Two studies released recently by the CDC further confirm the importance of vaccination against Covid-19 during pregnancy and the need for those who are pregnant to take whatever measures are reasonably possible to otherwise reduce their risk of contracting SARS-CoV-2. One article reports on the risk of stillbirth among women with and without Covid-19 at delivery, and the other reports on Covid-19 association deaths after an infection during pregnancy in Mississippi women. Previous research has already established that people have a greater risk of severe disease and hospitalization if they have Covid-19 while pregnant, even if they don’t have other high-risk underlying conditions. These new findings, published in late November, extend that evidence base further by looking at stillbirths and maternal mortality.

Early Questions About Covid Vaccination During Pregnancy

Early in the vaccine rollout, questions arose about whether pregnant people should get vaccinated against Covid-19 when data didn’t exist regarding the safety of the vaccines during pregnancy. As a result, the vaccine manufacturers excluded pregnant individuals from enrolling in the trials. Although a couple dozen people became pregnant during the trials, there weren’t enough to provide statistically significant data about the vaccines’ safety during pregnancy.

At the time, the American College of Obstetricians and Gynecologists advised people to consider getting the vaccine because the evidence was accumulating regarding the greater risks of poor outcomes for people with Covid-19 who were pregnant. But the World Health Organization complicated that advice by recommending against vaccination during pregnancy. (The WHO reversed that advice at the end of January, just under two months after the first vaccines were authorized in the US.) Since August 2021, the CDC has formally recommended vaccination during pregnancy, and the American College of Obstetricians and Gynecologists (ACOG) does as well in recommendations updated as recently as December 2021. Both also recommend boosters during pregnancy when people become eligible for them.

Stillbirth Rates Higher With Delta Infections

Researchers used data from a hospital-based administrative database to investigate the risk of stillbirth with Covid infection from March 2020 through September 2021, both before and during the dominance of the Delta variant in the US. Over the entire study period, among approximately 1.2 million births, stillbirths occurred in 0.65% of pregnancies, including 1.26% among women with Covid-19 at delivery and 0.64% without Covid-19. These findings equated to nearly twice the risk of stillbirth if women had Covid-19 at delivery, but the difference between Delta and pre-Delta variants was stark.

Before Delta, from March 2020 to June 2021, the risk of stillbirth was 1.5 times greater with Covid-19 than without, but during Delta, from July-September 2021, the risk of stillbirth was four times greater with Covid-19 than without. The researchers note previous findings that SARS-CoV-2 was linked to placental problems, potentially caused by placental inflammation, that may account for the higher risk of stillbirth. In addition, those with hypertension or multiple pregnancies had a greater risk of stillbirth with a Covid infection. Still, the increased risk overall remained even after accounting for differences between hospitals and between women, including age, race/ethnicity, insurance type, obesity, diabetes, smoking status, hypertension, and multiple pregnancies. “These findings underscore the importance of Covid-19 prevention strategies, including vaccination before or during pregnancy,” the researchers concluded.

Maternal Mortality With Covid Infection

The second study is a case series looking specifically at 15 pregnant women who died from Covid-19 in Mississippi between March 2020 and October 2021. The report notes a substantial uptick in the maternal death rate with Delta infections, with five deaths per 1,000 SARS-CoV-2 infections pre-Delta to 25 deaths per pregnancy per 1,000 infections during Delta. The average age of the women in the case series was 30 years old, and the group included nine Black women, three White women, and three Hispanic women.

All the women required ICU admission, and 14 required invasive mechanical ventilation. The median time to death from symptom onset was 18 days. Three women died during pregnancy, resulting in a nine-week miscarriage and two stillbirths at 22 and 23 weeks gestation. The other 12 died a median of five days after live birth, including seven of the women who had an emergency cesarean delivery. All but one of the women had an underlying condition, and none had received monoclonal antibody treatment. In addition, none of the women had been fully vaccinated against Covid, though one had received one dose.

Although the population is too small to draw statistically significant conclusions, the study identifies a trend of a substantially greater increase in maternal mortality risk with Delta infections that other researchers will need to investigate with larger populations. As with the previous study, the authors address the importance of vaccination. “Given existing disparities in vaccination rates among pregnant women, partnerships to address vaccine access, hesitancy, or other concerns about vaccination can enhance fair and just access to Covid-19 vaccination, including among Black and Hispanic persons,” the authors concluded.