Pregnant women who develop Covid-19 during the first and second trimesters of pregnancy are at greater risk of preterm birth and stillbirth compared to women who become infected during the third trimester, according to a study published in the American Journal of Obstetrics & Gynecology.¹

Data of 1149 pregnant women with confirmed symptomatic SARS-CoV-2 infection before 37 weeks of gestation between April 3, 2020 and August 24, 2021 was reviewed in this study to find out the association between timing of infection during pregnancy and the odds of stillbirth or preterm birth. This information was sourced from the prospective COVID-19-Related Obstetrics and Neonatal Outcome Study (CRONOS) register, which houses data of 2650 women with confirmed SARS70 CoV-2 infection during pregnancy from 113 hospitals in Germany and Austria. Early exposure was categorized as infection during the first or second trimester, while infection during the third trimester was categorized as late exposure. Asymptomatic infections or infection after 37+0 weeks of gestation were excluded from the trial.

Most of the infections in the current study occurred during the late trimester, while around 46% occurred during the first or the second trimester. Majority (98.2%) were live births; of these 201 (17.8%) were preterm births. Twenty-one (1.8%) stillbirths were also recorded.

The rate of preterm birth in the current study was “more than double the rate in the general population of Germany, which is around 9%”, noted the authors. The risk of early preterm birth was 2-folds higher among women who got symptomatic Covid-19 during the first or second trimester of pregnancy compared to those who got infected during the third trimester with adjusted relative risk of 2.07. Likewise, stillbirths were more likely to occur in women with early exposure to infection vs those with late infection with aRR of 2.76.

Women with late infections were more likely to be at risk of threatened preterm birth with RR of 1.8  and gestational cholestasis with RR of 3.18. The overall risk for preterm birth was greater within the 4 weeks following the infection with RR of 4.89. The vaccination status was known for 1084 women; but none of them had been vaccinated at the time of infection.

This study has shown that women who developed symptomatic Covid-19 in early pregnancy were more likely to have obstetrical complications compared to women who acquired the infection in the later part of the pregnancy. Hence, pregnant women with Covid-19 need to be closely monitored. In addition to the preventive measures such as face masks, avoiding crowded public places, hand washing, physical distancing, pregnant women should also be encouraged to take the Covid-19 vaccine.

Reference

1. Iannaccone A, et al; CRONOS Network. Is the risk of still and preterm birth affected by the timing of symptomatic SARS-CoV-2 infection during pregnancy? - Data from the CRONOS Network, Germany. Am J Obstet Gynecol. 2022 Nov 29;S0002-9378(22)02207-4. doi: 10.1016/j.ajog.2022.11.1301.