There is no evidence that COVID-19 vaccination contribute to increased risk of spontaneous abortion (miscarriage).
Systematic review and meta-analysis of effectiveness and perinatal outcomes of Covid vaccination in pregnancy shows lowered risk of stillbirth by 15%. No difference in risk of miscarriage, preterm birth or NICU admission.
"Our findings suggest that the risk of spontaneous abortion after mRNA Covid-19 vaccination either before conception or during pregnancy is consistent with the expected risk of spontaneous abortion; these findings add to the accumulating evidence about the safety of mRNA Covid-19 vaccination in pregnancy."
In a study where 13,160 spontaneous abortions were identified from 105,446 unique pregnancies, "Among women with spontaneous abortions, the odds of COVID-19 vaccine exposure were not increased in the prior 28 days compared with women with ongoing pregnancies."
"Preliminary findings did not show obvious safety signals among pregnant persons who received mRNA Covid-19 vaccines."
The document (refer to page 12, table 6):
This document describes post authorization adverse event monitoring, not clinical trial results. By definition, only adverse events are counted and adverse events are not necessarily related to vaccination except temporally.
Adverse event data must always be subjected to additional study to determine if the rates are above the normal rate that would be expected for the population. There are many studies that show that if anything, vaccination reduces risk of miscarriage (see the Studies section of this page).
Actual rate of miscarriage among those who became pregnant during the Pfizer trial was 7% in the vaccine group (3 of 42 pregnancies) and 15% in the control group (7 of 47 pregnancies). https://www.fda.gov/media/152256/download (page 84)
"About 10 to 20 percent of known pregnancies end in miscarriage." https://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/symptoms-causes/syc-20354298