Detection of SARS-CoV-2 in Breastmilk
The biggest fear of breastfeeding newborns during the COVID-19 period is the fear of transmitting the virus through breastmilk. There is still not a substantiate amount of evidence available regarding the transmission of SARS-CoV-2 in breastmilk. Much of our knowledge comes from the data obtained from smaller studies and case reports (Table 1) [6,7,8,9,10,11,12,13,14,15,16,17]. To date, there have been no large-scale cohort studies or case-control studies evaluating the transmission of COVID-19 through breastmilk.
Furthermore, the scientific brief on breastfeeding and COVID-19 published by WHO on June 23, 2020, included a living systemic review performed by Centeno-Tablante et al., which showed that out of 46 COVID-19 positive mothers whose breastmilk samples were tested for SARS-CoV-2, 43 breastmilk samples tested negative, and only three samples tested positive. Out of the three mothers whose breastmilk samples were positive, only one infant tested positive for the virus, but the route of infection (breastmilk or close contact) could not be determined [18••, 19]. In another systemic review by Elshafeey et al., all 26 breastmilk samples from 26 mothers were negative for COVID-19 . A rapid systemic review of eight studies by Martins-Filho PR et al. showed that breastmilk samples of 24 pregnant women diagnosed with SARS-CoV-2 by PCR test were negative for the virus .
However, in addition to being smaller studies, there are several limitations associated with these reported studies. In most of the studies where the virus was detected in breastmilk, no precise information was available on sample collecting techniques. Also, only few of these studies tested breastmilk samples for the virus for several consecutive days. Groß R et al. reported that the breastmilk samples from one of the mothers in the study tested positive for four consecutive days before it tested negative [7•]. Chambers et al. reported that one out of 64 breastmilk samples was positive for the virus, but the same sample had tested negative 2 days prior as well as 12 and 41 days later . Tam et al. also reported the virus’s detection in the breast milk samples of a woman on day 1 and day 10 with five negative samples in between . But other studies did not perform such analysis of breastmilk samples for successive days. It means that even if the virus is excreted through the breastmilk, there is no clear data on the duration (in days) that the virus can be found in breastmilk. Besides, when the newborns test positive for COVID-19 and whose mothers are positive at the time of birth, it becomes challenging to establish whether the source or route of transmission is through breastmilk, through droplet transmission through close contact, transplacental, or even through the passage of the newborn through the birth canal. Hence, it becomes imperative to conduct more studies to look for possible transmission of the virus through breastmilk.
Detection of Viral Antibodies in Breastmilk
It is well-known that breastmilk protects the infant by providing antibodies during the first few months of life while the infant’s immune system is still developing. Whether the same is true in the case of COVID-19 is still not entirely known. There have been few reports suggesting the presence of IgG and IgA (immunoglobulins G and A) antibodies in breastmilk, which could offer immunity to the newborn from COVID-19 [22, 23]. Another preprint article revealed that the secretory IgA was present in 12 of 15 breastmilk samples from COVID-19 positive mothers . Even though this data is encouraging, detailed studies evaluating the protective effect of these antibodies against COVID-19 are warranted.
Recommendations for Breastfeeding for COVID-19 Mothers
During the earlier months of COVID-19, there appeared to be a lack of consensus regarding breastfeeding for COVID-19 positive mothers. In February 2020, Chinese experts recommended against breastfeeding for mothers with suspected or confirmed COVID-19. They advised initiating breastfeeding only if the mother and her breast milk samples tested negative .
Based on the currently available evidence, WHO has recommended that the mothers with confirmed or suspected COVID-19 should continue to breastfeed since the benefits of breastfeeding to both the mothers and newborns significantly outweigh the risk of transmission of COVID-19 to the newborns . These guidelines echo with the ones from the Centers for Disease Control and Prevention (CDC) and the Royal College of Obstetricians and Gynecologists. The mother should be willing to follow all necessary preventive measures to avoid the spread of infection to the newborn since infection can still pass from the mother to the baby through droplets. When the mothers must stay separated from the newborn due to their clinical condition or those mothers who are not comfortable following the preventive measures or who do not feel safe to breastfeed their newborns directly, the option of expressed breastmilk should be recommended (Table 2) . There is no clear evidence currently to support measures such as cleaning the breast before breastfeeding or disinfecting bottles or bags (accessories for collecting milk) before use as ways to decrease transmission of the virus .