The speaker of "the mother" is… a mother.
Or is she?
This is the poem the question asks: can you be a mother, if you have aborted your children? What makes a mother a mother? Is "the mother" actually "a mother"?
The answer to this question depends on how you define motherhood. Our speaker is thoughtful, sorrowful, and full of love for her children—even though she doesn't have any, because she's aborted her pregnancies. How you feel about the mother might depend on how you feel about abortion rights—or it might not at all.
The cool thing about this poem is that it asks us to imagine ourselves in the speaker's shoes, to inhabit her position. It doesn't ask us to agree with her decision, but it does ask us to hear her voice, her feelings, and to understand the depth of her love. It paints a portrait, and asks us to draw our own conclusions about the speaker.
Tellingly, the speaker has her own trouble drawing conclusion. It's not like she feels exactly one way or the other about the abortion(s). Instead, we get to see her try to muddle through things. In the end, all she can say with certainty is that she loves her children. It seems that, through the speaker, the poem points to love as one of the few certainties in life—and death.