No evidence of mother-to-baby transmission of coronavirus, new preliminary study

Getty Images/iStockphoto
Getty Images/iStockphoto 

There is currently no evidence that coronavirus, now known as COVID-19, can be passed to a baby while in the womb, according to a small study of pregnant women in Wuhan, China.

As part of the study published on Wednesday in The Lancetresearchers examined the medical records of nine pregnant women with a confirmed diagnosis of COVID-19 pneumonia, who were admitted to Zhongnan Hospital of Wuhan University, Wuhan, China, between Jan 20 to Jan 31, 2020. 

All women were in their third trimester and all underwent a caesarean section. Researchers also tested samples of amniotic fluid and cord blood and collected swabs from the newborn babies. Breast milk samples were also taken from six of nine of the mothers. 

While the symptoms of pregnant women with COVID-19 pneumonia were diverse, with the main being fever and cough, the researchers found no evidence for vertical transmission of the virus in late pregnancy. Vertical transmission, also known as perinatal transmission, refers to the passage of a disease-causing agent from mum to baby during the period immediately before and after birth. Transmission may occur across the placenta, in breast milk, or through direct contact during or after birth.

And while there were two reported cases of "fetal distress", all nine pregnancies resulted in live births.

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The researchers note that the findings are similar to those observed with severe acute respiratory syndrome (SARS)."Previous studies have already shown no evidence of perinatal SARS infection among infants born to mothers who developed SARS infection during pregnancy," they write.

Study co-author, Professor Huixia Yang said that while existing studies into the effects of COVID-19 apply to the general population, there is limited information about the virus in pregnant women. "This is important to study because pregnant women can be particularly susceptible to respiratory pathogens and severe pneumonia, because they are immunocompromised and because of pregnancy-related physiological changes which could leave them at higher risk of poor outcomes."

But while he noted that in their study no patients developed severe pneumonia or died of their infection, "we need to continue to study the virus to understand the effects in a larger group of pregnant women."

Professor Yang and his colleagues also caution that a number of questions remain unanswered, including the effect of COVID-19 infection on the fetus in the first or second trimester. In addition, whether vaginal delivery increases the risk of mother-to-child transmission, and whether uterine contraction could increase the possibility of the virus ascending also needs to be further investigated. Further research also needs to determine whether the virus could damage the placenta.

An accompanying commentary in The Lancet written by Jie Qiao, (who was not involved in the study), notes that while the number of women studied was only small, "under such emergent circumstances" the findings are valuable for preventive and clinical practice in China and around the world.

But while there is, as yet, no reliable evidence to support the possibility of mother-to-baby transmission, Dr Qiao highlights that thus far, two babies have been diagnosed with coronavirus. One infant was diagnosed 17 days after birth after close contact with two confirmed cases. The second was diagnosed 36 hours after birth. In this case, missing details have meant doctors cannot conclude whether or not intrauterine COVID-19 infection occurred. 

According to Dr Qiao, as pregnant women are more susceptible to COVID-19 infection than the general population, especially if they have chronic diseases or maternal complication, expectant mothers and newborn babies should be considered key "at-risk populations" when it comes to strategies focusing on prevention and management of coronavirus.

Current medical advice from National Health Commission of China notes that babies of pregnant women with suspected or confirmed COVID-19 infection should be isolated for at least 14 days after birth and should not be breastfed.

It comes as health authorities in Hubei announced an additional 242 deaths and 14,840 cases of the virus, as of Thursday morning, the largest single-day rise since the epidemic began and almost 10 times the number of cases confirmed the previous day. Currently, there are 15 confirmed cases in Australia. Six of the earlier cases have recovered while the others remain in a stable condition. 

Around the world, there have been around 60,390 confirmed cases of coronavirus and 1,370 reported deaths. The fatality rate is currently 2.3 per cent.