Asyndeton adds to the poem's gentle, soothing rhythm and to the speaker's meditative tone. In lines 7-8, for example, the speaker uses asyndeton while describing the metaphorical "wood" of her daughter's sleep:
dark, peaceful, sacred,
acred in hours.
The lack of any coordinating conjunction ("and") between "sacred" and "acred in hours" speeds the poem up a little, and it also suggests that this list isn't necessarily a complete one. It's as if the speaker could go on and on describing the wonderful characteristics of her child's sleep. The lack of conjunctions also eliminates any sense of hierarchy between the different parts of the sentence; it's just as important that the child's sleep is "dark" as it is "acred in hours"—or that she has as much time to sleep as she needs.
There's more asyndeton in lines 11-12. While sleeping, the speaker's daughter is:
without time, without history,
wordlessly good.
Again, the lack of coordinating conjunction between "history" and "wordlessly good" speeds up the poem, making it feel as though the speaker is just thinking aloud while she watches her sleeping daughter. Asyndeton also makes this list feel very similar to the previous one so that even though there is no actual repetition between those lines and these, the rhythms of the poem feel familiar and therefore soothing.
The speaker turns to asyndeton one last time in the poem's closing lines:
gazed back, maternal, wise,
with its face of moon.
Again, the lack of any conjunctions here helps the poem feel more soothing and contemplative.