Study design and participants
This is a retrospective cohort study done at Union Hospital, China from
15 Jan 2020 to 30 April 2020. A total of five cases were included in
this study. This study included three fully-recovered pregnant patients
confirmed with COVID-19 during the first or second trimester
(<28 weeks gestation). COVID-19 recovery criteria were defined
according to the World Health Organization interim guidance
criteria10 and the Chinese Clinical Guidance for
COVID-19 Pneumonia Diagnosis and Treatment11, which
are as follows: (1) normal or significantly improved chest computed
tomography (CT), (2) negative SARS-CoV-2 nucleic acid test, and (3)
negative SARS-CoV-2 serum IgM, and positive or negative IgG. Two
asymptomatic cases with positive IgG at the time of delivery were also
included. Case D and case E developed mild cold at 26 week and 27 weeks,
they did not seek medical attention. The symptoms improved after 1 week.
Clinical symptoms of COVID-19, laboratory results, CT imaging results,
treatment course, pregnancy outcomes, placental pathology, SARS-CoV-2
laboratory results, angiotensin-converting enzyme 2 (ACE2) expression,
and neonatal throat swabs and antibody tests were analysed.
We reviewed the medical records, laboratory results, and imaging
findings of the recruited cases from admission to postpartum. Laboratory
examination before admission includes SARS-CoV-2 pharyngeal swab and
serum antibody, and chest CT scan. Postpartum, neonatal throat swab,
umbilical cord blood antibody testing, and QT-PCR for SARS-CoV-2, and
placental pathology were performed. Laboratory confirmation of
SARS-CoV-2 infection was done. SARS-CoV-2 infection was confirmed using
real-time RT-PCR12.
This study was approved by the Medical Ethics Committee of the Union
Hospital, TongJi Medical College of HuaZhong University of Science and
Technology [2020, NO. 0144]. Written informed consent was obtained
from the patients before enrolment and during data collection.
The Serum antibody test: SARS-CoV-2 IgG and IgM Colloidal gold method
(Vazyme, NanJing, China) on 20 \(\mu\)ml plasma.
Pathological examination: Placental tissue specimens (Case A, B, C, D)
were fixed using 3.7% formaldehyde solution for 48 hours. Conventional
HE staining was performed after paraffin embedding, each slice was 4μm thick. All HE sections were observed and reviewed by one
attending physician and one associate chief physician. Using RT-PCR
method to detect SARS-CoV-2 in placental tissue: three wax blocks were
selected for SARS-CoV-2 detection in each case, and the samples to be
tested included the placental villi (including maternal and foetal
surfaces), foetal membrane and umbilical cord as far as possible.
Formaldehyde-fixed paraffin-embedded sample RNA separation kit and
SARS-CoV-2 detection kit were used (Aide biological medicine technology
co., Ltd, XiaMen, China). ACE2 Recombinant rabbit monoclonal antibody
(Clone No. BP6153, Bailing (Biolynx) Biotechnology Co., Ltd. Hangzhou,
China) was used to study the expression of ACE2 in the placenta.
ACE2 evaluation criteria: the area quartering method was 1, 2, 3, and 4
points. The staining intensity was 1 (weak), 2 (medium), and 3 (strong),
respectively. The total score was multiplied by each other.
Funding
Funding was provided by the National Natural Science Foundation of
China, Hubei Provincial Natural Science Foundation of China.