pea in the pod

Dear all,
Would you please help me out with the following idiom "A pea in the pod", and actually another one "A bun in the oven" - it should be something referring to pregnancy or maternity.
The thing is that all the idioms in Russian with regard to maternity seem to have a negative conotation. Would you please therefore assist me in making the phrase sound positive.
Thank you in advance,

--Vivi answers
see [bun in the oven]