The Importance of Vaccination, Variants and Time Point of SARS-CoV-2 Infection in Pregnancy for Stillbirth and Preterm Birth Risk: An Analysis of the CRONOS Register Study

Abstract

Background: The risk of preterm birth (PTB) and stillbirth increases after a SARS-CoV-2 infection during gestation. We aimed to estimate the risk depending on gestational age at infection (early Methods: PTB was divided into early PTB (Results: Stillbirth and early preterm births rates were higher during the Alpha (1.56% and 3.13%) and Delta (1.56% and 3.44%) waves than during the Omicron wave (0.53% and 1.39%). Early SARS-CoV-2 infection increased the risk for stillbirth (aRR 5.76, 95% CI 3.07–10.83) and early PTB before 32 + 0 (aRR, 6.07, 95% CI 3.65–10.09). Hospital admission increased the risks further, especially in the case of ICU admission. Vaccination against SARS-CoV-2 significantly reduced the risk of stillbirth (aRR 0.32, 95% CI 0.16–0.83). Conclusions: This multicentric prospective study shows an increased risk of stillbirth and preterm birth after infection early in pregnancy and therefore the importance of obstetrical surveillance thereafter. Vaccination offers effective protection.

Keywords

• vaccination
• preterm birth
• stillbirth
• COVID -19
• SARS-CoV-2
• alpha