Receipt of mRNA COVID-19 vaccines preconception and during pregnancy and risk of self-reported spontaneous abortions, CDC v-safe COVID-19 Vaccine Pregnancy Registry 2020-21.
Level 3 - non-randomized controlled study
Prospective observational cohort registry study without an internal unvaccinated control group
PubMed 34401872 · doi:10.21203/rs.3.rs-798175/v1
What was done
Participants enrolled in the voluntary CDC v-safe smartphone-based surveillance registry (2020–2021) who received at least one dose of an mRNA COVID-19 vaccine preconception or prior to 20 weeks' gestation were evaluated. Individuals who did not report a pregnancy loss before 6 completed weeks of gestation were included. Life-table methods were used to calculate the cumulative risk of spontaneous abortion (SAB) occurring from 6 to 19 completed weeks of gestation, with direct age standardization to a reference population.
What was found
Among 2,456 pregnant persons analyzed, the crude cumulative risk of SAB between 6 and 19 weeks' gestation was 14.1% (95% CI: 12.1, 16.1%). Following direct age standardization, the cumulative risk of SAB was 12.8% (95% CI: 10.8-14.8%), which falls within the expected baseline range of 11% to 16% reported for recognized pregnancies in high-income countries.
Why it matters
This study provides early prospective registry evidence that preconception or early-pregnancy mRNA COVID-19 vaccination does not increase the risk of spontaneous abortion above historical baseline rates.
Limits
Enrollment in the v-safe registry was voluntary and relied on self-reported outcomes via telephone follow-up. There was no concurrent unvaccinated control cohort, necessitating comparison to historical population estimates. Losses occurring prior to 6 completed weeks of gestation were excluded from the analysis.
Cited by
- supports A study of approximately 2,500 women who received a COVID-19 vaccine before 20 weeks of pregnancy found a miscarriage rate of 12.8%, which fell within the normal baseline range of 12.5% to 18.7%.