Lately, pregnancy themed erotic illustrations seem to be almost on the verge of supplanting the usual alternative staples of futanari, tentacles and bondage, so a gallery of such will likely be of interest to many.
Best viewed on the Channel (particularly as the number of images there dwarfs these, and includes some very interesting images not used here).
For the sake of simplicity, let us include all the other alternative fetishistic genres (egg laying, inflation, and so on) which involve pregnancy-like features together as well.
In Japanese, there is in fact a nice all encompassing term, but alas it does not render well into English, so there seems to be little point in adopting it. Pregnancy will do.
Those images you were doubtless keen to get to:
Unseasonable I know: