We still have a long ways to go before fully understanding the potential effects of Covid-19 on pregnant women and their infants but based on data to date the disease severity seems similar to that of non-pregnant people and vertical transmission seems rare.
In one of the larger studies involving 158 obstetric patients with Covid-19 from New York City, ~80% had mild or asymptomatic disease with the rest manifesting moderate or severe disease (1). Cough and fever were common symptoms in both groups. Women with moderate/severe disease were more likely to have comorbidities (eg, asthma) and were also more likely to have dyspnea and chest pain/pressure. Other symptoms included muscle aches, sore throat, congestion, headache, diarrhea, nausea and loss of taste or smell. Two women had pre-term delivery because of clinical status deterioration; there were no reported deaths. The generally favorable course of Covid-19 among pregnant women has been supported by other studies (2,3,4).
To date, vertical transmission of SARS-CoV-2, the agent of Covid-19 appears rare (2,3,5,6). In one review, only 1 of 75 newborns tested for SARS-CoV-2 infection were positive; this infant did well clinically but had transient lymphocytopenia and abnormal liver function tests (2). A systematic review found no evidence of intrauterine transmission of SARS-CoV-2 (6).
Transmission of SARS-CoV-2 during the first trimester may be unlikely because of expression of ACE2 (a receptor for the virus) in the trophoblasts is very low between 6-14 weeks (7). In a small study examining placenta and fetal membranes in Covid-19 women, 3/11 samples were positive for SARS-CoV-2 but none of the infants tested positive on day 1-5 of life or demonstrated symptoms of Covid-19 (8).
Although another source of perinatal infection is exposure to mother’s secretions during vaginal delivery, so far presence of SARS-CoV-2 in vaginal secretions has not been reported (8). Also encouraging is a study of 18 infants born of women testing positive for SARS-CoV-2, all of whom had normal APGAR scores, with the majority (>80%) testing negative (3).
So overall, the major threat of Covid-19 to the fetus appears to be the severity of illness in the mother. Pregnant women should be familiar with the early symptoms of Covid-19 and seek medical care as soon as possible.
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References
1. Andrikopoulou M, Madden N, Wen T, et al. Symptoms and critical illness among obstetric patients with coronavirus disease 2019 (COVID-19) infection. OB GYN 2020 https://pubmed.ncbi.nlm.nih.gov/32459701/
2. Zaigham M, Andersson O. Maternal and perinatal outcomes with COVID-19: a systematic review of 108 pregnancies. Acta Obstet Gynecol Scand 2020;00:1-7. https://pubmed.ncbi.nlm.nih.gov/32259279/
3. Breslin N, Baptiste C, Gyamfi-Bannerman C, et al. Coronavirus disease 2019 infection among asymptomatic and symptomatic pregnant women: two weeks of confirmed presentations to an affiliated pair of New York City hospitals. Am J Obstet Gynecol MFM 2020;100118. https://www.sciencedirect.com/science/article/pii/S2589933320300483
4. Chen L, Li Q, Zheng D, et al. Clinical characteristics of pregnant women with Covid-19 in Wuhan, China. N Engl J Med 2020, April 17. https://www.nejm.org/doi/full/10.1056/NEJMc2009226?af=R&rss=currentIssue
5. Di Mascio D, Khalil A, Saccone G, et al. Outcome of coronavirus spectrum infections (SARS, MERS, COVID-19) during pregnancy: a systematic review and meta-analysis. Am J OB GYN 2020. https://www.sciencedirect.com/science/article/pii/S0002937820305585
6. Yang Z, Liu Y. Vertical transmission of severe acute respiratory syndrome coronavirus 2: A systematic review. Am J Perinatol 2020;10.1055/s-0040-1712161. https://pubmed.ncbi.nlm.nih.gov/32403141/
7. Amouroux A, Attie-Bitach, Martinovic J, et al. Evidence for and against vertical transmission for SARS-CoV-2 (COVID-19). Am J OB GYN 2020. https://www.sciencedirect.com/science/article/pii/S000293782030524X
8. Penfield CA, Brubaker SG, Lighter J. Detection of severe acute respiratory syndrome coronavirus 2 in placental and fetal membrane samples. Am J OB GYN MFM 2020. https://pubmed.ncbi.nlm.nih.gov/32391518/
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