What are the perinatal risks of SARS-CoV-2 infection in pregnancy?

Study strengths and weaknesses

Strengths include the large, EHR-based dataset from a single organization, allowing for granular analysis on patient comorbidities and outcomes (rather than only based on diagnosis codes, as is true of many other large databases), as well as focus on relevant perinatal outcomes and thoughtful statistical modeling. However, a significant challenge with this, and many other studies, is ascertainment of SARS-CoV-2 infections throughout pregnancy. Asymptomatic and mildly symptomatic women, who may not be as likely to have adverse pregnancy outcomes, can often be counted in the unaffected population, biasing study results toward increased risks of SARS-CoV-2. Although the findings stratified by implementation of universal testing (which captures a greater fraction of asymptomatic patients at admission for delivery), do not suggest risk mitigation with asymptomatic status, this analysis did not capture asymptomatic infections earlier in pregnancy, many of which might not be associated with perinatal risk.

Another challenge with such a dataset is that one cannot determine the severity of illness of each patient without manual review of each chart; however, other data that are easily abstracted from the EHR may serve as a proxy. For instance, of the 307 women with symptomatic COVID-19, 4 required respiratory support above nasal cannula. This suggests a low rate of severely ill women, and may explain some of the findings in the study, such as no differences in the rate of CD, hypertensive disorders of pregnancy, or stillbirth, but does not explain the increased risk of both medically indicated and spontaneous preterm birth, or the rates of acute respiratory distress syndrome and sepsis that drive the increased risk of severe maternal morbidity.

The CDC has published data on the risks of stillbirth from a large hospital-based administrative database for COVID-19 from Premier Healthcare.² In a cohort of over 1.2 million women admitted for delivery, including the timeframe of Ferrara et al’s study, COVID-19 was associated with a 2-fold increased risk of stillbirth, with higher risks noted with the delta variant. A rare outcome, stillbirth occurs in 6/1,000 births,⁷ which was the rate seen in Ferrara’s publication for both women with and without SARS-CoV-2 infection. The rare nature of the outcome may explain why a signal was not noted in the article of interest.

Translating data to patient counseling

Ferrara and colleagues’ study clearly confirms that COVID-19 infection has risks. Although many women with a COVID-19 infection in pregnancy may have an uncomplicated course, a favorable outcome is hard to predict with certainty. Risks of prematurity, VTE, organ dysfunction, and stillbirth from COVID-19 are rare but devastating complications. However, vaccinated women tend to incur far fewer adverse outcomes of COVID-19 in pregnancy, namely a 90% risk reduction in severe or critical COVID-19, with lower rates of ICU admissions and stillbirths.⁸ While these data strongly favor vaccination, we remain ill-advised on management strategies specifically to mitigate risk for the pregnancy once affected by COVID-19 infection. Thus, prevention with vaccination, mask wearing, and physical distancing remains a cornerstone of prenatal care in the current day. ●