Symptomatic COVID-19 in first two trimesters associated with still, preterm birth risks

Among pregnant women with symptomatic COVID-19, SARS-CoV-2 infection during the first and second trimesters was associated with greater risks for stillbirth and preterm birth compared with infection during the third trimester, data show.

“SARS-CoV-2 infection during pregnancy results in higher risk of preterm births,” Antonella Iannaccone, MD, a faculty of medicine member at the University Hospital of Duisburg-Essen in Essen, Germany, and colleagues wrote in the American Journal of Obstetrics & Gynecology. “Recently, it has been shown that the gestational age at infection but not the severity of the infection has a significant impact on preterm birth rate. The aim of this study is to analyze the association of timing of symptomatic SARS-CoV-2 infection during pregnancy with preterm and stillbirth risk.”

Iannaccone and colleagues reviewed data from 113 hospitals in Germany and Austria that were reported in the prospective COVID-19-Related Obstetrics and Neonatal Outcome Study register. The researchers identified 1,149 pregnant women who had confirmed symptomatic COVID-19 before 37 weeks’ gestation between April 3, 2020, and Aug. 24, 2021.

To evaluate timing of infection, the researchers dichotomized exposure based on trimester of infection, with first or second trimester infections categorized as “early” and third trimester infections categorized as “late.”

Within the study population, there were 21 (1.8%) stillbirths and 201 (17.8%) preterm births. Most women were infected during the third trimester, with 45.5% having a first or second trimester infection.

In total, 17.8% of women delivered preterm, more than double the rate of preterm birth in the general population of Germany. Compared with women with late infection, those infected early in pregnancy had a greater risk for preterm birth at or before 32 weeks’ gestation (adjusted RR = 2.07; 95% CI, 1.1-3.91).

This finding conflicts with previous research that found an increased risk for preterm birth with infection late in pregnancy but not early in pregnancy vs. no infection.

Women infected early in pregnancy also had a greater risk for stillbirth compared with those infected in the third trimester (aRR = 2.76; 95% CI, 1.15-6.64).

Compared with early infections, late infections were associated with greater risks for threatened preterm birth (RR = 1.8; 95% CI, 1.07-3.01) and gestational cholestasis (RR = 3.18; 95% CI, 1.19-8.44).

The overall risk for preterm birth was greater within the 4 weeks after infection (RR = 4.89; 95% CI, 3.86-6.19).

Of note, none of the 1,084 women with a known vaccination status had been vaccinated against SARS-CoV-2 when they were infected, according to the researchers.

“Women with a symptomatic SARS-CoV-2 infection could profit most from an intensive obstetric surveillance,” Iannaccone and colleagues wrote. “A symptomatic SARS-CoV-2 infection increased pregnancy complications and should be prevented by vaccination.”