Discussion
Despite very few reported cases of neonatal COVID-19, it is an ongoing
discussion whether SARS-CoV-2 can be vertically transmitted from the
mother to the child during labor. As symptomatic women with COVID-19
have often been delivered by caesarean section it is still difficult to
evaluate whether vertical transmission is harmless or constitutes a
potential threat to the newborn which could be prevented by delivery by
caesarean section (1). Previously, three cohort studies with a total of
76 women, have reported three cases where SARS-CoV-2 was detected in
vaginal swabs (4–6), where only one of the three women was pregnant.
We present a single case of a pregnant woman who was clinically affected
by COVID-19 in week 26 gestation, where SARS-CoV-2 was also detected in
two vaginal swabs. This case raises concern that SARS-CoV-2 could be
vertically transmitted during labor, however the clinical implications
of the findings should be discussed.
The cycle threshold values were markedly higher for the vaginal swabs
than for the pharyngeal swabs, indicating that there was a lower
presence of viral DNA. A week after the symptoms had resolved,
SARS-CoV-2 could still be detected in a pharyngeal swab but not in
vaginal swabs. This might imply that intrapartum transmission is most
likely when the mother is symptomatic, and the infant is not yet
protected by maternal antibodies.
In the present case, there are several potential sources for the viral
presence in the vagina. Theoretically, the vaginal epithelium is not
abundant in angiotensin-converting enzyme 2 (ACE2) receptors, but they
are upregulated during pregnancy (2). Hence, viral replication in the
vaginal epithelium itself is possible as the coronavirus binds to their
target cells though the ACE2 receptors. Further, as the patient was
being treated with anticoagulants at the time and had a history of
vaginal bleeding during pregnancy, it is possible that viral RNA was
being exudated from the blood stream, instead of actually being released
by the vaginal epithelium itself. There is also potential of seminal
contamination (3), however the patient had had coitus three to four days
before the vaginal swab and her partner first tested positive a couple
of days after the patient experienced the first symptoms.
Despite the risk of vertical transmission of COVID-19 during labor
presumably being low (7,8) and with infants being very likely to have a
mild course of the disease should they become infected (1), we recommend
all women testing positive for SARS-CoV-2 in pharyngeal swabs to be
routinely tested with a vaginal swab to gain more knowledge regarding
presence and level of the viral load in both symptomatic and
asymptomatic women with active COVID-19 infection. We also suggest that
mode of delivery should be discussed with women at risk of going into
labor with a recently discovered COVID-19 infection, where passive
immunity of the baby is unlikely, especially in more severe cases, where
caesarean section may be preferable due to potentially higher viral load
in the vagina.