Regarding the use of finasteride by men planning to father a child, the Farjo Hair Institute endorses the National Institute for Health and Care Excellence (NICE) statement:
“Although finasteride is excreted in semen, there is no need for a man to use a condom if his sexual partner is pregnant or likely to become pregnant, as the amount of finasteride excreted following a 1mg dose is too small to be harmful”.
https://cks.nice.org.uk/topics/alopecia-androgenetic-male/prescribing-information/finasteride/
Having said this, foetus abnormalities can develop without an obvious reason. From an emotional point of view, if that were to happen, you may agonize and go back and try to see if ‘you did anything wrong’. This may sound illogical or unscientific but that is human nature.
Therefore, if you think you are so inclined then we suggest for at least the 1st 3 months of pregnancy you stop taking finasteride for peace of mind. Clearly though, if you did stop the finasteride even for this short period, you risk losing any hair benefits you gained in the first place.
Many people chose to substitute finasteride with another medication like Minoxidil at least on a temporary basis. If you would like to do that, we recommend you overlap the two for 2-3 months before stopping the finasteride. This will allow the benefit of the new medication to kick in before losing the benefit of finasteride.