Babies of mothers infected by COVID-19 during pregnancy had three times the risk of respiratory distress compared with unexposed infants, even though the infants themselves were not infected with the virus, in a recent study. The risk of respiratory distress was significantly lower when the mothers were previously vaccinated. According to the researchers, even one mRNA vaccine dose prior to infection significantly reduced the odds that a full term infant would develop respiratory distress. Their report appears today in Nature Communications,
“We found unusually high rates of respiratory distress shortly after birth in the full-term babies born to mothers who had COVID-19 during pregnancy,” said senior author Karin Nielsen, professor of pediatrics in the division of pediatric infectious diseases at the David Geffen School of Medicine at UCLA. “The mothers had not been vaccinated prior to acquiring COVID, indicating that vaccination protects against this complication.”
The study also found that in-utero exposure to SARS-CoV-2 sparked an “inflammatory cascade” in the infants, increasing the risk of a breathing disorder.
SARS-CoV-2 infection during pregnancy has been associated with adverse maternal and neonatal outcomes, including increased risk of prematurity, stillbirths, and severe maternal morbidity and mortality. Estimates of vertical transmission of SARS-CoV-2 from mother to child are low, but there is growing concern about long-term health consequences for babies who were exposed in utero. Specifically, these authors write “Several authors have reported cases of infant respiratory distress (RD) among SARS-CoV-2-exposed uninfected (SEU) term neonates.”
The researchers used proteomics to determine that whip-like structures called motile cilia that help clear mucus from the respiratory tract did not function normally in the exposed infants stricken with respiratory distress. In addition, these infants had higher production of immunoglobulin E (IgE) antibodies.
Of the 221 mothers enrolled in the study, 151 (68%) were unvaccinated prior to infection, with severe or critical COVID disease present in 23 women (16%), compared with only three (4%) of vaccinated mothers.
The researchers found that 34 (17%) of 199 exposed infants followed in the study had respiratory distress, which is a very high frequency, as in the general, unexposed population respiratory distress happens in 5–6% of babies only. Twenty-one percent of babies with respiratory distress were born to mothers with severe or critical COVID-19, while only six percent of babies without respiratory distress were born to women with severe disease, a finding that was statistically significant.
Of the 34 infants with respiratory distress, only five (16%) were born to mothers vaccinated prior to infection, compared to 63 (41%) without the breathing disorder, indicating that vaccination had a protective effect.
“Not only do our results show higher rates of RD [respiratory distress] in SEU [SARS-CoV-2 exposed uninfected] infants when compared to the general population,” the researchers write, “but we observed more cases of RD at later gestational ages than anticipated, when neonates should presumably have more mature lung anatomy.”
