- Epidemiological and transmission tendencies are like those seen in non-pregnant adults.
- Consistent with findings in non-pregnant adults, the cases were predominantly classified as mild or common in terms of severity.
- Lag time between onset of symptoms and diagnosis was directly related to the severity of the infection.
Transmission via the reproductive system :
- Samples must be collected promptly after delivery to have an optimal representation of the intrauterine state.
- Studies show no evidence of vertical transmission in Caesarean delivery in third trimester infections. The risk of vertical transmission in early pregnancy infection is undetermined.
- SARS-CoV-2 was not present in amniotic fluid nor in cord blood samples of 6 patients.
- SARS-CoV-2 was not present in the vaginal fluid of postmenopausal women with severe pneumonia, which suggests that risks of vertical transmission during vaginal delivery and sexual transmission are likely low.
- Transplacental transmission is not yet elucidated. Placental expression of ACE2 and damage caused by hypoxemia may be potential gateways for intrauterine infection.
- Small studies showed evidence of SARS-CoV-2 specific IgG and IgM antibodies in neonatal serum samples in three of seven cases. However, respiratory samples were negative and IgM testing is known to produce false positives. Further investigation is needed on the longitudinal changes in antibody levels.
- Comorbidities (preeclampsia, uterine scarring, gestational diabetes and hypertension, uterine atony) were not shown to increase risk of transmission to the foetus.
Note that certain claims are limited by the small sample sizes.
The epidemiology data comes from an analysis of 103 pregnant women with a confirmed (81) or suspected (22) diagnosis of COVID-19. These cases were disclosed to the China CDC (Chinese Center for Disease Control and Prevention) from January 16, 2020 to February 8, 2020.
The data on transmission via the reproductive system comes from multiple records. Chen H. et al. carried out a retrospective analysis of 9 pregnant women with confirmed COVID-19 pneumonia at the Zhongnan Hospital of Wuhan University in Wuhan,China between January 20, 2020 and January 31, 2020. Karimi-Zarchi M et al. conducted a literature review that included a total of 31 pregnant women. Mengmeng and al. conducted a small literature review and retrieved data about the role of ACE2 receptors in the maternal-fetal viral transmission of COVID-19. Schwartz D.A. et al.analyzed clinical, laboratory and transmission data in 38 infected pregnant women and their newborns. Qiu L. et al. retrospectively studied 10 postmenopausal women in the Tongji Zhonga Hospital ICU infected with severe pneumonia between February 4, 2020 and February 24, 2020. Schwartz and Dhaliwal compared the effects of respiratory RNA viruses (coronaviruses, hpiv, hmpv rsv, and influenza) on pregnancy and fetal outcomes. Wang C. et al. present the existing information on intrauterine transmission in their article. Zeng H. et al. analyzed clinical and laboratory results from six infected mothers and their newborns admitted to Zhongnan Hospital of Wuhan University.
Sources for epidemiology :
- Dong Y., Mo X., Hu Y., et al. (in press). Epidemiological and Transmission Patterns of Pregnant Women with 2019 Coronavirus Disease in China. The Lancet. Retrieved from http://dx.doi.org/10.2139/ssrn.3551330
Sources about transmission via the reproductive system :
- Chen H., Guo J., Wang C. et al. (2020). Clinical characteristics and intrauterine vertical transmission potential of COVID-19 infection in nine pregnant women:a retrospective review of medical records. The Lancet. https://doi.org/10.1016/S0140-6736(20)30360-3
- Karimi-Zarchi M., Neamatzadeh H., Dastgheib S.A. et al. (April 2, 2020). Vertical Transmission of Coronavirus Disease 19 (COVID-19) from Infected Pregnant Mothers to Neonates : A Review. Fetal and Pediatric Pathology. https://doi.org/10.1080/15513815.2020.1747120
- Mengmeng L., Chen L. and al. (April 16 2020) The SARS-CoV-2 receptor ACE2 expression of maternal-fetal interface and fetal organs by single-cell transcriptome study. PLoS One. https://doi.org/10.1371/journal.pone.0230295
- Schwartz, D.A. (2020). An Analysis of 38 Pregnant Women with COVID-19, Their Newborn Infants, and Maternal-Fetal Transmission of SARS-CoV-2: Maternal Coronavirus Infections and Pregnancy Outcomes. Archives of Pathology & Laboratory Medicine In-Press. https://doi.org/10.5858/arpa.2020-0901-SA
- Qiu L., Liu X., Xiao M. et al. (April 2, 2020). SARS-CoV-2 is not detectable in the vaginal fluid of women with severe COVID-19 infection. Clinical Infectious Diseases. https://doi.org/10.1093/cid/ciaa375
- Schwartz DA and Dhaliwal BS (2020) Infections in pregnancy with covid-19 and other respiratory rna virus diseases are rarely, if ever, transmitted to the fetus: experiences with coronaviruses, hpiv, hmpv rsv, and influenza. Archives of Pathology and Laboratory Medicine. https://doi.org/10.5858/arpa.2020-0211-SA
- Wang C., Zhou Y., Yang H. et al. (April 7, 2020). Intrauterine vertical transmission of SARS-CoV-2: what we know so far. Ultrasound in Obstetrics & Gynecology. https://doi.org/10.1002/uog.22045
- Zeng, H., Xu, C., Fan, J., Tang, Y., Deng, Q., Zhang, W., & Long, X. (March 26 2020). Antibodies in Infants Born to Mothers With COVID-19 Pneumonia. JAMA. https://doi.org/10.1001/jama.2020.4861