May 19: MIT Medical answers your COVID-19 questions. Got a question about COVID-19? Send it to us at CovidQ@mit.edu, and we’ll do our best to provide an answer.
If a pregnant woman tests positive for the virus, can the fetus be affected? Is she delivers, will the newborn be infected? And how about breastfeeding — could a baby be infected by breast milk from a mother who did not know she had the virus?
Because this is a new virus, there has not been a lot of research on these questions, but, says Medical Director and Obstetrician Cecilia Stuopis, studies done thus far have not found evidence of “vertical transmission” — the medical term for when a baby acquires an infection from its mother during pregnancy or childbirth. Two relatively small studies of COVID-19-infected mothers, involving nine and 38 subjects respectively, found that none of their babies were affected by the virus or tested positive. Two case studies (see here and here) reported that infants born to infected mothers had elevated levels of antibodies to the virus but no symptoms of illness.
However, vertical transmission cannot be ruled out completely in another study where three out of 33 infants born to infected mothers showed clinical signs of infection and tested positive. However, since the newborns in this study were not tested until three days of age, it’s possible that they were infected after birth.
“In any case, we think the chances of vertical transmission are extremely low,” Stuopis says. “However, we are concerned that a mom with COVID-19 could transmit the infection to her baby after delivery through respiratory secretions. So, most labor and delivery units are now routinely testing everyone upon admission. A mother who tests positive may be separated from her baby for some period of time after delivery and, once reunited, will be asked to practice excellent hand-washing and wear a mask to minimize the baby’s exposure to her secretions.”
There have been even fewer studies looking at the question of whether COVID-19 can be transmitted to babies through breast milk, but according to the CDC, available data suggest that this mode of transmission is unlikely. Dr. Stuopis concurs. While she notes that the CDC recommends precautions for breastfeeding mothers who are infected with COVID-19 — wearing a face covering, careful hand hygiene, and use of a dedicated breast pump if pumping — she stresses that the benefits of breastfeeding far outweigh any possible risk. “For most babies, breast milk can confer significant health benefits,” she notes, “including the transmission of beneficial antibodies, so we continue to recommend that mothers either breastfeed, or pump and feed the expressed milk to their baby.”