I don’t think there is great science on this but here’s a paper focusing on tactics to preserve fertility https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6626312/. It gives rates as high as 100% for mtf fertility (and as low as 25). And I may have missed it, but doesn’t seem to for trans men. Stories of trans men pausing hormones to have a kid are anecdotally pretty common though