COVID-19 infection in pregnancy raises a woman's risk of death sevenfold and significantly elevates her odds for needing intensive care, a new study finds.

Getting the virus during pregnancy also ups the likelihood of pneumonia, according to researchers at George Washington University in Washington, D.C.

"This study provides the most comprehensive evidence to date suggesting that COVID-19 is a threat during pregnancy," said lead author Emily Smith, an assistant professor of global health at the GW Milken Institute School of Public Health.

"Our findings underscore the importance of COVID-19 vaccination for all women of childbearing age," she said in a university news release.

Smith and her colleagues pooled patient data from 12 studies conducted in 12 countries, including the United States. These studies involved more than 13,000 pregnant women.

Compared to uninfected pregnant women, moms-to-be with COVID-19 infection not only had seven times higher risk of dying during pregnancy or childbirth, but were at three times greater risk of needing ICU admission.

They had about 15 times higher risk of needing ventilator treatment and about 23 times higher risk of developing pneumonia, which is a potentially life-threatening complication of COVID.

The pregnant women with COVID also had a five times higher risk of blood clots that can cause pain, swelling or other life-threatening complications.

The babies born to women who were infected with COVID also developed problems. They were almost twice as likely to be admitted to a neonatal ICU after birth, and had higher odds for preterm birth. Preterm babies are at high risk of having lifelong health problems, Smith said, including delays in early childhood cognitive development.

Many women of childbearing age remain unvaccinated in the United States and elsewhere, the study noted. Some women hesitate or refuse to get the vaccine or booster shot because they think the risks of having COVID are small for young women or are unsure about vaccine safety during pregnancy.

More than 80 countries still do not recommend that all pregnant and lactating women get the COVID vaccine, Smith said. This meta-analysis provides public health officials and the public with clear, consistent and compelling findings, she said.

"This study shows the risk of getting COVID-19 for both mother and baby," Smith said. "All countries, including the United States, should make access to COVID vaccines an urgent priority in order to save lives and prevent health problems."

The study findings were published Jan. 17 in BMJ Global Health. The research was funded by the Bill & Melinda Gates Foundation.