Coronavirus Disease 2019 (COVID-19) Vaccination and Spontaneous Abortion

To examine the association between coronavirus disease 2019 (COVID-19) vaccination and spontaneous abortion.

We conducted a case-control study of clinically adjudicated spontaneous abortions (case group) occurring between January 19, 2021, and October 27, 2021, and live births (control group). Patients aged 16-49 years at eight Vaccine Safety Datalink sites who had singleton pregnancies, one or more prenatal visits, continuous health plan enrollment, and spontaneous abortion (fetal loss between 6 and less than 20 weeks of gestation) or live birth were eligible. A random sample of eligible patients with spontaneous abortions was adjudicated to confirm pregnancy outcome, outcome date, and gestational age at fetal death; patients in the adjudicated spontaneous abortion case group were matched 1:2 on Vaccine Safety Datalink site, maternal age, and pregnancy start date with eligible patients with live births. Vaccine exposure was considered from pregnancy start to spontaneous abortion date or equivalent gestational age for the matched live births (index date). Conditional logistic regression was used to evaluate the association between COVID-19 vaccination in pregnancy and spontaneous abortion; secondary analyses explored associations by dose number, vaccine manufacturer, and vaccination within 6 weeks of the spontaneous abortion.

Matched analyses included 296 patients in the spontaneous abortion case group and 592 in the live birth control group. There was no association between spontaneous abortion and COVID-19 vaccination (adjusted odds ratio [aOR] 0.85, 95% CI, 0.56-1.30). There was also no association between spontaneous abortion and dose number compared with no vaccine (one dose: aOR 0.81, 95% CI, 0.39-1.70; two doses: aOR 0.84, 95% CI, 0.51-1.38; vaccine manufacturer: Moderna aOR 0.59, 95% CI, 0.29-1.19 and Pfizer-BioNTech aOR 0.97, 95% CI, 0.57-1.66; or vaccine exposure window of 6 weeks before spontaneous abortion or index date: aOR 0.87, 95% CI, 0.53-1.44).

There was no observed association between COVID-19 vaccination in pregnancy and spontaneous abortion. Findings support the safety of COVID-19 vaccination in early pregnancy.