Two new CDC studies link COVID-19 with heightened pregnancy complications.

According to one CDC study that looked at more than a million deliveries, COVID-19 increased the risks of stillbirths, with the highest increase coming after the new Delta variant arrived.

The Tennessee Department of Health says from March of 2020 to August of 2021, ICU admissions at delivery were also 4 x as high among women with COVID-19.

For one Chattanooga woman, the decision to get vaccinated in October was personal.

Cassie O’Neill says as a double organ transplant recipient her pregnancy was already more of a risk.

"The only way to continue to be healthy and need organ transplants is to always consult and listen to and follow advice very strictly. And that's exactly what I did," said O'Neill.

She followed the recommendations of her doctors and welcomed a healthy baby Cordelia in April.

"It's funny, my husband and I both say, this is the best stage she's been in. This is the best month, four months, five months, six months, seven months," said O'Neill.

While the family is now preparing to celebrate Cordelia’s first Thanksgiving, O’Neill remembers the uncertainty the pandemic brought while she was still expecting

"It's scary to be a first time mom and pregnant, you're so afraid that whatever you do is going to hurt your baby," said O'Neill.

The CDC says only about 35 percent of pregnant women are fully vaccinated, But the CDC does recommend vaccines for expecting mothers.

"Unfortunately, pregnant women are at an increased risk of severe disease both for themselves and their fetus if they get COVID infection," said Dr. Jennifer Thompson, Fellowship Program Director of Maternal Fetal Medicine at Vanderbilt University Medical Center.

A new CDC study looked at over a million deliveries. The data showed a higher risk of stillbirths for those with covid19 and that risk nearly tripled once the Delta variant came on the scene.

"The vaccine has not been associated with increased risk of miscarriage or stillbirth. However, we do know that COVID infection in and of itself, based on this new data and some other historical data that was mixed ,that there is increased risk of stillbirth associated with COVID infection," said Thompson.

Doctor Thompson says she's witnessed the complications COVID-19 can have for expecting mothers first hand.

"We saw a significant increase in ICU admissions, especially during the Delta variants. We saw our highest number of ICU admissions for pregnant patients during that delta time," said Thompson.

Thompson says in order to protect both the baby and mother, it’s important to consider vaccination. She encourages any expectant mother to ask their doctors about vaccination.

According to Thompson, studies have also shown that pregnant women who are vaccinated protect their babies after delivery as well.

Vaccination can provide antibodies to the baby while pregnant and some antibodies are transferred through breastmilk after delivery.