The speaker in this poem is coming to terms with the loss of her uterus and all that is had represented to her as a female and mother. It reads like a sad goodbye letter to a close, difficult friend.
The tone in this poem is, mournful. This tone has given way to a self-mocking, yet more accepting view. Even in her major crisis, the fertile mind will see the mortal body through.
In "Poem to My Uterus", I think the theme is, old age. In the majority of Clifton's poems she looks at the experiences women face through the ages. She fuses images of nature, female sexuality, etc.
In this woeful poem, the poet addresses her uterus that's about to be removed as an "old girl". This is a term that is both affectionate