Interpretation
Our findings are not in concordance with what has been reported in the
early series of deliveries among COVID-19 infected women. Indeed,
caesarean section rate ranges from 86% to 91% in the earlier series of
cases(6,11). In a multicentre
study(11) from China including 99 deliveries, the
caesarean section rate was 86%, mostly for maternal pneumonia (39%),
although only in 7% of them it was severe. In a systematic
review(6) including 86 births mainly from China, but
also from USA, Sweden and Corea, a caesarean section was performed in
91% of the deliveries, and fetal distress was found a main contributor
to this exceedingly high rate. We found an overall caesarean section
rate of 34%, which is in keeping with the one reported in two more
recent retrospective multicentre studies, one in New-York involving 18
deliveries(18) and the other in Northern Italy with
42(19) (caesarean section rate of 42% and 43%,
respectively). Also in agreement with our results, both studies found
overall good maternal and neonatal outcomes. In fact, the caesarean rate
observed in our cohort after excluding those women who were delivered
preterm because of worsening of maternal respiratory status, was similar
(4/18, 22.2%) to our baseline caesarean rate expected as a tertiary
center (25.8%). Therefore, our findings support current recommendations
on that the mode of delivery in respiratory stable women should be taken
depending on obstetric conditions.
It could also be argued that concerns on the risk of vertical
transmission during vaginal delivery may have contributed to these
initially reported increased rates of caesarean section. However, in
previous epidemics of other coronavirus diseases, SARS and MERS,
vertical transmission was not confirmed although the evidence against
relies on a limited number of small series(20). It is
well known that vaginal route increases the risk of transmission through
cervical and vaginal contaminated secretions, as in the case of herpes
simplex or HIV viruses. However, SARS-CoV-2 is a respiratory virus that
mainly replicates in the respiratory tract and it has not been detected
in genital secretions(21) . Another potential way of
intrapartum transmission could be through contaminated stool since
SARS-CoV-19 RNA has been isolated from feces, but those are probably not
infectious forms of the virus(22). Bloodstream
transplacental transmission during uterine life or through placental
disruption at the time of delivery is also very unlikely, given that
viremia is uncommon. A single positive RNA-PCR reported case in amniotic
fluid in a 32 weeks preterm newborn delivered by caesarean section at
the time of very severe maternal infection could correspond to a true
vertical transmission secondary to a high maternal viremia or
inflammatory placental abnormality in this critically ill mother.
However, since amniotic fluid was collected for testing during the
caesarean section, maternal contamination could not be
excluded(10). Early-onset symptoms in the newborn, and
negative PCR at birth, but positive some days after, also suggests a
true vertical transmission, although horizontal or iatrogenic
transmission could not be discarded. Moreover, 2 articles reporting 3
neonates from mothers with COVID-19 and positive IgM
antibodies(23)(24) is also of concern, given that IgM
antibodies do not cross the placenta and are of fetal origin. However,
IgM antibodies assays have false positives, and the tests performed in
these studies lacked standardization(25).
In our study, in which newborns were swabbed in the first 48 hours of
life, we did not observe any positive RT-PCR in nasopharyngeal samples
irrespectively of the way of delivery. Likewise, Yan et al. in the
largest series reported so far described negative results of neonatal
SARS-CoV-2 PCR in all 86 tested cases(11). In the ten
samples of amniotic fluid and cord blood tested, they could not
demonstrate the presence of SARS-CoV-2. As far as we know there are no
reported positive newborns after vaginal deliveries. These findings
suggest that vaginal delivery is associated with a low risk of
intrapartum SARS‐Cov‐2 transmission to the newborn.