BACKGROUND AND PURPOSE: 

• Based on the WHO’s new criteria, vertical transmission is considered to have occurred if  
  • The mother is SARS-CoV-2 positive from 14 days before until 2 days after delivery 
  • The virus is detected in amniotic fluid, the placenta, or the neonate within the first 24 hours postpartum 
  • There is a viral presence in the neonate beyond 24 hours 
• Sevilla-Montoya et al. (Ultrasound in Obstetrics & Gynecology, 2021) investigated the possibility of vertical transmission in asymptomatic SARS-CoV-2-positive women using the WHO criteria 

METHODS: 

• Cohort study 
• Population  
  • Hospitalized for delivery 
  • Positive SARS-CoV-2 test 24 to 48 hours prior to delivery 
  • Asymptomatic at the time of the test 
  • Had an obstetric indication for cesarean 
• Study design 
  • Amniotic fluid was collected during cesarean, and neonatal oral and rectal swabs were collected at birth and 24 hours after birth 
• Primary outcome 
  • Vertical transmission, as defined by WHO criteria 

RESULTS: 

• 42 SARS-CoV-2 positive, asymptomatic women 
• Mothers who developed mild disease after discharge: 59% 
• Neonatal death: 7% (3 cases) 
  • Neonate SARS-CoV-2 positive at birth: 1 
  • Neonate had COVID-19 symptoms: zero 
• Cases with strong evidence of vertical transmission: 5 of 7 cases (11.9%)  
  • Amniotic fluid and neonatal samples were positive at birth and at 24 hours after birth 
  • 40 to 60% of infected neonates would not have been detected if only one swab (oral or rectal) was tested 
• Passive immunity 
  • IgG transfer from mother to neonate observed in 50% of cases in which maternal IgG was detected 

CONCLUSION: 

• Evidence of SARS-CoV-2 vertical transmission, as defined by the WHO, was found even in asymptomatic women 
• The authors state 

In conclusion, our data support that intrauterine transmission of SARS-CoV-2 is possible even in asymptomatic women. 

Testing for SARS-CoV-2 in both oral and rectal neonatal swabs improves considerably the detection rate, as compared with when only one swab is tested 

Learn More – Primary Sources: 

Evidence of possible SARS-CoV-2 vertical transmission according to World Health Organization criteria in asymptomatic pregnant women 

Related ObG Topics:

Vertical Transmission in Pregnancies with Confirmed COVID-19

Neonatal Infection: COVID-19 and Risk for Vertical Transmission

COVID-19 and Vertical Transmission: Best Practices and Subsequent Outcomes