COVID-19 severity does not differ by trimester, study says

Reviewed by Emily Henderson, B.Sc.Feb 4 2022

Research shows that pregnant people who contract COVID-19 are at increased risk of severe complications, including hospitalization, ventilation, and death, compared to pregnant people without COVID-19. However, little is known about how the timing of COVID-19 infection during pregnancy might impact a pregnant person's risk of developing severe symptoms.

In a new study to be presented today at the Society for Maternal-Fetal Medicine's (SMFM) annual meeting, The Pregnancy Meeting^™, which is being held virtually, researchers will unveil findings that suggest that the severity of COVID-19 does not differ by trimester.

Regardless of what trimester they are in, pregnant people are at risk of developing severe COVID illness."

Rachel Schell, MD, study author, maternal-fetal medicine fellow, University of Texas Southwestern Medical Center, Dallas

Researchers identified a group of pregnant people at a single urban hospital in Dallas, Parkland Hospital, and followed the progression of their COVID-19 symptoms.

From March 18, 2020 to May 31, 2021, 1,092 pregnant people were diagnosed with COVID-19. Sixty-seven people (6 percent) were diagnosed in the first trimester, 309 (28 percent) in the second trimester, and 716 (66 percent) in the third trimester. There were no significant demographic differences between the groups.

Across all trimesters, 993 out of 1092 people (90.9 percent) were either asymptomatic or had mild COVID-19 symptoms, and 35 out of 345 people (10.1 percent) who were initially asymptomatic developed moderate, severe, or critical symptoms.

Among pregnant patients who were initially asymptomatic or had mild symptoms in any trimester, 5 percent developed moderate, severe, or critical illness.

"This research is helpful for us in counseling patients who test positive for COVID," said another one of the study's authors, Emily Adhikari, MD, a maternal-fetal medicine subspecialist at the University of Texas Southwestern Medical Center and medical director of perinatal infectious diseases at Parkland Hospital. "There is no reason to be hesitant to get vaccinated because you are early in your pregnancy. You're still at risk of getting really sick from COVID in your first trimester."

Researchers are in the process of expanding their research to look at whether there are significant differences or changes in COVID severity by trimester due to the Delta variant.

SMFM, the Centers for Disease Control and Prevention (CDC), and the American College of Obstetricians and Gynecologists recommend all pregnant people get vaccinated against COVID-19, noting that the vaccines are safe and effective. Vaccination rates among pregnant people continue to remain low despite evidence showing vaccines can help to prevent severe illness during pregnancy. The latest figures from the CDC  show that fewer than 36 percent of pregnant people are vaccinated; vaccination rates are even lower among pregnant people who are Black and Hispanic.

The abstract has been published in the January 2022 supplement of the American Journal of Obstetrics and Gynecology (AJOG) and can be accessed at no cost on the AJOG website. To view the presentation of this abstract or other Pregnancy Meeting™ abstracts and events, visit the SMFM website or contact Karen Addis at [email protected] or 301-787-2394.