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Three newborns out of 33 in Wuhan, China, tested positive for COVID-19 in what may be the first evidence of vertical transmission of the virus, researchers said.

"Because strict infection control and prevention procedures were implemented during the delivery, it is likely that the sources of SARS-CoV-2 in the neonates' upper respiratory tracts or anuses were maternal in origin," wrote Wenhao Zhou, MD, of Children's Hospital of Fudan University in Shanghai, China, and colleagues, writing in a

While the authors noted two recent studies found no clinical findings or investigations suggestive of COVID-19 and all samples were negative, "the vertical maternal-fetal transmission cannot be ruled out in the current cohort."

Christopher Golden, MD, of Johns Hopkins University in Baltimore, who was not involved with the research, told 番茄社区app he thought there was a "strong possibility" there was vertical transmission of COVID-19.

"They would need to match PCR results from mother to baby do an absolute confirmation" that it was not a healthcare worker with COVID-19 who may have infected the baby, he said. "That would be the slam dunk, that would be the definitive answer."

Zhou and colleagues said that so far, only 19 infants born to affected mothers have been studied in prior research and "no information on early-onset infection in newborns has been published in previous studies."

The researchers examined data on 33 neonates born to mothers with COVID-19. All three of the infants testing positive were boys; their tests were performed on days 2 and 4 of life via nasopharyngeal and anal swabs, and they had chest radiographs showing pneumonia. Two of three cases, born at around 40 weeks gestation via cesarean delivery, presented with lethargy and fever, though the second case also had vomiting. One had abnormal lab values, while the other's were normal.

The third case was born at 31 weeks via cesarean delivery due to fetal distress, and maternal COVID-19 pneumonia. This infant received non-invasive ventilation and caffeine, as well as antibiotics for suspected sepsis that improved after treatment.

Similar to previous studies, Zhou's group described the cases as "mild" and outcomes "favorable," with the most seriously ill neonate showing more illness from prematurity, asphyxia, and sepsis than from COVID-19. All three infants tested negative for the coronavirus by day 7.

Golden pointed out that two of the three babies in the current study had other reasons for respiratory distress: one aspirated meconium, and the preterm infant with Gram-negative bacteremia would also be highly susceptible.

"All three came back to baseline," which is "reassuring that disease may be mild in these babies," he said, though he noted this was a small sample, with data from only one hospital.

Zhou and colleagues noted that maternal samples of amniotic fluid, cord blood, and breast milk were negative for the virus. Nevertheless, they recommended screening pregnant women and instituting "strict infection control measures" when tests are positive, including quarantining infected mothers and closely monitoring their newborns.

A Growing Body of Evidence

Additional reports released on Thursday in JAMA provided , this time through antibody testing.

One report by Jing Yang, MD, of Renmin Hospital of Wuhan University, and colleagues, presented the case of an infant girl delivered by cesarean section to a mother with COVID-19 in a negative-pressure isolation room. Shortly after birth, tests showed the neonate had elevated antibody levels and abnormal cytokines.

"Although infection at delivery cannot be ruled out, IgM antibodies usually do not appear until 3 to 7 days after infection, and the elevated IgM in the neonate was evident in a blood sample drawn 2 hours after birth," the authors wrote.

They also noted lab results that found "inflammation and liver injury," which indirectly support the possibility of vertical transmission. As well, the mother's vaginal secretions were negative for SARS-CoV-2.

A second case series by Xinghua Long, MD, PhD, and Wei Zhang, MD, PhD, both of Zhongnan Hospital of Wuhan University, found that among six mothers with COVID-19, the virus was not detected via PCR testing in any of the newborns, but IgG concentrations were elevated in five infants, and elevated IgM concentrations were detected in two, though the authors noted IgM "is not usually transferred from mother to fetus because of its larger macromolecular structure."

However, they added IgM could have been produced "if the virus crossed the placenta."

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