There is a risk of infertility with prolonged Hormone Replacement Therapy. However, even still, trans people do still achieve pregnancy (example, example, example, this guy was pregnant with his second baby post-HRT, this trans man used a trans woman’s sperm to get pregnant).
The likelihood of fertility post-HRT is currently unknown because we’re lacking in good studies on the topic.
A study by the journal Pediatrics examined two trans women who were on HRT to see if they could regain fertility. Of the post-HRT study participants, one was able to produce viable sperm after halting HRT for 5 months, while the other was unable to produce viable sperm after halting HRT for 4 months (assumedly she didn’t make it to 5 months or longer because of psychological distress of being off of HRT for that long).
So what does this study tell us? Not a whole lot! We would need a larger population size to accurately paint a picture of fertility outcomes in transgender populations. If we had sufficient studies, then we could tell you what HRT medications in particular contribute to irreversible versus reversible fertility, the duration of HRT that results in irreversible fertility, how long HRT must be halted to restore fertility, etc.
Unfortunately, we do not have such studies. This is partially due to a lack of funding for transgender research, and may also have something to do with reluctance of transgender patients to halt HRT long enough to find out.
Nevertheless, an 8 year study by Boston IVF showed that transgender men halting testosterone for an average of 4 months had similar egg yields to cisgender patients, and “all who transferred embryos eventually achieved a successful pregnancy and delivery.”
Naturally we would need more studies to follow up on this, but hey it seems pretty promising! Now if we could just convince a well-funded cryobank to do a similar study for trans women.
As it stands now, we simply don’t know enough about fertility following transgender HRT to say what the odds are of pregnancy. So it’s definitely worth considering before starting medical transition. Of course sperm or egg freezing is always an option. Adoption is also a thing that exists.
The point is though, the future for trans fertility is nowhere near as bleak as it’s often portrayed. We just need more rational conversations about it and to fund actual research that can look into it more.