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COVID-19 During Pregnancy Associated with Preterm Birth, UCSF-Led Study Finds

Pregnant people infected with COVID-19 face an increased risk of very preterm birth (VPTB), preterm birth (PTB) or early term birth, according to a large population-based study led by researchers at UC San Francisco. 

Risk of VPTB, which occurs at less than 32 weeks of gestation, was 60 percent higher for people infected with COVID-19 during pregnancy, while the risk of giving birth at less than 37 weeks was 40 percent higher for those with infection. The risk of PTB rose 160 percent among people infected with COVID-19 who had medical comorbidities. The study also found that people of color face a disproportionate risk of COVID-19 infection while pregnant.

“Preterm birth is associated with many challenging outcomes for pregnant people and babies, and very preterm births carry the highest risk of infant complications,” said the lead author of the study Deborah Karasek, PhD, MPH, an assistant professor in the Department of Obstetrics, Gynecology and Reproductive Sciences, and a researcher with the California Preterm Birth Initiative at UCSF.

“Our results point to the importance of preventative measures, including vaccination, to reduce COVID-19 infection among pregnant people to prevent preterm birth,” she said. “Pregnant people may have concerns about vaccines and the health of their babies, so being able to have an open dialogue that values those concerns, describes evidence about safety and conveys the risks posed by COVID-19 infection during pregnancy is critically important.”

ACOG and CDC recommend COVID-19 vaccines for pregnant people

In July 2021, the American College of Obstetricians and Gynecologists (ACOG) issued updated guidance strongly recommending that all pregnant individuals get vaccinated against COVID-19. In August 2021, the U.S. Centers for Disease Control and Prevention (CDC) also strongly recommended that people who are pregnant get vaccinated against COVID-19. Pregnant people are considered a high-risk population for COVID-19 infection, yet less than a quarter have received at least one dose of vaccine, according to the CDC. 

People of color face a disproportionate risk of COVID-19 infection while pregnant

The UCSF study was the first of its kind large enough to identify the risks of COVID-19 by specific subtype of PTB, as well as by race, ethnicity and insurance status. The study data reflected both existing disparities in PTB rates for people of color compared to rates for white people, and the known outsized burden of the pandemic on communities of color. Latinx, American Indian/Alaska Native, Native Hawaiian/Pacific Islander people and individuals with public insurance had disproportionately higher COVID-19 rates during pregnancy. For example, while 47 percent of pregnant people in the study were Latinx, they represented 72 percent of the people with COVID-19 diagnoses. 

“Given that the burden of COVID-19 is greater in these populations, as is the burden of pre-term birth, it really points to the need for an equity approach,” said Karasek. “With the surge in infections and increase in the Delta variant, we must think about pregnant people, especially Black and Brown populations, as the groups that need to be prioritized, with supportive policies to reduce exposure and stress and increase access to care.”

The researchers analyzed birth certificate data from all live births in California between July 2020 and January 2021. Of the 240,157 recorded births, nearly 9,000, or 3.7 percent, indicated a COVID-19 diagnosis in pregnancy. The PTB rate among birthing people with a COVID-19 diagnosis was 11.8 percent, compared with 8.7 percent among those without COVID-19. 

Risk of PTB is significantly higher for people with comorbidities

Having comorbidities along with COVID-19 infection increased the risk of PTB. Individuals with hypertension, diabetes and/or obesity as well as a COVID-19 diagnosis had a 160 percent higher risk of VPTB and a 100 percent higher risk of PTB compared to those without comorbidities or COVID-19.

Researchers found that PTB rates didn’t vary by whether the births were spontaneous or medically induced, which may indicate multiple pathways between COVID-19 infection and PTB. 

The study had limitations in that the stage of pregnancy during which the individuals contracted COVID-19 and the severity of illness were not included in the data. These are important details for understanding the mechanisms by which COVID-19 affects PTB risk. “These factors are currently being studied at UCSF and elsewhere,” Karasek said.

To learn more:

California Preterm Birth Initiative at UCSF

UCSF Obstetrics and Gynecology

Phone: (800) 444-2559 | Fax: (415) 353-4395

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