The Rice University Neologisms Database

Pregnant, in gestation. In this instance ‘o’ most likely is a meaningless morpheme added to make the expression a more rounded diminutive of a previous clipping of pregnant to “preg”. However, the ‘o’ may also come as a borrowed morpheme from Spanish languages where the addition of ‘o’ can generally make a word an adjective, although this generally applies to male-applicable adjectives.