It's important to note that this kind of fanfiction goes against the normal gender and biological norms of the Naruto universe. That said, the world of fanfiction is all about creativity and exploring different ideas. Maybe some fans have written stories exploring this idea as a way to challenge the norms or just for pure creative exploration. But I haven't come across any myself. You might have better luck reaching out to more hardcore Naruto fanfiction communities to ask if they know of any such stories.
There could potentially be some really creative and out - of - the - box fanfictions with this concept. But finding one might be a challenge. You could try searching on specialized fanfiction websites and use specific search terms like 'Kakashi Sasuke non - traditional relationship fanfiction' and then look through the results to see if there are any that involve the idea of Sasuke being pregnant. But remember, this is a very unusual concept even for fanfiction.