Spotlight Center on HIV Prevention Today


Pregnancy and Infant Feeding: Can We Say U=U About the Risk of Passing HIV to an Infant?

February 14, 2018

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Improvements in HIV treatment and prenatal HIV care have led to dramatic reductions in the transmission of HIV from a person with HIV to their baby (perinatal transmission). This has resulted in more people with HIV in Canada having children. The U=U (undetectable = untransmittable) campaign has contributed to increasing awareness that people who take HIV treatment and maintain an undetectable viral load are not at risk of passing HIV to their sex partners. As a result, some people are questioning whether this is also the case for perinatal transmission. Can an undetectable viral load eliminate the risk of passing HIV to an infant? This article will examine what we know about the risk of passing HIV through pregnancy, childbirth and infant feeding.

How Often Are Infants Born With HIV in Canada?

In Canada, as well as globally, we have seen dramatic decreases in the number of babies born with HIV, despite a growing number of babies born to women with HIV. Prior to the introduction of HIV treatment during pregnancy in 1994, the proportion of at-risk infants born with HIV in Canada was over 25%.1 This has dropped to 0.4% (one of 263 infants) in 2016.2 The only pregnancy that resulted in an infant with HIV in 2016 was from a woman with HIV who was not receiving any HIV treatment during pregnancy.

What Is the Risk of Transmission During Pregnancy and Delivery?

HIV transmission from a woman or trans person with HIV to their baby can take place during pregnancy, childbirth and after birth through infant feeding. For this reason, preventing perinatal transmission is more complicated than sexual transmission and requires multiple interventions directed at pregnant people and their infants.

Without treatment, between 15% and 30% of infants born to HIV-positive people acquire HIV during pregnancy or delivery.3 However, research shows that taking HIV treatment is the most effective way to reduce transmission to the baby.3-10 This is because successful HIV treatment lowers the viral load (a measure of the amount of HIV in the body) to undetectable levels. Having an undetectable viral load is good for the health of the pregnant person and it also reduces the risk of passing HIV to an infant. In fact, if a pregnant person is engaged in care, on HIV treatment and maintains an undetectable viral load throughout their entire pregnancy, studies have shown that the chance of passing HIV to their newborn is zero.7 In these studies, the newborn child also received a short course of HIV medication to help prevent transmission.

Related: No Transmissions From Breastfeeding in Tanzania Cohort From Mothers With Undetectable Viral Load


One of the major studies that showed the impact of treatment on preventing HIV transmission to a newborn was a French cohort study conducted between 2000 and 2011.7 This study found that no transmissions occurred among 2,651 infants born to women who were on treatment before they conceived and throughout their pregnancy, and who had an undetectable viral load at delivery.7 However, if treatment is not taken for the entire duration of pregnancy or if an undetectable viral load is not maintained, there is a risk of HIV transmission to the infant during pregnancy and/or delivery.7

HIV testing for pregnant people is important for finding those who are at risk of passing HIV to their infant. People who are diagnosed with HIV during pregnancy, or who are not adherent to treatment throughout pregnancy may have a higher risk of transmission to their infant, especially if they have a high viral load.3,11,12 When the risk of transmission may be higher due to an elevated viral load, a Caesarean delivery may be recommended to help prevent HIV transmission during childbirth since this is when the majority of perinatal transmissions occur if the viral load is detectable.13

Life-long HIV treatment is now recommended for all people diagnosed with HIV,14 and people with HIV who wish to become pregnant should consult with an HIV specialist as soon as possible, preferably before conception, to determine a suitable treatment regimen.13

What Is the Risk of Transmission Through Infant Feeding?

There are two possible routes of HIV transmission to an infant after birth – through breastfeeding (sometimes called chestfeeding for trans people), and through feeding an infant food that has been pre-chewed by a parent or caregiver who has HIV (this is also called premastication).


A systematic review of HIV transmission in breastfed infants of women on treatment found that the risk of transmission after birth was 1% after six months of breastfeeding, rising to almost 3% after one year.15 However, within these studies, the women were on treatment for varying amounts of time and did not continue treatment beyond six months after giving birth. The systematic review did not account for adherence nor viral load, which means we don’t know how many of the women had a detectable viral load at the time of transmission, despite taking HIV treatment.

There is very limited research on people on treatment who are breastfeeding that includes data on their viral loads. While an undetectable viral load does provide significant protection from HIV transmission, there have been cases of HIV transmission among breastfeeding women who had undetectable viral loads.16,17

A recent study from Tanzania reported no transmissions from breastfeeding women who had an undetectable viral load.18 In this study there were two HIV transmissions among 177 infants who were breastfed by women who started treatment before the infant was born, but in both cases the women had detectable viral loads.18

Some people breastfeed while also supplementing their infant’s diet with formula or other foods and liquids (known as mixed feeding). When done within the first six months of life there is a potential increased risk of HIV transmission to the infant compared to breastfeeding alone. Experts believe that this type of feeding can irritate and cause damage to the infant’s developing gut, allowing HIV to be passed more easily.19 However, in the context of being on treatment and having an undetectable viral load, mixed feeding is unlikely to increase the risk of HIV transmission.20

Pre-Chewing Food

Feeding an infant food that has been pre-chewed has been reported as a possible route of HIV transmission in three cases from the U.S.21 In all three suspected cases, young children acquired HIV after being born HIV negative, and none were breastfed. All three were fed food that had been pre-chewed by a parent or caregiver with HIV, whose HIV treatment status and viral loads were not reported. In two cases oral bleeding was reportedly present, which may have increased the risk of transmission.

We don’t know how often parents in Canada pre-chew their infant’s food but a study in the U.S. found that 31% of primary caregivers at nine pediatric clinics cared for children who received pre-chewed food.22 Of the 48 caregivers who reported pre-chewing food in this report, 79% were biological mothers with HIV.

To eliminate the risk of postnatal HIV transmission, parents with HIV in Canada are currently advised not to breastfeed (but rather to use formula exclusively) and not to feed their infants pre-chewed food. There are many programs across Canada that provide free formula for babies of people with HIV.

But Isn’t Breastfeeding Good for Babies?

Breast milk is good for infants because it provides nutrition and hydration, helps the baby’s immune system develop and helps fight off viruses and bacteria.23 In fact, the natural protection provided by breast milk is part of the reason why the majority of infants who are exposed to HIV through breastfeeding do not get HIV.23 However, formula is a feeding option that also provides the nutrition babies need to grow up healthy and strong.

The messaging around breastfeeding for people with HIV can be confusing. For people who do not have HIV, Health Canada recommends that newborn infants be breastfed exclusively for six months, continuing up to 24 months or more, with appropriate complementary feeding.24 This is similar to the World Health Organization (WHO) guideline on infant feeding and HIV, which recommends that women with HIV should breastfeed exclusively for the first six months, continuing for at least 12 months, while on treatment and receiving adherence support.20

However, the WHO guideline is intended for low-income countries where undernutrition and diarrheal diseases are common causes of infant mortality, and clean water to prepare formula is not always available. In these settings, feeding a baby formula may put them at increased risk of undernutrition, illness or death. In Canada and the U.S., where undernutrition and diarrheal diseases are not common, breastfeeding is not currently recommended for people with HIV because of the unknown risk of HIV transmission to the infant; while it is a low risk, it is likely not negligible.

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No Transmissions From Breastfeeding in Tanzania Cohort From Mothers With Undetectable Viral Load
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This article was provided by Canadian AIDS Treatment Information Exchange. It is a part of the publication Prevention in Focus: Spotlight on Programming and Research. Visit CATIE's Web site to find out more about their activities, publications and services.

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