Press release
Tuesday, December 22, 2020
Pregnant women infected with SARS-CoV-2, the virus that causes COVID-19, during the third trimester are unlikely to transmit the infection to their newborns, a study funded by the National Institutes of Health suggests. The study followed 127 pregnant women who were admitted to Boston hospitals during the spring of 2020. Among the 64 pregnant women who tested positive for SARS-CoV-2, no baby tested positive for the virus. NIH support was provided by Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institute of Heart, Lung, and Blood (NHLBI) and National Institute of Allergy and Infectious Diseases (NIAID).
“This study provides some assurance that SARS-CoV-2 infections are likely to not pass through the placenta into the fetus during the third trimester, but more research is needed to confirm this finding,” said Diana W. Bianchi, MD , NICHD Director.
The study, published in the journal JAMA Network Open, was directed by Andrea G. Edlow, MD, M.Sc., of Massachusetts General Hospital and Harvard Medical School.
The researchers studied the onset of SARS-CoV-2 infection during the third trimester of pregnancy, assessing virus levels in respiratory, blood, and placental tissue samples, the development of maternal antibodies, the degree of passage of these antibodies by the placenta to the fetus an indicator of potential immune protection from the mother) and examined the placental tissue. The reported results are limited to women in the third trimester because data on infected women during the first and second trimesters are still being collected and evaluated.
Among those who tested positive for SARS-CoV-2 in the study, 36% (23/64) were asymptomatic, 34% (22/64) had mild disease, 11% (7/64) had moderate illness, 16% (10/64) had severe illness and 3% (2/64) had critical illness. The study included, as comparators, 63 pregnant women who tested negative for SARS-CoV-2 and 11 women of reproductive age with COVID-19 who were not pregnant.
The team found that pregnant women who were positive for SARS-VOC-2 had detectable levels of virus in respiratory fluids such as saliva, nasal secretions, and throat, but had no viruses in the bloodstream or placenta.
The researchers found no significant differences between SARS-CoV-2 antibody levels produced by pregnant and non-pregnant women. However, the study team observed lower-than-expected levels of protective antibodies in the umbilical cord blood. In contrast, they found high levels of influenza-specific antibodies, presumably from maternal influenza vaccination, in intimate cord blood samples from SARS-CoV-2 positive and negative women. The researchers suggest that these findings may indicate that SARS-CoV-2 antibodies do not pass through the placenta as easily as other maternal antibodies.
Researchers believe theirs is one of the first reports of the transfer of SARS-CoV-2 antibodies to the fetus less than expected. A low transfer of these antibodies was observed regardless of the severity of COVID-19 in the woman or whether she had an underlying health status, such as obesity, hypertension, or diabetes. The study authors noted that it will be important to determine why these maternal antibodies are less likely to cross the placenta and whether this reduction in antibody transfer makes infants more vulnerable to SARS-CoV-2 infection. , compared to other infections. The authors added that it will be important to determine how lower levels of maternal SARS-CoV-2 antibodies can affect the health outcomes of premature babies, as COVID-19 may increase the risk of preterm birth.
The study also found that the placentas of infected women were no different from uninfected women, although the risk of ischemia (reduced blood flow) to the placenta appeared to be higher in women with more severe COVID-19. In line with a previous report, the researchers also found that although the placenta expresses the major molecules used by SARS-CoV-2 to cause infection (the ACE2 receptor and the enzyme TMPRSS2), the two molecules rarely s ‘expressed together in the same place, can help explain why the virus rarely affects the placenta.
The researchers suggest that their findings could help improve the care of pregnant women with COVID-19 and their newborns, as well as provide information to aid in the development of new strategies for vaccinating pregnant women.
About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): NICHD conducts research and training to understand human development, improve reproductive health, improve the lives of children and adolescents, and optimize abilities for all. For more information, visit https://www.nichd.nih.gov.
Regarding the National Institutes of Health (NIH):
NIH, the country’s medical research agency, includes 27 institutes and centers and is a component of the U.S. Department of Health and Human Services. NIH is the leading federal agency that conducts and supports basic, clinical, and translational medical research, and investigates the causes, treatments, and cures for common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.
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Article
Edlow AG, et al. Assessment of maternal and neonatal SARS-CoV-2 viral load, transfer of transplacental antibodies, and placental pathology in pregnancies during the COVID-19 pandemic. JAMA network open DOI: 10.1001 / jamanetworkopen.2020.30455 (2020)