I suggest bevgutra ... perhaps ...
b1 carries b2=g1 from point of conception b3 to date of birth b4
if it were a tanru, wouldn't
{ .i mi bevri gutra }
be saying something like "I'm a womb, in a carrying kind of way" ?
How about
{ .i mi panzi bevri }
to mean "I'm carrying, in an offspring kind of way"
So then a possible lujvo could be something like
pazbei : panzi+bevri : pregnant;
x1 = panzi1 = bevri2 (biological offspring, thing being carried)
x2 = panzi2 = bevri1 (biological parent, thing carrying)