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Risk of Pregnancy Loss Prior to 20 weeks Gestation with COVID-19

Our take —

This research letter reported on the findings from a prospective study of 109 symptomatic pregnant people under investigation for COVID-19 in the United States who enrolled in the PRIORITY study before 14 weeks of gestation. The study found that miscarriage following symptoms of illness among participants with a positive SARS-CoV-2 PCR test (n=94) was similar to those with a negative SARS-CoV-2 PCR test (n=19, ~6-7%). While these findings, like much of the available evidence on COVID-19 in early pregnancy, are limited by a small sample size, potential selection bias, and incomplete adjustment for confounding factors, it is reassuring that none of the studies to date have implicated COVID-19 as a risk factor for miscarriage.

Study design

Prospective Cohort

Study population and setting

This study is a sub-analysis that included data from 109 women (13 years or older) enrolled in a prospective cohort of COVID-19 during pregnancy during the United States (Pregnancy CoRonavIrus Outcomes RegIsTrY — PRIORITY) before 14 weeks gestation. Participants could self-enroll or be referred from prenatal clinicians across the United States. Participants were screened and consented by phone. After enrollment, participants completed questionnaires weekly for four weeks following enrollment, and the authors calculated the crude cumulative incidence of pregnancy loss before 20 weeks gestation.

Summary of Main Findings

All 109 participants (mean age 31 years, 30% Latinx, mean gestational age between 9 and 10 weeks) were symptomatic, however, 94 tested positive for COVID-19 and 15 tested negative. Participants who tested positive were more likely to identify as Latinx (35.1% versus 20%) and report more previous pregnancies and living children (mean gravida 2.68, parity 1.02 versus gradiva 1.87, parity 0.47). There were no notable differences in pregnancy loss in those who tested positive or negative for COVID-19. Six of 94 participants with COVID-19 experienced pregnancy loss (6.4%, 95% CI 2.4, 13.4%) versus 1 of 15 participants who tested negative for COVID-19 (6.7%, 95% CI 0.1%, 31.9%).

Study Strengths

This study collected data prospectively, limiting the impact of recall bias.


This US-based study only included 109 participants in total, with only 15 in the comparison group. Given that the PRIORITY study enrolled participants partially via self-enrollment and the authors did not report the enrollment breakdown in this study, it is possible that only the most health-conscious pregnant people enrolled earlier than 14 weeks gestation (for example, only 1 participant reported current smoking). If more health-conscious individuals are also more likely to have better health outcomes (pregnancy loss in this study, 6.4%, is lower than the pre-pandemic known miscarriage rate of 10%, though this risk is not constant over gestational age and most women enrolled after the period of highest miscarriage risk), then these findings may not apply to the overall pregnant population in the US. Finally, the comparison of miscarriage between groups was descriptive and did not adjust for potential confounders including gestational age, previous pregnancy loss, maternal age, COVID-19 severity, and medication or drug use.

Value added

This study included pregnant persons with symptomatic COVID-19 disease primarily within the first trimester, a group for whom limited outcome data has been published. This study sought to examine a question of high clinical relevance for people interested in pursuing pregnancy during the COVID-19 pandemic.

This review was posted on: 18 July 2021