A coronavirus infection during pregnancy more than doubles the risk of serious complications or poor outcomes like preterm birth, sepsis and blood clots compared to those who weren’t infected, according to a new peer reviewed study published in JAMA Internal Medicine, adding to a growing body of research highlighting the potentially lethal consequences of Covid-19 during pregnancy that can be easily prevented through vaccination.

Pregnant people testing positive for Covid-19 were 2.5 times more likely to experience severe complications during pregnancy or delivery—at least one of 21 conditions including sepsis, kidney failure, heart attack and acute respiratory distress syndrome—compared to those without Covid, according to an analysis of health records for nearly 44,000 pregnant individuals at Kaiser Permanente Northern California during the first year of the pandemic.

More than 1,300 people in the study had Covid and were three times more likely to have blood clots and twice as likely to give birth prematurely as a result, the researchers found.

The Covid patients were more likely to have a medically indicated preterm birth than a spontaneous one, the researchers noted, and the risk for both types was higher during early, middle and late terms of pregnancy.

In contrast with results from other studies, the researchers did not find an increased risk for preeclampsia—a potentially serious problem that can cause high blood pressure or organ problems during pregnancy—after accounting for other possible explanations in the group or stillbirth, which they said could be down to the small sample size in the study and differences in the way each study was conducted.

Dr. Mara Greenberg, one of the study’s co-authors and a maternal-fetal medicine specialist with The Permanente Medical Group, said the findings, which come from a large and diverse study group, highlight the importance of vaccination as the “the most important thing people can do to protect themselves and their baby.”

The research adds to an overwhelming amount of evidence that shows pregnant people infected with Covid are at much higher risk of serious disease and death and far more likely to give birth early and face serious complications during pregnancy.

Despite the risks, many pregnant people are not vaccinated, something that can be at least partially attributed to false and misleading information about the vaccines’ impact on fertility or safety during pregnancy. Regulators and public health officials, including the CDC, strongly encourage pregnant people to get the shots and studies have consistently demonstrated their safety to parent and child.

The long-term impact of Covid exposure on children during pregnancy. The long-term health implications for a child’s growth and development after exposure to Covid during pregnancy are not known, the researchers said.

These children should be evaluated “during childhood and beyond,” the researchers noted. The increased risk for preterm birth is also a concern, the researchers noted, as this is associated with a wide array of possible short- and long-term issues including impaired brain development and metabolic complications.