Indigenous and Asian Pregnant People People with COVID Most at Risk for Preterm Birth in the US

Findings from the largest study of its kind support recommendations that all pregnant people receive vaccination against COVID-19

The largest US study on the relationship between COVID-19 diagnosis in pregnancy and preterm birth has revealed a disproportionate impact on birthing people of color.  

Previous studies have linked COVID infection to adverse birth outcomes, including preterm birth. But to date, there has been a lack of evidence from a large US population that allows examination into race/ethnicity, socioeconomic status and type of preterm birth. Now, a large study conducted by researchers at the UCSF California Preterm Birth Initiative has quantified these factors. The findings drawn from 240,000 births in California during the height of the pandemic were recently published in The Lancet Regional Health -Americas. 

Among the study results that pertain to COVID-19 diagnosis during pregnancy only, the researchers found a 3.7% reported a COVID-19 diagnosis in pregnancy and that diagnoses have continued to increase across all race/ethnicity groups. But diagnoses are disproportionately higher among people who are Latinx, American Indian/Alaska Native, Native Hawaiian/Pacific Islander and among those insured through Medicaid.  

Given the context that pregnant people may be trying to make decisions about their own risk and vaccination, having this risk established in a really large sample is important for providers and patients to have.

Deborah Karasek, PTBI researcher

Assistant Professor of Obstetrics and Gynecology at UCSF


The highest risk of preterm birth in those who have the COVID-19 was observed in American Indian/Alaskan Native birthing people. Asian birthing people were found to have the second-highest risk. The population of the sample was largely Latinx at 47.2% and the remainder were non-Latinx white at 26.8%, Black 4.9%, Asian 13.2%, American Indian/Alaskan Native .03%, and Hawaiian/Pacific Islander 0.4%. 

Those with a COVID-19 diagnosis had a preterm birthrate of 11.8% as compared with 8.7% among those without. In addition, a COVID-19 diagnosis was associated with an elevated risk of very preterm birth, preterm birth, and early-term birth.  

“The increase in Delta variant and this new surge is really making these findings even more timely right now,” said lead author Deborah Karasek, PTBI researcher and assistant professor of obstetrics and gynecology at UCSF. “Given the context that pregnant people may be trying to make decisions about their own risk and vaccination, having this risk established in a really large sample is important for providers and patients to have.” 

The study further supports the updated recommendation from American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine that all pregnant people receive vaccination against COVID-19. Though Karasek recognizes that, “BIPOC populations face unique and inequitable barriers to vaccine access as well apprehensions about vaccines due to historical trauma and medical mistreatment in a lot of these communities.”   

Going forward, Karasek shares that “what still has to be understood and addressed is the question of who is most sensitive to COVID infection and what are the surrounding risk factors that could lead to preterm birth, particularly with essential workers and the direct effect of policies such as shelter-in-place and workplace protections.” 

Although this study provides a clear indication of adverse outcomes associated with COVID-19 infection during pregnancy, the study does not reveal anything about the timing of infection or severity of infection. 

News Coverage of the Research

ABC 7 Bay Area News: COVID increases risk of premature birth in pregnant women, UCSF study shows. August 11, 2021.

Forbes: Covid-19 In Pregnant Women Endangers Unborn Children. August 10, 2021.

SF Chronicle: Devastating impact of COVID on pregnancy highlighted by large UCSF study. August 10, 2021.