No link between COVID-19 vaccination and preterm births or stillbirths: study

There is no link between COVID-19 vaccination during pregnancy and a higher risk of preterm birth or stillbirth, according to a new Ottawa-based study.

The population-based study led by the CHEO Research Institute, published in The BMJ, sheds new light on the risks and benefits of COVID-19

“Our study found no evidence of increased risk of preterm birth, very preterm birth, small-for-gestational-age at birth, or stillbirth following COVID-19 vaccination during pregnancy,” lead author Dr. Deshayne Fell, scientists at the CHEO Research Institute and associate professor at the University of Ottawa, said in a news release.

“The results of this study provide further evidence for care providers and pregnant people about the safety of COVID-19 vaccination during pregnancy.”

Researchers looked at more than 85,000 births between May 1 and Dec. 31, 2021, using the provincial birth registry based out of CHEO. They linked that information to the province’s COVID-19 immunization database.

Of those, more than 43,000 occurred in people who received one or more dose of a COVID-19 vaccine during pregnancy (nearly all received an mRNA vaccine, mainly Pfizer or Moderna).

The study found that vaccination during pregnancy was not associated with any increased risk of overall preterm birth (6.5% among vaccinated v 6.9% among unvaccinated), spontaneous preterm birth (3.7% v 4.4%), or very preterm birth (0.59% v 0.89%). No increase was found in risk of small for gestational age at birth (9.1% v 9.2%) or stillbirth (0.25% v 0.44%).

The findings were similar regardless of what stage in the pregnancy the vaccine was given, the number of doses, or which mRNA vaccine was received.

Researchers say a wide range of factors were taken into account, including the mother’s age at delivery, pre-pregnancy body mass index, reported smoking or substance use during

pregnancy, pre-existing health conditions, number of previous live births and stillbirths, area of residence and income.

COVID-19 infections during pregnancy have been associated with a higher risk of complications, including preterm birth and stillbirth.

The project was supported by the Public Health Agency of Canada through the Vaccine Surveillance Reference Group and the COVID-19 Immunity Task Force.

Researchers say there are still unanswered questions that need more work, such as COVID-19 vaccination around the time of conception and using non-mRNA vaccines during pregnancy.