taken:
- appropriate selection and screening of donors
- careful collection, processing and storage of milk
The AAP states that “donor human milk banks that belong to the Human Milk Banking Association of North America voluntarily follow guidelines of the Centers for Disease Control and Prevention (CDC), which include screening of donors for infectious transmissible agents as well as heat treatment of the milk.”
Heating human milk at a temperature of 62.5 ˚C for at least 30 minutes (also known as Holder pasteurization) is the only way to inactivate HIV in human milk. This is the standard used in donor milk banks in the U.S.
Heating human milk in a water bath to 100˚C and removing it once the water reaches a rolling boil and then allowing it to cool before feeding has been recommended as a potential way of pasteurization in low-income countries. This process is called flash-heat pasteurization. Although it can destroy HIV circulating freely in human milk, flash-heating does not destroy HIV that is attached to or inside cells of the immune system that are found in human milk.
Therefore, the AAP warns that flash-heating of human milk is not recommended in the U.S. because clean water and subsidized baby formula are available to HIV-positive women.
The AAP encourages HIV-positive mothers to avoid what it refers to as “informal milk-sharing practices”—meeting potential milk donors over the Internet or by word of mouth. Milk obtained from such practices cannot be guaranteed to be safe for babies because donors have not been formally screened for infectious diseases.
Some parents pre-chew food for infants who are starting to eat solids. However, the CDC has investigated cases where HIV transmission occurred because an HIV-positive adult chewed food before feeding it to a child (this is called premastication). HIV transmission likely occurred because of cuts, sores or lesions in the mouth of the HIV-positive chewer. Specifically, because of oral infections in the adult, blood that contained HIV leaked into the food and was inadvertently passed on to the infant. Also, some infants can have oral infections, which may increase their risk of becoming infected with HIV if exposed to the virus.
Therefore, the AAP encourages doctors caring for HIV-positive women with infants to ask them about pre-chewing food, warn them about the risk of HIV transmission and discuss “safer feeding options” with them.
Protecting infants from HIV
The statement by the AAP provides useful advice for doctors, nurses and other healthcare providers to help minimize the risk of HIV transmission from mother to child. It is relatively short—containing 11 recommendations.
By adhering to the recommendations in the document, physicians and other healthcare providers in North America should be able assist HIV-positive mothers in giving birth to healthy babies and keeping those babies free from HIV.
—Sean R. Hosein
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