The 2019 version of the coronavirus that has spread to about 50 countries across the world doesn't appear to be transmittable from pregnant mothers to newborns at birth. The new case study is the second out of China within the last month to confirm that mothers infected with coronavirus disease 2019 (COVID-19) during pregnancy did not infect their babies.

All four mothers in the current study gave birth at Wuhan's Union Hospital while infected. Wuhan in Hubei Province was the epicenter of the current outbreak that has sickened more than 100,000 people worldwide and killed more than 3,400, mostly in China. 

None of the infants developed any serious symptoms associated with COVID-19 such as fever or cough, though all were initially isolated in neonatal intensive care units and fed formula. Three of the four tested negative for the respiratory infection following a throat swab, while the fourth child's mother declined permission for the test. One newborn did experience a minor breathing issue that was quickly treated by non-invasive mechanical ventilation.

Two babies, including the one with a respiratory problem, did have body rashes that eventually disappeared on their own but there is no evidence these other medical issues and COVID-19 were related. All four infants remain healthy, and their mothers also fully recovered.

In a previous retrospective study on nine pregnant mothers infected with COVID-19, researchers also found no evidence that the viral infection can pass to the child. All nine births were done by cesarean section. Three of the four pregnancies in the current study were also brought to term by C-section.

In previous coronavirus outbreaks, scientists found no evidence of viral transmission from mother to child, but SARS and MERS were both associated with "critical maternal illness, spontaneous abortion, or even maternal death."

Coronavirus is in the same family as the cold rather than influenza but is much higher risk for people with preexisting conditions this year. Seasonal flu generally kills far fewer than 1 percent of those infected but COVID-19 is killing an estimated 3.4 percent. However, COVID-19 does not appear spread as easily as influenza.

The authors said further investigations into other aspects of potential COVID-19 infection in newborns and children are needed. For example, the sensitivity of the current diagnostic test for detecting the virus is about 71 percent, so they suggest evaluating its reliability in children. Toward that end, the researchers are collecting additional samples from the newborns, including placenta, amniotic fluid, neonatal blood and gastric fluid, among others, to detect possible receptors for the virus.