Introduction
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an RNA
virus that usually causes mild respiratory illness (Corona virus
disease; COVID-19) in humans. Severe illness can develop, especially in
high-risk populations, such as elderly, immunosuppressed patients, and
patients with comorbidities.
The SARS-CoV-2 virion has four structural proteins known as the spike,
envelope, membrane, and nucleocapsid proteins; the nucleocapsid protein
holds the RNA genome, and the spike, envelope and membrane proteins
create the viral envelope1.
Diagnosis of SARS-CoV-2 infection is based on reverse-transcription
polymerase chain reaction (RT-PCR) performed on nasopharyngeal
samples2. Serologic tests may also be used for
COVID-19 diagnosis. Anti-spike IgG and IgM and anti-nucleocapsid IgG
detection kits are commercially available. Time from positive SARS-CoV-2
nasopharyngeal swab correlated with SARS-CoV-2 IgG antibody levels and
antibody titers gradually decline within 6-9 months, until
stabilization3.
The effect of pregnancy on humoral response to SARS-CoV-2 infection as
well as the rate of vertical transmission are not fully understood. At
the beginning of the current COVID-19 pandemic, evidence pointed to a
lack of vertical transmission, as determined by amniocentesis, umbilical
cord blood, placenta, neonatal secretion and breast milk
sampling4-9. However, recent data, mostly from case
reports and case series, demonstrated the presence of SARS-CoV-2 in the
placenta10-12, positive RT-PCR of nasopharyngeal swabs
of newborns and evidence of seropositivity in
neonates13-17.
Evidence for vertical transmission is suggested in either positive
neonates for SARS-CoV-2 RT-PCR, the presence of IgM-type antibodies in
the newborn since these antibodies do not cross the placenta, and
positive neonatal IgG serology with seronegative mother.
The present study explored maternal humoral immune responses to
SARS-CoV-2 infection and the rate of vertical transmission.