Press release
Tuesday, December 22, 2020
Pregnant women who are infected with SARS-CoV-2, the virus that causes COVID-19, in the third trimester are unlikely to transmit the infection to their newborns, suggests a study funded by the National Institutes of Health. The study looked at 127 pregnant women who were hospitalized in Boston in the spring of 2020. Of the 64 pregnant women who tested positive for SARS-CoV-2, none of the newborns tested positive for the virus. NIH support was provided by Eunice Kennedy Shriver The National Institute for Child Health and Human Development (NICHD), the National Institute of Heart, Lung and Blood (NHLBI) and the National Institute of Allergy and Infectious Diseases (NIAID).
“This study provides some assurance that SARS-CoV-2 infections during the third trimester are unlikely to pass through the placenta into the fetus, 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 led by Andrea G. Edlow, MD, M.Sc., of Massachusetts General Hospital and Harvard Medical School.
The researchers studied the occurrence of SARS-CoV-2 infection in the third trimester of pregnancy, assessing virus levels in respiratory, blood and placental tissue samples, the development of maternal antibodies, and how well these antibodies passed through the placenta to the fetus. indicator of potential immune protection from the mother) and examined the placental tissue. The reported results are limited to women in the third trimester, as data on infected women in the first and second trimesters are still collected and evaluated.
Of those who tested positive for SARS-CoV-2 in the study, 36% (23/64) were asymptomatic, 34% (22/64) had a mild illness, 11% (7/64) had a 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 tested positive for SARS-VOC-2 had detectable levels of the virus in their respiratory fluids, such as saliva, nasal and throat secretions, but no viruses in their blood or placenta.
The researchers found no significant differences between the levels of SARS-CoV-2 antibodies produced by pregnant and non-pregnant women. However, the study team observed lower-than-expected levels of protective antibodies in umbilical cord blood. Instead, they found high levels of flu-specific antibodies, probably from the mother’s flu vaccination, in umbilical cord blood samples from both 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.
The researchers believe that theirs is one of the first reports of less-than-expected transfer of SARS-CoV-2 antibodies to the fetus. Low transfer of these antibodies was observed, regardless of the woman’s severity of COVID-19 or whether she had an underlying health condition, 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 reduced antibody transfer makes newborns 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 may affect the health outcomes of premature babies, as COVID-19 may increase the risk of premature labor.
The study also found that the placentas in infected women were not different from those in uninfected women, although the risk of ischemia (reduced blood flow) in the placenta was higher for women with more severe COVID-19. According to a previous report, the researchers also found that while the placenta expresses major molecules used by SARS-CoV-2 to cause infections – the ACE2 receptor and the enzyme TMPRSS2 – the two molecules are rarely expressed together in the same location, which may help explain why the virus rarely affects the placenta.
The researchers suggest that their findings could help improve the care of COVID-19 pregnant women and their newborns, as well as provide information to help develop new vaccination strategies for pregnant women.
About Eunice Kennedy Shriver National Institute for 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 skills for all. For more information, visit https://www.nichd.nih.gov.
About the National Institutes of Health (NIH):
NIH, the national medical research agency, includes 27 institutes and centers and is a component of the US Department of Health and Human Services. NIH is the first federal agency to conduct and support basic, clinical, and translational medical research and investigate the causes, treatments, and cures of both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.
NIH … Transforming discovery into health®
Article
Edlow AG, et al. Assessment of maternal and neonatal SARS-CoV-2 viral pregnancy, transfer of transplacental antibodies and placental pathology during pregnancy during the COVID-19 pandemic. JAMA network open DOI: 10.1001 / jamanetworkopen.2020.30455 (2020)