>>>Mother-to-be, pregnant woman, expectant woman
>>
>>These are descriptions, not single words.
>
>As you may have heard recently, the hyphen is an endangered species, and its use is declining: heartbeat, today, nevertheless, inasmuch, et al (sure, not all necessarily originally hyphenated). I assume you have no objection to typical German portmanteau wordss (motormekaniken, for ex.), so why not "mothertobe"?

Hey, it's your language, why not? Then you'd have A word.