The development of SARS-CoV-2 infection in the third trimester of pregnancy did not significantly affect the cellular and humoral immunity of the fetus, according to a study published in the Journal of Allergy and Clinical Immunology.
“Although there is no evidence of mother-to-child vertical transmission of SARS-CoV-2, it is urgent to clarify whether the maternal inflammatory response in the third trimester affects the development and physiological state of newborns,” reported the study authors.
The researchers studied a total of 71 infants born to mothers with clinically confirmed COVID-19 who were admitted to the neonatal intensive care unit (NICU) isolation ward of Zhongnan Hospital in Wuhan, China. After exclusion criteria, a total of 51 cases were eligible for further analysis.
All of the pregnant women underwent chest imaging before delivery. All chest imaging showed signs of changes corresponding to viral pneumonia. Among the women, 48 had a cesarean section. Following birth, newborns were isolated from mothers and placed in an incubator for observation. Apgar scores at 1 and 5 minutes were recorded and the first pharyngeal swab was collected 30 minutes after.
Blood samples were collected within 3 days after birth to detect immunoglobulin levels, cytokine concentrations, and lymphocyte subsets. RT-PCR testing was carried out to detect SARS-CoV-2. None of the newborns required mechanical ventilation during hospitalization, and “only a few” received low-flow nasal catheter oxygen for <3 days. All infants were fed formula and none received antiviral treatment. After 3 consecutive negative nucleic acid tests, the infants were sent home.
Among the mothers, the average age was 31 years. A total of 7 cases were positive for SARS-CoV-2 nucleic acid of which 4 cases presented with fever and cough; the remaining cases were asymptomatic. For the disease course, 10 cases (19.6%) had begun within 1 week of delivery, 14 cases (27.5%) had begun >1 week prior to delivery, and the longest onset was 28 days before delivery. The postpartum conditions of the women were stable, and no critical illness or death occurred.
None of the newborns showed fever or respiratory distress during hospitalization. Detection of SARS-CoV-2 nucleic acid in pharyngeal swabs was negative. Except for the low level of CD16-CD56 cells, the count and proportion of lymphocytes, CD3, CD4, CD8, and CD19 were all normal. Moreover, serum immunoglobulin (Ig)G and M were within the normal range but interleukin (IL)-6 levels were increased. No correlation was found between maternal COVID-19 duration and the lymphocyte subsets or cytokine levels.
One infant was found to have an extremely elevated IL-6 concentration and developed necrotizing enterocolitis in the third week after birth. The remaining 50 infants did not show abnormal symptoms through the end of the follow-up period.
“To the best of our knowledge, this study is the first comprehensive and large-scale assessment report on the immune status of this population,” the authors stated. “The results from this study may further help us understand the immune function of newborns delivered by mothers infected with SARS-CoV-2 and improve treatment strategies and prevention.”
Liu P, Zheng J, Yang P, et al. The immunologic status of newborns born to SARS-CoV2-infected mothers in Wuhan, China [published online May 10, 2020]. J Allergy Clin Immunol. doi: 10.1016/j.jaci.2020.04.038.