IE 11 is not supported. For an optimal experience visit our site on another browser.

Delta variant linked to increased risk of stillbirth, CDC study finds

Two new reports from the CDC suggest Covid's delta variant isn't just more contagious, it's also more dangerous to pregnant women and their babies.
Get more newsLiveon

Pregnant women who become infected with the delta variant are at increased risk of a stillbirth or dying during childbirth, according to two new studies published by the Centers for Disease Control and Prevention on Friday.

The research expands on reports from doctors nationwide who have noted an unprecedented rise in pregnant women becoming critically ill with Covid-19, particularly as the highly contagious variant has taken hold.

"We are seeing loads of pregnancy complications from Covid-19 infection," said Dr. Ellie Ragsdale, director of fetal intervention at UH Cleveland Medical Center.

Those complications include premature deliveries, abnormally high blood pressure in pregnant women, as well as pregnancy loss, said Ragsdale, who was not involved with the new research.

Full coverage of the Covid-19 pandemic

One of the new studies analyzed the outcomes of more than 1.2 million pregnancies nationwide between March 2020 and September of this year.

Stillbirths were rare in the United States before the pandemic, at a rate of .59 percent. Those rates remained similar even when the pandemic hit, at .64 percent among women who were never diagnosed with Covid.

But the rate of stillbirths rose to .98 percent among expectant mothers infected with the coronavirus, according to the CDC report.

And once the delta variant took hold in July this year, the rates rose exponentially: 2.7 percent of Covid-positive pregnancies ended in stillbirth.

"Although stillbirth was a rare outcome overall," the study authors wrote, documented Covid diagnosis was associated with a marked increase in the risk for stillbirth, "with a stronger association during the period of delta variant predominance."

The study doesn't prove the delta variant causes more fetal demise, but increasingly, obstetricians are documenting notable differences in how much oxygen fetuses can absorb, depending on whether their mothers have been diagnosed with Covid.

Ragsdale said she and her colleagues have noted that pregnant women with Covid have a difficult time getting oxygen-rich blood to their growing fetuses.

"We're seeing areas of the placenta that are oxygen deprived," she said. "That's the baby's source of oxygen and survival in pregnancy."

Download the NBC News app for full coverage of the Covid-19 pandemic

The CDC analysis didn't assess vaccination status, but unvaccinated pregnant women may be at particular risk, experts said.

As the delta variant took hold in July, the CDC said, just under a third of pregnant women had been vaccinated against Covid.

Among 34,016 Covid-positive pregnant women, 348 pregnancies were lost, the CDC reported.

What's more, the virus can also be deadly to the mother, particularly if she has an underlying health condition. A separate CDC report published Friday looked at 15 deaths among Covid-positive pregnant women in Mississippi. Nearly all had some kind of chronic health condition, such as high blood pressure or diabetes.

None had been fully vaccinated. In September, the CDC issued a health alert urging pregnant women to be vaccinated against Covid.

"We have evidence to show there is no increased risk of miscarriage or poor pregnancy outcomes from the vaccine," said Dr. Zsakeba Henderson, deputy chief medical and health officer for the March of Dimes. "All evidence points to the safety of this vaccine."

Follow NBC HEALTH on Twitter & Facebook.