Are pregnant women more vulnerable for COVID-19 than non-pregnant women?

Understandably, many women (and their partners, family members and friends) are currently asking this question. Perhaps you are worried for yourself or a pregnant friend, or maybe you are planning a pregnancy and want to know more beforehand. We will try to answer this question as well as possible, based on the current evidence:

  1. We will outline what is known about vulnerability to any viral infection in pregnancy. 
  2. What we know about the severity of COVID-19 in pregnancy will be described.
  3. Current government policies and clinical advice with regards to pregnancy and vulnerable groups will be discussed.

 

1. Do pregnant women have an increased risk of getting infected by viruses such as SARS-CoV-2 (that causes COVID-19)?

In short: pregnant women do not appear to have a higher risk of getting infected with respiratory viruses than non-pregnant women, although some infections may have more severe consequences.

Explanation

Fortunately, there is no general immunosuppression during pregnancy, since that would leave pregnant women very susceptible to infections. Instead, the mother’s immune responses are subtly altered. The higher levels of two pregnancy hormones, oestrogen and progesterone, are most likely involved in this phenomenon. These hormones alter maternal systems in positive ways to optimally support the unborn baby. [1, 2] Pregnancy is generally not associated with an increased risk of getting a viral infection by itself. [2,3] Moreover, the majority of maternal infections cannot cross the placenta to infect the baby. Specifically for COVID-19, there is no evidence that pregnancy increases susceptibility to infection. [4] 

Due to changes in the cardiovascular, pulmonary and immune systems some respiratory viral infections can sometimes be associated with more severe symptoms in pregnant women compared to non-pregnant women. [3, 4] A common example is the flu, caused by the influenza virus, which can be more severe in pregnant women. [1, 2] The increase in symptom severity has especially been associated with the third trimester. [1, 3]

One of the possible explanations for an increased severity may be that due to the higher hormone levels in pregnancy, the upper airways may become a bit swollen. [5] Also, the pregnant uterus may limit the expansion of the lungs. In itself this does not increase the risk of getting a respiratory infection, but it may lead to feeling breathless more easily than non-pregnant women. [1, 5] This leads us to the following question:

 

2. Is the course of COVID-19 more severe in pregnant women compared to non-pregnant women?

In short: so far, pregnancy does not appear to increase the risk of getting severe COVID-19.

Explanation

Current evidence suggests that pregnant women do not have an increased risk of becoming very ill compared to other healthy adults when they are infected with SARS-CoV-2; most will only have mild symptoms. [3, 4] Breslin et al [6] describe 43 pregnant women presenting to a New York hospital who also had COVID-19. The majority of these women were outpatients or were admitted for pregnancy-related reasons; only three were initially hospitalized because of COVID-19. At first, testing was performed when there were indications that a woman might have COVID-19 (symptoms, exposure or travel); later, all pregnant women were tested. Overall, they found that the severity of COVID-19 was comparable in pregnant women (86% mild, 9.3% severe, 4.7% critical) and non-pregnant persons. [6]

Sometimes pregnant women, just as other members of the general population, may have to be admitted to the hospital with COVID-19. A preprint article by Docherty et al [7] reports that of the 16,749 hospitalized UK patients with COVID-19 that were investigated, around 6% were pregnant. In the general population, a comparable percentage is thought to be pregnant, suggesting that pregnant women are not more often hospitalized due to COVID-19. Moreover, they report that pregnancy was not associated with an increased risk of dying with COVID-19. [7]

A preprint study by Knight et al. [8] on 427 hospitalised pregnant women with COVID-19 in the UK reports that the risk factors for hospital admission for pregnant women are similar to those for the general population. Also, they found that generally, those admitted to the hospital were in the third trimester of pregnancy. [8]

 

3. Does your government consider pregnant women to be vulnerable/high risk?

In short: guidance in each country varies depending on the stage of the COVID-19 pandemic as well as local health care systems.

