COVID-19 severity during pregnancy consistent across trimesters

The progression of COVID-19 disease during pregnancy from asymptomatic or mild symptoms to moderate, severe, or critical symptoms is consistent regardless of trimester, according to a prospective study presented at SMFM 2022.

“Moderate, severe, or critical illness develops in almost 10 percent of pregnant patients infected with the SARS-CoV-2 virus,” presented study author Dr Rachel Schell from the University of Texas Southwestern Medical Center, Dallas, Texas, US.

“The frequency of COVID-19 disease progression in pregnancy does not differ by trimester of diagnosis,” she said.

Study participants were 1,326 pregnant women with PCR-confirmed COVID-19 who delivered at the Parkland Health and Hospital System, Dallas, Texas, US, between March 18, 2020 and September 30, 2021. Of these, 8, 27, and 65 percent were diagnosed during the first, second, and third trimester, respectively (mean age 29.1, 28.3, and 27.5 years, respectively).

More than 85 percent were Hispanic, 24–28 percent were nulliparous, and mean BMI at presentation was 34 kg/m². Seven percent of patients in the first and second trimester and four percent in the third trimester had chronic hypertension, while 6, 4, and 2 percent in the first, second, and third trimester, respectively, had pregestational diabetes.

Hospitalization within 14 days of a positive COVID-19 test was more common among patients who were in their third trimester than those in their first or second trimester and was most frequently due to obstetric indications (90 percent of third trimester admissions). [SMFM 2022, abstract 5]

After excluding hospitalizations for obstetric indications, frequency of admission within 14 days of COVID-19 diagnosis was comparable across trimesters.

Of the 830 patients who had mild COVID-19 disease at diagnosis, 93 percent remained with mild symptoms, while 3.7, 2.5, and 0.6 percent progressed to moderate, severe, and critical illness, respectively. Of the 11 patients who had severe COVID-19 disease at diagnosis, 45 percent (n=5) progressed to critical disease.

A total of 436 patients were asymptomatic at diagnosis. Of these, 90 percent remained asymptomatic, while 0.6, 1.6, and 0.9 percent (n=3, 7, and 4) progressed to moderate, severe, and critical illness, respectively. The likelihood of developing symptoms did not vary by trimester (15, 14, and 10 percent in the first, second, and third trimester, respectively; p=0.54).

Of the patients who were asymptomatic or had mild disease at diagnosis, 6 percent progressed to moderate, severe, or critical illness, with no significant difference by trimester (4, 5, and 6 percent in the first, second, and third trimester, respectively; p=0.80).

Trimester at COVID-19 diagnosis did not appear to affect the maternal and neonatal outcomes assessed including severe preeclampsia, risk for Caesarean delivery, excess blood loss at delivery, preterm delivery (<37 weeks gestation), or low birth weight (<10^th centile).

Subgroup analysis suggested an increased prevalence of severe or critical illness during the surge of the delta strain compared with pre-delta (7.8 percent vs 4.2 percent; p=0.02). However, this increased prevalence did not significantly vary by trimester (eg, 8.5 percent vs 4.6 percent among those diagnosed in the third trimester; p=0.05).

Additional analysis following the introduction of COVID-19 vaccination in January 2021 showed that 83 percent of patients diagnosed with COVID-19 were unvaccinated.

“Although the rates of infection are comparable to the non-pregnant population, it is suggested that pregnant patients are at increased risk of severe to critical COVID-19–related illness. Furthermore, severe COVID-19 infection in pregnancy is associated with an increased risk for adverse maternal and neonatal outcomes,” said Schell.

“Regardless of what trimester they are in, pregnant people are at risk of developing severe COVID illness,” she continued.  

“This research is helpful for us in counselling patients who test positive for COVID,” added study author Dr Emily Adhikari, also from the University of Texas Southwestern Medical Center and medical director of perinatal infectious diseases at Parkland Hospital, who pointed out the importance of COVID-19 preventative measures.

“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,” she said.