The title of this poem names the speaker—she's "the mother." And she's not just any ol' mother. She's the mother. The interesting thing about this, of course, is that "the mother" has had an abortion (and possibly, multiple abortions). The title of the poems is referring to her as "the mother," even though she doesn't have any children.
Weird, right? Well, we've got some thoughts about this. We think that even if the speaker isn't a mother (in the sense that she has living children), she's still had the experience of pregnancy, and she still loves and mourns the children that she's never had. She feels like a mother who has lost children, even though she decided to terminate her pregnancy.
But wait—Brooks's title is in lowercase letters, which is a little odd for a title. It's almost like Brooks is diminishing her mother status in these lines. Or maybe she's challenging the idea of her being a mother altogether. What say you? Is Brooks doing some super-sneaky undermining of her own title here?
In any case, what the title do is set up the mind in which this tortured thought process takes place (check out "Setting" for more on this). We're right there with the mother as she tries to make sense of her actions. It's a difficult convo to have with yourself, and not even the title—is it sincere? mocking?—is free from that difficulty.