Explanation

In the UK, pregnant women are considered to be part of the vulnerable group. [9] This was decided based on the principle “better safe than sorry” and not because there was any evidence that COVID-19 is more severe in pregnant women. [10] Notably, pregnant women with some types of heart disease are considered to be at especially high risk of severe COVID-19 symptoms; therefore, for these women additional measures are recommended by the UK government. [10]

In contrast, Dutch pregnant women are not considered to be part of the group at higher risk; no special measures are advised simply because a woman is pregnant. [11, 12] Of course, some pregnant women can be considered at higher risk if they share risk factors also seen to be important in the general population. [11]

Summary

Current evidence suggests that pregnant women and their babies are not at increased risk of severe disease during the COVID-19 pandemic. However keep in mind that every day new information is being published on COVID-19. The pandemic has only been running since December 2019, so we do not yet have information on outcomes for women who became pregnant since then.  Data on women who have completed pregnancies after becoming infected during their pregnancy is becoming available, but is still limited.  If you still have questions after reading this information, please go to your government’s website, ask your general practitioner or contact another healthcare provider.

 

References

  1. Mathad JS, Gupta A. Pulmonary Infections in Pregnancy. Semin Respir Crit Care Med 2017;38:174-184. doi: 10.1055/s-0037-1602375
  2. Kourtis AP, Read JS, Jamieson DJ. Pregnancy and infection. N Engl J Med. 2014;370(23):2211-8. doi: 10.1056/NEJMra1213566
  3. Royal College of Obstetricians and Gynaecologists (RCOG). Coronavirus (COVID-19) Infection in Pregnancy: Information for healthcare professionals. Version 9, published 13 May 2020 [internet]. Available from: https://www.rcog.org.uk/globalassets/documents/guidelines/2020-05-13-coronavirus-covid-19-infection-in-pregnancy.pdf (accessed on 20-05-2020)
  4. International Society of Ultrasound in Obstetrics and Gynecology (ISUOG). ISUOG Interim Guidance on 2019 novel coronavirus infection during pregnancy and puerperium: information for healthcare professionals. Ultrasound Obstet Gynecol 2020;55:700-708. doi: 10.1002/uog.22013
  5. Liu H, Wang LL, Zhao SJ, Kwak-Kim J, Mor G, Liao AH. Why are pregnant women susceptible to COVID-19? An immunological viewpoint. J Reprod Immunol. 2020;139:103122. doi: 10.1016/j.jri.2020.103122
  6. Breslin N, Baptiste C, Gyamfi-Bannerman C, Miller R, Martinez R, Bernstein K et al. COVID-19 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. doi: 10.1016/j.ajogmf.2020.100118.
  7. Docherty AB, Harrison EM, Green CA, et al. Features of 16,749 hospitalised UK patients with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol. medRxiv 2020:2020.04.23.20076042. doi: 10.1101/2020.04.23.20076042
  8. Knight M, Bunch K, Vousden N, et al. Characteristics and outcomes of pregnant women hospitalised with confirmed SARS-CoV-2 infection in the UK: a national cohort study using the UK Obstetric Surveillance System (UKOSS). 2020. Available from: https://www.medrxiv.org/content/10.1101/2020.05.08.20089268v1
  9. UK government. Guidance: Staying alert and safe (social distancing). Published 11 May 2020 [internet]. Available from: https://www.gov.uk/government/publications/staying-alert-and-safe-social-distancing/staying-alert-and-safe-social-distancing (accessed on 20-05-2020)
  10. Royal College of Obstetricians and Gynaecologists (RCOG). Coronavirus infection and pregnancy: information for pregnant women and their families. [internet] Available from: https://www.rcog.org.uk/en/guidelines-research-services/guidelines/coronavirus-pregnancy/covid-19-virus-infection-and-pregnancy/ (accessed on 20-05-2020)
  11. Rijksinstituut voor Volksgezondheid en Milieu (RIVM). Risicogroepen en COVID-19. [internet] Available from: https://www.rivm.nl/coronavirus-covid-19/risicogroepen (accessed on 20-05-2020)
  12. Rijksinstituut voor Volksgezondheid en Milieu (RIVM). Zwangerschap en COVID-19. [internet] Available from: https://www.rivm.nl/coronavirus-covid-19/zwangerschap (accessed on 20-05-2020)