Specifically things like chicken or most fish.
technical carrying eggs or young; pregnant. "the retroverted gravid uterus"
in lay (entry 'lay' section phrases
(of a hen) laying eggs regularly.
Definition of gravid in English: adjective 1 technical Carrying eggs or young; pregnant: the retroverted gravid uterus
Although it doesn't especially refer to fish, birds, or the like, the French loanword enceinte is quite useful.
enceinte. (n.d.) Random House Kernerman Webster’s College Dictionary. (2010). Retrieved August 18 2015 from http://www.thefreedictionary.com/enceinte
Its probable etymology from Latin incincta "ungirded" alludes to the gravid female's preparation for imminent parturition.
I endorse "gravid" since I've heard it used to indicate oviparous females with eggs. The implication is fertile eggs but they needn't be. Possessing eggs which have not yet been laid. Proper for any egg layer, be it a queen ant, octopus, blue-footed booby, alligator, shark (those that don't do live birth...) or platypus & echidna.
According to Merriam-Webster's site, from:
"Latin gravidus, from gravis heavy. First Known Use: 1597"
But note that this is after 100+ years after "pregnant":
"Middle English, from Latin praegnant-, praegnans carrying a fetus, alteration of praegnas, from prae- pre- + -gnas (akin to gignere to give birth to) — more at kin. First Known Use: 14th century".
There are plenty of synonyms - heavy, quick, big, with child. I remember reading that one of the common ones, "Expecting"? was a Victorian circumlocution, because pregnancy was too "bodily" for polite society. Overall, I think we're better off leaving that sort of thinking behind us. Aesthetically, I like "With child".