After several months of the world believing that a pregnant woman cannot transmit novel coronavirus infection to her unborn baby, evidence has been emerging to suggest that this can indeed happen. Earlier this week, the Indian Council of Medical Research (ICMR) laid down the need for healthcare workers and obstetricians to factor in the consequences of the “probable” vertical transmission of COVID-19 (the disease caused by the novel coronavirus) and take precautions accordingly.
What is vertical transmission?
Vertical transmission refers to the transmission of an infection from a pregnant woman to her child. It can be antenatal (before birth), perinatal (weeks immediately prior to or after birth) or postnatal (after birth). This is of grave concern not just because it can potentially cause a newborn to be very sick, but also because the mechanism of how and when this happens is not always very clear. In a 2017 review article in the journal Cell Host Microbe, scientists from the University of Pittsburgh wrote: “Despite the devastating impact of microbial infections on the developing fetus, relatively little is known about how pathogens associated with congenital disease breach the placental barrier to transit vertically during human pregnancy.”
Among infections of which vertical transmission has been known to happen are HIV, Zika, rubella and the herpes virus. In fact, one of the biggest worries about the Zika outbreak a couple of years ago was the possibility of babies being born with birth defects.
What has ICMR said?
ICMR has issued a Guidance for Management of Pregnant Women in COVID-19 Pandemic. It says: “With regard to vertical transmission (transmission from mother to baby antenatally or intrapartum), emerging evidence now suggests that vertical transmission is probable, although the proportion of pregnancies affected and the significance to the neonate has yet to be determined.”
The guidelines deal with the protocol that health workers need to follow right from notification of cases, antenatal and postnatal care that needs to be given to the mother and baby, and the use of appropriate personal protective equipment, so that there is no transmission of the infection from the mother to health staff attending to her, especially during labour when chances are very high of the baby and the staff coming in contact with her body fluids.
It also follows international norms in recommending that the baby should be isolated after birth, highlighting the lack of enough scientific knowledge about the chances of a COVID-19-affected baby developing complications. “It is unknown whether new-borns with COVID-19 are at increased risk for severe complications. Transmission after birth via contact with infectious respiratory secretions is a concern. Facilities should consider temporarily separating (e.g. separate rooms) the mother who has confirmed COVID-19 or is a PUI (person under investigation), from her baby until the mother’s transmission-based precautions are discontinued,” says the ICMR document.
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Incidentally on April 3, days before this document came out, India’s first baby born to a COVID-19-positive woman had been delivered in AIIMS. He is COVID-19-negative. The baby’s father, who is a resident doctor in AIIMS, and his mother both had tested positive for the disease.
What is the available scientific evidence on vertical transmission?
The science of whether there is vertical transmission is evolving, much like the rest of our knowledge about the novel coronavirus (SARS-CoV2). On February 12, researchers from Wuhan University looked at nine pregnant women and came to the conclusion in an article in The Lancet: “The clinical characteristics of COVID-19 pneumonia in pregnant women were similar to those reported for non-pregnant adult patients who developed COVID-19 pneumonia. Findings from this small group of cases suggest that there is currently no evidence for intrauterine infection caused by vertical transmission in women who develop COVID-19 pneumonia in late pregnancy.”
Ten days later, something happened that changed the understanding of COVID-19 in the context of vertical transmission.
BORN POSITIVE: Another group of researchers from the same university reported in the Journal of the American Medical Association the case of a woman with COVID-19 who delivered a baby girl on February 22 at Renmin Hospital, Wuhan. The baby was found positive both for the virus and antibodies against it soon after birth. It was the presence of the latter that led researchers to believe that the infection happened in utero. “The elevated IgM antibody level suggests that the neonate was infected in utero. IgM antibodies are not transferred to the fetus via the placenta. The infant potentially could have been exposed for 23 days from the time of the mother’s diagnosis of COVID-19 to delivery. The laboratory results displaying inflammation and liver injury indirectly support the possibility of vertical transmission,” the researchers reported.
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There are other instances too. Last month a baby born to a COVID-19-positive mother at the North Middlesex hospital in Enfield, had tested positive immediately after birth. Though doctors there were uncertain whether the infection actually was a result of vertical transmission or whether the baby had caught it after birth from somewhere else, NHS now says: “As this is a very new virus we are just beginning to learn about it. There is no evidence to suggest an increased risk of miscarriage. With regard to vertical transmission (transmission from mother to baby) the evidence now suggest that transmission is probable, although there has only been a single case reported. The significance to the neonate is not yet known and we will continue to assess and monitor the situation for women and babies.”
US VIEW: The US Centers for Disease Control and Prevention though still does not subscribe to the vertical transmission school. It maintains: “Mother-to-child transmission of coronavirus during pregnancy is unlikely, but after birth a newborn is susceptible to person-to-person spread. A very small number of babies have tested positive for the virus shortly after birth. However, it is unknown if these babies got the virus before or after birth. The virus has not been detected in amniotic fluid, breastmilk, or other maternal samples.”