SARS-CoV-2 Infection and COVID-19 Vaccination in Pregnancy
SARS-CoV-2 infection poses increased risks of poor outcomes during pregnancy, including preterm birth and stillbirth. Viruses that cause pneumonia, including severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), have long been known to be of particular concern during pregnancy. Initially, lockdowns and a tendency towards risk avoidance masked some of the increased risks associated with SARS-CoV-2 infection in pregnancy, but with the passing of time the risks have become clearer.
Obstetric Outcomes and Disease Severity
Pregnancy is associated with increased disease severity in those infected with SARS-CoV-2. A meta-analysis of 92 studies comparing outcomes for pregnant patients with COVID-19 with age and sex-matched non-pregnant patients with COVID-19 found that pregnancy increases the risk of needing intensive care, invasive ventilation and extracorporeal membrane oxygenation. A more recent meta-analysis of 111 studies found the following risks associated with infection:
- Maternal mortality: OR 3.08 (95% CI 1.5–6.3)
- Neonatal mortality: OR 3.35 (95% CI 1.07–10.5)
- Stillbirth: OR 2.36 (95% CI 1.24–4.46)
- Pre-eclampsia: OR 1.6 (95% CI 1.2–2.1)
- Premature delivery: OR 1.48 (95% CI 1.22–1.8)
- Intensive care (ICU): OR 2.13 (95% CI 1.54–2.95)
- Invasive ventilation: OR 2.59 (95% CI 2.28–2.94)
- Extracorporeal membrane oxygenation: OR 2.02 (95% CI 1.22–3.34)
The increased risk of preterm birth (PTB) associated with SARS-CoV-2 infection seems to be driven largely by iatrogenic PTBs, with doctors opting to deliver the infant to try to save the critically ill patient. Furthermore, there is evidence that both maternal and neonatal outcomes were worse during the Delta wave of the SARS-CoV-2 pandemic than in preceding periods.
Placental Effects and Vaccination
There is also developing concern over the effects of SARS-CoV-2 infection on the placenta, and these effects seem to vary between different viral variants. The increased risk of stillbirth and pre-eclampsia are more likely to be associated with inflammatory changes affecting the placenta. Despite these risks, many pregnant individuals have been reluctant to be vaccinated against the virus owing to safety concerns.
Although pregnant people were excluded from the first trials of COVID-19 vaccines, the pressing need to protect this group meant that the vaccines were rolled out to them in advance of the completion of clinical trials. We now have extensive real-world data confirming the safety and effectiveness of COVID-19 vaccination during pregnancy, although it will also be necessary to determine the effectiveness of these vaccines specifically against newly emerging viral variants, including Omicron.