https://www.fda.gov/media/152256/download
Here is the actual data on pregnant subjects during Pfizer’s vaccine trial. Roughly 7% of pregnant participants in the treatment arm of the trial suffered spontaneous abortion, a number in line with the background rate. For comparison, pregnant participants in the placebo arm of the trial suffered spontaneous abortion/miscarriage at roughly twice that rate.
I took this screenshot directly from the Pfizer vaccine BLA. (Biologic License Application), which is linked at the top.