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New CDC study finds COVID-19 vaccines don’t cause preterm birth or small-for-gestational age birth

The study, co-authored by HealthPartners Institute, is the latest to show that COVID-19 vaccines are safe for pregnant people and their babies

January 4, 2022

Bloomington, Minn. – A new study shows that COVID-19 vaccines do not cause preterm birth or small-for-gestational age at birth, adding to a mounting body of research that strongly suggests the preventive shots are safe for people who are pregnant. The study was published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report and co-authored by HealthPartners Institute researchers.

“This data is reassuring and paints an even clearer picture about COVID-19 vaccine safety among pregnant people,” said Elyse Kharbanda, MD, senior author on the study and executive director of research with HealthPartners Institute. “I hope anyone who is unvaccinated and pregnant will look at this data, as well as the other data that’s available, and feel comfortable about getting vaccinated against the virus.”

The researchers looked at preterm births and small-for-gestational age births among more than 40,000 births that occurred after COVID-19 vaccines became available. Preterm birth is when a baby is born before the 37th week of pregnancy. Small-for-gestational age birth is when a baby’s weight at birth is below the 10th percentile for its gestational age. About 10,000 of these pregnant people had received one or more doses of a COVID-19 vaccine.

The adjusted rates for preterm birth and small-for-gestational age at birth were no higher among patients who were vaccinated during second and third trimesters than they were among unvaccinated patients, which suggests the vaccines are safe for pregnant women. Because vaccines were not widely available until February 2021, most pregnancies with first trimester vaccination had not delivered when data for this study was analyzed, so risks specific to first trimester vaccination could not be evaluated.

The pregnancy data came from HealthPartners and seven other large health systems that make up the Vaccine Safety Datalink (VSD). Vaccine Safety Datalink is a research network funded by the Centers for Disease Control and Prevention that conducts post-marketing surveillance of vaccines licensed and used in the United States. Kharbanda and colleagues previously published a study demonstrating that mRNA vaccines weren’t associated with miscarriage.

Meanwhile, other research is showing that COVID-19 infection during pregnancy increases the risk of severe disease for pregnant people, and may increase the risk of preterm birth and pose additional long term risks to the baby. These increased risks have prompted the world’s leading medical experts to recommend pregnant people get vaccinated against COVID-19.

“Many unvaccinated people who are pregnant have concerns about the vaccines, and some skepticism is understandable. But, getting infected with COVID-19 during pregnancy can result in severe disease,” Kharbanda said. “We now have the data to show that COVID-19 vaccines are safe for pregnant people, and COVID-19 infection is really unsafe for pregnant people. So, it’s important to consider vaccination if you’re pregnant.”

About HealthPartners Institute

HealthPartners Institute is part of HealthPartners, the largest consumer-governed, non-profit health care organization in the nation with a mission to improve health and well-being in partnership with members, patients and the community. HealthPartners Institute supports this mission through research, education and practice. The Institute annually conducts 400+ research studies and trains 700+ medical residents and fellows and 1,200+ medical and advanced practice students. Its integration with HealthPartners’ hospitals, clinics and health plan strengthens the Institute’s ability to discover and develop evidence-based solutions and translate them into practice. Based in Minneapolis, the Institute’s work impacts care, health and well-being across the region and nation as well as internationally. Visit for more information.

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