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.