A large study recently undertaken by Adhikari et al. (2020) examined the risks of SARS-CoV-2 infection during pregnancy and delivery to the mother and child, finding that no severe adverse outcomes are expected to either party.
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Neonatal infection was found to be as common as 3% of children, birthed largely from asymptomatic or only mildly symptomatic women.
Why is this study important?
In June 2020 the CDC reported a higher rate of hospitalization among pregnant women diagnosed with COVID-19 compared with non-pregnant women, a stark figure of 31.5% compared to only 5.8%. However, at the time of publishing this data little was known with regards to the full reason behind hospitalization and details of illness severity, or indeed the probable outcomes to the children.
Early information suggested that adverse outcomes such as preterm birth, preeclampsia, and cesarean delivery were more common among SARS-CoV-2 infected women, and examination of the placentas raised concerns over observed inflammation and vasculopathy.
The group determined that a high-volume study of neonatal outcomes in infected individuals was warranted, selecting an urban maternity care center with easy access to SARS-CoV-2 testing as the site of examination.
In the period from March 18th to August 22nd, 2020, at Parkland Health and Hospital System (Dallas, Texas), 3,374 women gave birth, 252 of which tested positive for SARS-CoV-2 infection by reverse transcriptase-polymerase chain reaction testing. Of these 252, 239 (95%) were considered to be asymptomatic or exhibited only mild symptoms, with the remainder being severe or critical.
The group compared the trimester of diagnosis, course of the illness, delivery outcomes, and illness severity of the women. Additionally, the placentas of SARS-CoV-2 infection positive women were examined blindly by a pathologist, without knowing the stage or severity of the disease.
Of the infants born to SARS-CoV-2 infected women, three bore anomalies, none of which could be associated with the infection. Of the women diagnosed with SARS-CoV-2 infection that presented as asymptomatic or mild, 3% subsequently developed severe or critical illness, though there were no maternal deaths. In total, 6% of the 252 SARS-CoV-2-positive pregnant women were hospitalized due to COVID-19-associated pneumonia within 14 days of testing.
When outcomes were compared by illness severity it was noted that gestational or pregestational diabetes and pre-term delivery was somewhat higher among women with severe illness. Of the ten women in the study with a severe or critical illness, six, unfortunately, experienced pregnancy loss or preterm birth.
188 infants were tested, 6 of which tested positive for SARS-CoV-2. In each of these six cases the mother was diagnosed during the third trimester: four were asymptomatic, while one exhibited mild symptoms and one severe. Of these infants, 4 tested positive at 24 hours old and remained positive at 48 hours, and the remaining two tested positive only at the 48-hour point.
In one case intrauterine transmission was suspected as the placental tissue bore viral particles. The mother had developed pneumonia, and the infant exhibited febrile illness. However, in each of the other cases, the group could not be sure whether the virus had transmitted vertically or horizontally.
Overall, SARS-CoV-2–positive women did not have a notably higher instance of preterm birth, preeclampsia, or cesarean delivery due to abnormal fetal heart rate, and there were no significant differences in adverse pregnancy outcomes.
The authors note that the number of asymptomatic women in their study was lower than noted by some other similar but smaller-scale studies, though explain this discrepancy by the inclusion of women visiting the hospital in several in- and out-patient settings rather than only those admitted to the delivery unit.