(CNN) — The US Centers for Disease Control and Prevention issued an urgent recommendation Wednesday for pregnant women and those who have recently given birth to get vaccinated against coronavirus.

Women trying or planning to become pregnant and those who are breastfeeding should also be vaccinated — but only 31% of pregnant people have been vaccinated, the CDC said. The result: thousands of pregnant women in the hospital and more than 160 dead.

“CDC strongly recommends COVID-19 vaccination either before or during pregnancy because the benefits of vaccination outweigh known or potential risks,” the agency said in a health alert.

“As of September 27, 2021, more than 125,000 laboratory-confirmed COVID-19 cases have been reported in pregnant people, including more than 22,000 hospitalized cases and 161 deaths,” it added.

The CDC said 22 pregnant women had died in August alone– the worst month yet of the pandemic. “Data from the COVID-19-Associated Hospitalization Surveillance Network (COVID-NET) in 2021 indicate that approximately 97% of pregnant people hospitalized (either for illness or for labor and delivery) with confirmed SARS-CoV-2 infection were unvaccinated,” the health alert said.

The risk is not just to the mother. COVID-19 in pregnancy can cause preterm birth or babies born so sick they have to go straight to the neonatal intensive care unit, or NICU. “Other adverse pregnancy outcomes, such as stillbirth, have been reported,” the CDC said.

“Vaccination coverage is highest among Asian people who are pregnant (45.7%), but lower among Hispanic or Latino pregnant people (25%), and lowest among Black pregnant people (15.6%),” the CDC added in a statement.

“Pregnancy can be both a special time and also a stressful time — and pregnancy during a pandemic is an added concern for families. I strongly encourage those who are pregnant or considering pregnancy to talk with their healthcare provider about the protective benefits of the COVID-19 vaccine to keep their babies and themselves safe,” CDC Director Dr. Rochelle Walensky said in a statement.

On Tuesday, Walensky told a White House COVID-19 briefing that studies show COVID-19 vaccines are safe for pregnant women. Pregnant women are also urged to get flu shots.

“We are fortunate now to have extraordinary safety data with all of these vaccines. We know that pregnant women are at increased risk of severe disease, of hospitalization and ventilation,” Walensky told the briefing Tuesday.

“They’re also at increased risk for adverse events to their baby. We now have data that demonstrates that vaccines — in whatever time in pregnancy or lactating that they’re given — are actually safe and effective and have no adverse events to mom or to baby,” Walensky added.

“And we’ve actually seen that, in fact, some antibody from the vaccine traverses to the baby and in fact could potentially protect the baby.” Just as with flu, the immune system proteins activated in the mother’s body travel to her unborn child.

Last week, Dr. Dana Meaney Delman, the CDC’s lead on maternal immunization, told the CDC’s Advisory Committee on Immunization Practices about the worrying trends among pregnant women.

“We now see increased numbers of pregnant people admitted to the ICU in July and August,” Meaney Delman told the meeting. The trend has continued into September, she said.

“The deaths reported in August is the highest number of deaths reported in any month since the start of the pandemic,” Meaney Delman added.

“We know that pregnant people with COVID-19 can become very sick. Some will die, and many will experience pregnancy and neonatal complications.

“We know that because of COVID some children will grow up without their mothers. We know that COVID-19 vaccines are safe and effective. If you are pregnant, postpartum, breastfeeding, trying to get pregnant now or might become pregnant in the future, please get vaccinated.”

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