It’s not a great choice, since this isn’t the usual meaning of the word, but if the only other options are medical jargon unknown to the wider English-speaking world, it might be worth considering. (But honestly I just don’t think you should use this, or the jargon—just use a phrase to explain it.)
Anyway, there is a case for using maid or maiden in this way. To be clear, I can find no dictionary which defines it this way—and in general, barring a particular context, it would be understood as signifying that the woman is unwed and/or a virgin (as in every dictionary I could find).
Nonetheless, there is at least one circumstance in which I have heard maiden to mean specifically without children—the choice of whether the woman is a bride’s maid of honor or matron of honor.
Basically, here you have a clash between a traditional ritual, a wedding, with its associated historical assumptions, and the modern relaxation of sexual mores. These two terms reflect a historical assumption that a woman is either virginal, unwed, and without children (a maid), or else is none of those things (a matron, i.e. mother). Or, at least, an assumption that in polite company, we shouldn’t draw attention to the possibility of a woman to be some but not all of those things.
These days, in many cultures, sex before marriage is not remotely the taboo it once was. Children out of wedlock isn’t that big a deal in a lot of circles, either. Neither is necessarily shameful or something to avoid mentioning. But a bride is still supposed to have either a maid or matron of honor. Since matron means mother, labeling the bride’s sister or best friend or whatever maid of honor if she has no children and matron of honor if she does have children is a reasonable choice, and I have heard this done.
On the other hand, I have also heard maid of honor applied to married women with children (ignoring the less-known term matron of honor entirely). I have also heard matron of honor applied to women who are wed but without children (e.g. my wife in a friend’s upcoming wedding—though the term may have been chosen to differentiate her from the maid of honor, since the bride also has a maid of honor, who is unwed).
So ultimately, in this one context, maid or maiden might have the meaning you desire. But I don’t see a good way to export this meaning to other situations. The only reason it works in this context is because the artificial constraint that either maid or matron be used, and a woman without children is arguably closer to a maid than she is to a matron, maybe.