Despite reassuring data, we can’t yet say U=U for breastfeeding

While effective HIV treatment greatly reduces the risk of onward transmission during breastfeeding, it does not appear that the risk is zero, a leading paediatrician told the British HIV Association (BHIVA) conference in London last week. Although formula feeding is the safest option in high-income countries, some women will choose to breastfeed and healthcare professionals should support them to do so as safely as possible.

Dr Hermione Lyall of St Mary's Hospital, London said that she and colleagues often needed to advise patients who were doing well on HIV treatment, with an undetectable viral load, who wished to breastfeed. Many are aware of World Health Organization (WHO) guidelines which recommend breastfeeding for women with HIV. Many women say that breastfeeding is expected by their families and that they also believe it is the right thing to do.

However, WHO guidelines are primarily written for countries with a high HIV prevalence where the lack of access to clean water means that the risk of HIV transmission through breastmilk must be weighed against the risks of infant malnutrition, infections and mortality posed by formula feeding. In contexts where these risks are not present, such as the UK, guidance recommends that mothers living with HIV stick to formula feeding.

But should the UK guidance change in the light of our increasing understanding of the impact on HIV treatment and undetectable viral load on the risk of transmission? Does the statement “undetectable = untransmittable” (U=U) apply to breastfeeding as well as to sexual transmission?

There are very few data from the UK. Every year, around 1200 babies are born to women living with HIV. Since 2012, just 40 mothers have reported that they have breastfed. All were undetectable and no transmissions have occurred.

Most studies have been conducted in African countries or in India. A recent meta-analysis pooled data from studies on women who were breastfeeding while taking HIV treatment. It found a postnatal transmission rate of 1.1% after six months. Not included in that review, data from 1220 mother-infant pairs in the PROMISE trial showed a postnatal transmission rate of 0.3% after six months and 0.6% after 12 months. This suggests that the transmission risk increases with a longer duration of breastfeeding, although mixed feeding after six months may also have contributed.

Moreover, those studies did not correlate mothers’ viral loads with transmissions – mothers whose HIV treatment was not fully effective probably contributed to the transmissions that were seen in those studies. A Tanzanian study reported at the recent European AIDS Conference (EACS) is therefore of interest. Among 177 infants who were exclusively breastfed by mothers living with HIV who began HIV treatment before delivery, there were two transmissions. One was from a mother with a high viral load and the other from a mother who had stopped taking HIV treatment.

In contrast, there were no transmissions from mothers with undetectable viral loads. This suggests that there is a very low risk of breastfeeding transmission when viral load is suppressed, but these are not enough data to say that U=U, Lyall said.

Lyall recommended taking a harm reduction approach with mothers who express a wish to breastfeed. People will make healthier choices if they have access to adequate support, empowerment, and education, she said. Women should be advised that formula feeding has a zero risk of HIV transmission and is the safest thing to do. Breastfeeding is an option, but women must understand that they are taking a risk, even if it is a very small risk.

Advice should take account of the risk factors for HIV transmission during breastfeeding. Women who wish to breastfeed should be highly adherent to HIV treatment, have a viral load below 50 copies/ml (ideally throughout the pregnancy), should minimise the duration of breastfeeding, should engage with their multidisciplinary team and should be willing to be followed up monthly.

The Children’s HIV Association (CHIVA) is collaborating with patient advocates to produce patient information which simplifies the complex information on this topic, takes into account women’s preferences and attempts to guide them to the safest approach. It will include three key safety points that women should remember while they breastfeed:

• No virus: Only breastfeed if your HIV is undetectable.
• Happy tums: Only breastfeed if both you and your baby are free from tummy problems.
• Healthy breasts for mums: Only breastfeed if your breasts and nipples are healthy with no signs of injury or infection.