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Infectious Diseases

Updated 28 August 2020

Breastfeeding unlikely to pass Covid-19 to babies, researchers say

Mothers should continue to breastfeed their babies, even if they have contracted Covid-19, as the benefits outweigh the risks, researchers suggest.

  • A new study found that breast milk is unlikely to be a source of Covid-19 infection for infants
  • The researchers tested over 60 samples of breast milk for SARS-CoV-2 RNA
  • Based on their findings, the team suggests that mothers continue to breastfeed their babies

The ever-evolving nature of the Covid-19 pandemic has opened a Pandora's box of anxiety for new mothers over whether they are capable of transmitting the new coronavirus to their infants through breastfeeding.

After analysing 64 samples of breast milk infected with SARS-CoV-2, the virus that causes Covid-19 disease, researchers from the University of California San Diego School of Medicine and University of California Los Angeles found that transmission is unlikely to happen.

The study was published in the online edition of JAMA.

Breast milk unlikely to be source of infection

Although there have been no documented cases to date of Covid-19 transmission from breast milk, researchers have been investigating the potential for this to happen.

For this specific study, the researchers examined 64 samples of breast milk from 18 women across the US infected with SARS-CoV-2. The samples were collected by the Mommy's Milk Human Milk Research Biorepository, an initiative involved in clinical research into human milk.

The authors wrote that one sample tested positive for viral RNA (coronaviruses are part of a large family of RNA viruses), but subsequent tests found that the virus was unable to replicate in breast milk, and therefore unable to cause infection in the breast-fed infant.

"Detection of viral RNA does not equate to infection. It has to grow and multiply in order to be infectious and we did not find that in any of our samples," said Christina Chambers, co-principal investigator of the study, and professor of paediatrics at UC San Diego School of Medicine.

"Our findings suggest breast milk itself is not likely a source of infection for the infant."

WHO guidelines recommend continuation of breastfeeding

A scientific brief published in June by the World Health Organization (WHO) recommends that mothers with suspected or confirmed Covid-19 should breastfeed their infants, and adds that the benefits of breastfeeding substantially outweigh the potential risks for transmission.

“[In] exclusively breast-fed infants, the risk of mortality is 14-fold higher in infants who are not breastfed,” the brief reads.

The benefits of early breastfeeding are significant, and according to a Health24 article, it is nutritionally complete, in that it can never be under or over-diluted; has psychological advantages; and leads to a reduced risk of babies developing infections.

There is also growing evidence that breastfeeding has short- and long-term health benefits for mothers, including lower risks for breast and ovarian cancer, cardiovascular disease and type 2 diabetes.

Professor Grace Aldrovandi, co-principal investigator of the study and chief of the Division of Infectious Diseases at UCLA Mattel Children's Hospital, also commented that in the absence of data, some women infected with SARS-CoV-2 have chosen not to breastfeed at all.

"We hope our results and future studies will give women the reassurance needed for them to breastfeed. Human milk provides invaluable benefits to mom and baby," said Aldrovandi.

Pasteurisation of milk safer for consumption

Part of the recent study involved the researchers mimicking conditions of the Holder pasteurisation process, a technique used to pasteurise milk in Canadian milk banks at 62.5 degrees Celsius for 30 minutes. This was done by adding SARS-CoV-2 to breast milk samples from two different donors who were not infected.

The samples were heated to 62.5 degrees C for 30 minutes and then cooled to 4 degrees C. Following pasteurisation, no infectious virus was detected in either sample.

"This is a very positive finding for donor milk, which so many infants, especially those born premature, rely on," said Chambers about the findings, while also acknowledging the importance of additional future studies with larger sample sizes to confirm these findings.

Another study published in the Canadian Medical Association Journal this month indicated that pasteurising the breast milk using the Holder method makes it safer for consumption. For this study, the researchers spiked human breast milk with a viral load of SARS-CoV-2 and tested samples that sat at room temperature and that were warmed up.

When they measured the samples for active virus, they found that the virus was inactivated in the pasteurised milk. 

Future work will also look at whether the breast milk contains active antiviral components, said Chambers, such as whether the antibodies to SARS-CoV-2 that women may produce after exposure to the virus can transfer to their infants through breast milk, and protect them from Covid-19.

READ | Benefits of breastfeeding

READ | Breastfeeding? Here’s what you should know

READ | Breast milk may help shield infants from dangerous viruses

Image: Getty/Jamie Grill