A study looking at health data across the entire population of Scotland found that pregnant women who had not been vaccinated against COVID-19 and caught the disease were much more likely to suffer severe complications — for themselves and their infants — than those who had been vaccinated and got COVID. Yet despite the growing evidence, vaccination rates among pregnant women remained much lower compared to the general population.

"We really want to advocate for clear and consistent public health messaging and that's so that doctors and midwives and healthcare professionals can give the right advice to women," Dr. Sarah Stock, one of the authors of the study, said. "This advice needs to go out to partners and parents and grandparents and friends, so people can recognize that vaccination in pregnancy is the safest and most effective way for pregnant women to protect themselves and their babies."

Scientists from Scotland's public health agency and the University of Edinburgh looked at data on every recognized pregnancy in Scotland between March 2020 and October 2021 — 145,424 pregnancies — along with data on PCR test results and vaccinations. The findings are published in the journal Nature Medicine.

Between December 2020, when it became more regular to test for COVID during maternity care in Scotland, and October 2021, there were 4,950 confirmed infections in pregnant women in the country. Over 90% of the COVID infections that were associated with a hospital admission were in unvaccinated women, and of the 104 who ended up in critical care, 98.1% were unvaccinated.

The rate of perinatal deaths, meaning infant deaths in the later stages of pregnancy or shortly after birth, in women who got COVID while pregnant was much higher compared to the general population — 22.6 deaths per 1,000 births, versus a background rate of 5.6 per 1,000 births. And according to the study, all of the perinatal deaths following COVID infection involved women who had not been vaccinated. The rate of perinatal death remained near normal levels for women who had received COVID vaccines.

But despite these much better outcomes with vaccination, researchers found that, as of October, only 32% of pregnant women in Scotland had received two COVID vaccine doses by the time they gave birth, compared to 77% of non-pregnant women of childbearing age. 

In the U.S., the latest figures from the Centers for Disease Control and Prevention show about 42% of pregnant people are fully vaccinated, compared to 73% of all those aged 18 and up.

"I think for pregnant women, it has been a bit of a confusing story so far. So initially, there were concerns around vaccination of pregnant women," Dr. Aziz Sheikh, one of the authors of the study, told journalists. Many of those concerns had to do with how medical trials are conducted, and the fact that pregnant women aren't always included in early trials. 

But since the vaccines first rolled out, additional data from thousands of women has shown the vaccines are safe and effective in pregnancy. The CDC "strongly recommends" vaccination before or during pregnancy. 

"The key take-home message that we'd love to get across is that, really, the best way to protect both mother and baby is vaccination at the earliest opportunity," Sheikh said.