Pre-Delta rates similar to pre-pandemic rates

Having Covid-19 during childbirth was associated with nearly double the risk for stillbirth delivery and more than a four-fold greater stillbirth risk during the period of SARS-CoV-2 Delta variant dominance in an analysis by researchers from the CDC.

The CDC researchers compared roughly 1.2 million deliveries among women without Covid-19 to just over 21,600 deliveries among those with documented Covid-19 during delivery, finding a stillbirth incidence of 0.64% and 1.26%, respectively, among the two groups.

The study was published online in the CDC’s Morbidity and Mortality Weekly Report.

“This analysis adds to growing evidence of an association between Covid-19 in pregnancy and stillbirth, highlights that the risk for stillbirth associated with Covid-19 is affected by maternal morbidity, and demonstrates that the risk has increased during the Delta period,” wrote CDC researcher Carla DeSisto, PhD, and colleagues.

They noted that the pre-pandemic stillbirth rate of 0.64% reported in their study is similar to widely reported pre-pandemic rates, including the most recent report on fetal deaths in the U.S. from the U.S. Health and Human Services Department showing a stillbirth rate of 0.59%.

Early data examining the impact of Covid-19 on stillbirth have been inconclusive, DeSisto et al wrote, with one analysis of data from the Premier Healthcare Database from March to September of 2020 showing no increase in stillbirth risk.

Two meta-analyses, however, did suggest a link between Covid-19 and stillbirth, but adjustment for potential confounders was lacking in both, the researchers noted.

The CDC researchers included an additional year of Covid-19 pandemic data, “adding to the growing evidence that Covid-19 is associated with an increased risk for stillbirth,” DeSisto and colleagues wrote.

They analyzed Premier Health Database Special Covid-19 Release (PhD-SR) data from March 2020 through September 2021 to compare stillbirth incidence before and during the Covid-19 pandemic, as well as before (March 2020-June 2021) and during (July-September 2021) the period of Delta variant predominance.

“To better understand the potential biologic mechanism for stillbirth among women with Covid-19 at delivery, Poisson regression models with robust SEs were used to calculate unadjusted and adjusted prevalence ratios for stillbirth for each underlying medical condition and indicator of severe illness among deliveries with documented Covid-19,” the researchers wrote.

Among 1,249,634 deliveries at 736 hospitals during March 2020–September 2021 (53.7% of mothers were non-Hispanic White, and 50.6% had private insurance), a total of 21,653 women (1.73%) had documented Covid-19 at delivery.

“During March 2020–September 2021, a total of 8,154 stillbirths were documented, affecting 0.64% and 1.26% of deliveries without Covid-19 and with Covid-19, respectively (aRR=1.90; 95% CI=1.69–2.15),” the study authors wrote. “During the pre-Delta period (March 2020–June 2021), 6,983 stillbirths were documented, involving 0.98% of deliveries with Covid-19 compared with 0.64% of deliveries without Covid-19 (aRR=1.47; 95% CI=1.27–1.71).”

However, stillbirths increased from July to September 2021, during the Delta period. The study authors wrote that “1,171 stillbirths were documented, involving 2.70% of deliveries with Covid-19 compared with 0.63% of deliveries without Covid-19 (aRR=4.04; 95% CI=3.28–4.97).”

Study limitations cited by the researchers included the necessary reliance on hospital records data to identify Covid-19, underlying medical conditions, gestational age and stillbirths; a lack of data on gestational age at SARS-CoV-2 infection; a lack of data on whether Covid-19 was symptomatic or asymptomatic; and the lack of whole generation sequencing to confirm SARS-CoV-2 variant status and vaccination status. DeSisto and colleagues concluded that additional prospective studies are needed to identify mechanisms associated with the observed findings, the contribution of maternal risk factors, and the impact of vaccination against Covid-19. They also called for studies exploring “differences in risks relative to the timing and severity of infection.”

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A separate study by CDC and Mississippi Department of Health investigators, also published in the November 19 MMWR, described the cases of 15 women in Mississippi who died from Covid-19 during pregnancy or soon after delivery between early March, 2020 and early October, 2021.

Six of the fatalities occurred before the emergence of Delta variant, and nine of the fatalities occurred after delta became the dominant variant in Mississippi and the U.S.

Nine of the women who died were Black, three were Hispanic, and three were White, and 14 of the 15 women had underlying medical conditions, including obesity (67%), hypertension (53%), diabetes (27%), and cancer (13%).

All the women were admitted to ICUs during their hospital stays, 14 (93%) underwent invasive mechanical ventilation, and 7 (47%) had emergency cesarean deliveries.

None of the 15 had been fully vaccinated against Covid-19, with five deaths occurring prior to vaccine availability and just one occurring among a partially vaccinated person.

“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 persons and Hispanic persons,” wrote Laurin Kaschagen, PhD, of the CDC and the Mississippi State Department of Health, and colleagues.

  1. Having Covid-19 during childbirth was associated with nearly double the risk for stillbirth delivery.

  2. The highest stillbirth risk was observed after delta became the dominant SARS-CoV-2 variant in the U.S.

Salynn Boyles, Contributing Writer, BreakingMED™

This study was conducted by CDC researchers. The researchers declared no relevant disclosures.

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