Gwendolyn Brooks is a highly accomplished poet, and her poem "The Mother" reflects her ability to work with language on a number of levels. The poem uses a variety of elements to give it structure, but it doesn't seem bound to any one of these elements.
End rhyme is used throughout, for example, and while the poem's rhyme often follows the format of couplets (AA, BB, etc.), it occasionally breaks out of that pattern and sometimes uses alternating rhyme (ABAB, etc.).
End rhyme is, of course, the repetition of sounds at the end of lines of a poem. Repetition is used in other ways, too, to lend structure to the poem. Key words and phrases are repeated or closely imitated, such as in the parallel grammatical forms in lines 3-4:
The damp small pulps with a little or with no hair, The singers and workers that never handled the air.
The source cited below, at enotes.com, talks about how the speaker in the poem is vacillating between various ways of making sense of the abortion or lost child:
An important unifying device in the poem is memory. Memory is constantly functioning in “the mother.” The narrator is in a fluid and changing relationship with the past, and specifically with her decisions that have drastically affected the present.
It may be possible to connect the changes in the poem's very structure to the changes in the speaker's "changing relationship with the past."
NOTE: I didn't understand the question in its original form. There's really no such thing as "structuralism in" a specific poem. Structuralism is a theoretical approach that transcends individual pieces of literature and looks for large patterns that organize and explain the individual pieces. In your question, I thus changed "structuralism in" to "structure of."