COVID-19 vaccination during pregnancy is not associated with complications such as preterm birth or smaller than normal weight of babies, according to a study.The researchers at the

Yale University in the US noted that pregnant people who contract COVID-19 have an increased risk of disease severity and death.

One barrier to vaccine acceptance is the concern that vaccination might disrupt pregnancy, they said.

The findings, published on Tuesday in a report by the US Centers for Disease Control and Prevention (CDC), is based on more than 40,000 pregnant individuals.

It shows that COVID-19 vaccination during pregnancy was not associated with preterm birth or small-for-gestational-age (SGA) when comparing vaccinated with unvaccinated pregnant people.

The trimester when the vaccination was received and the number of COVID-19 vaccine doses received were also not associated with increased risk of preterm birth or SGA, the researchers found.

"Getting vaccinated against COVID-19 is important for preventing severe illness in pregnant people," said Heather Lipkind, associate professor at the Yale School of Medicine and lead author of the study.

Preterm birth -- where babies are delivered earlier than 37 weeks -- and SG, in which babies are delivered smaller in size than normal for the gestational age, have been associated with a higher risk for infant death and disability.

The researchers used data from eight health care organisations to investigate the risk for preterm birth or SGA among vaccinated and unvaccinated pregnant women aged 16 to 49 years.

Among those included in the study, 10,064 individuals, or nearly 22 per cent, received at least one COVID-19 vaccine dose during pregnancy, researchers said.

As many as 98.3 per cent received vaccination during their second or third trimester while rest received it during their first trimester of pregnancy.

Almost 96 per cent of those vaccinated received an mRNA vaccine developed by Pfizer or Moderna.

The new findings add to the evidence that COVID-19 vaccination is safe during pregnancy, the researchers said.

Research into the drivers behind low vaccine acceptance among pregnant people has found that the most common concerns have been a lack of information about COVID-19 vaccine safety in pregnant people and potential harm to the foetus, they added.