A study from the National Institute of Child Health and Human Development (Nichd) Eunice Kennedy Shriver, the National Heart, Lung, and Blood Institute (Nhlbi), and the National Institute of Allergy and Infectious Diseases (Niaid) found that it is “unlikely ”That pregnant women with Covid-19 during the third trimester transmit the infection to their newborns.
The study followed 127 pregnant women who were admitted to Boston hospitals in the spring of 2020. Research shows that among the 64 pregnant women who tested positive for Covid-19, none of their newborns tested positive for the virus. .
“This study provides some reassurance that third trimester SARS-CoV-2 infections are unlikely to pass through the placenta to the fetus, but more research is needed to confirm this finding,” explained the director of Nichd. , Diana W. Bianchi.
As explained, the researchers studied the occurrence of SARS-CoV-2 infection in the third trimester of pregnancy and evaluated virus levels in samples of respiratory, blood, and placental tissue; the development of maternal antibodies; how well those antibodies passed through the placenta to the fetus – an indicator of possible immune protection from the mother – and examined the placental tissue.
These 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 Covid-19 in the study, 36% (23/64) were asymptomatic, 34% (22/64) had mild disease, 11% (7/64) had moderate disease, 16 % (10/64) had serious illness and 3% (2/64) had critical illness. The study included, as comparators, 63 pregnant women whose test was negative and 11 women of reproductive age with Covid-19 who were not pregnant.
The team also found that pregnant women who tested positive had detectable levels of the virus in respiratory fluids such as saliva, nasal and throat secretions, but no viruses in the bloodstream or placenta.
Given this, the researchers found no significant differences between the levels of antibodies against SARS-CoV-2 produced by pregnant and non-pregnant women.
However, the study team observed lower levels of protective antibodies in the umbilical cord blood than expected. In contrast, they found high levels of influenza-specific antibodies, presumably from maternal influenza vaccination, in umbilical cord blood samples from women who tested positive and negative for SARS-CoV-2. The researchers suggest that these findings may indicate that antibodies to SARS-CoV-2 do not cross the placenta as easily as other maternal antibodies.
Low transfer of these antibodies was seen regardless of the severity of Covid-19 in the woman or whether she had an underlying health condition, such as obesity, high blood pressure, or diabetes.
The study researchers 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 Covid-19 compared to other infections.
They added that it will be important to determine how lower levels of maternal antibodies to coronavirus can affect the health outcomes of preterm babies because the virus can increase the risk of preterm labor.
It was noted that the placentas of infected women were also found to be no different from those of uninfected women, although the risk of ischemia – reduced blood flow – in the placenta appeared higher for women with more severe Covid-19.
Finalizing, they found that while the placenta expresses the main molecules used by SARS-CoV-2 to cause infection, the two molecules are rarely expressed together in the same location, which may help explain why the virus rarely affects to the placenta.
These findings are expected to help improve the care of pregnant women with coronavirus and their newborns, as well as provide information to aid in the development of new strategies to vaccinate pregnant women.
The National Institutes of Health (NIH) is the United States medical research agency, includes 27 institutes and centers, and is a component of the United States Department of Health and Human Services (HHS).