In most if not all Spanish dictionaries I've checked, embarazada is only ever listed in its feminine form unlike all other adjectives I can think of.
Is this semantic because it's considered that males can't be pregnant, or is it a real lexical property of the word? Are there other words with this property? I don't think I've checked as many dictionaries for preñada and encinta.
(I know these three words are listed in Wiktionary in their masculine form, but I was at least partly responsible for that and it was based on hunting down a few masculine forms rather than following any canonical reference.)