A CHILDS SLEEP
EFFECT
with the help of several literary devices, and different types of imagery used throughout the poem, the effect the reader gets is that of tranquility, peace and innocence. although the setting is dark, like a nightmare, the reader yet gets a sense of security, and a positive energy from certain lines through the poem. the effect created makes it look like a bitter sweet memory, with the emotions of the reader changing through the poem. 
MEANING
the title of the poem is quite simple, it intends to show the basic idea of a child while it sleeps.
the overall idea of the poem is to show the innocence of a child sleeping and how a humans dreams progress as they grow up. By using "without time" the poet is able to add to this effect. the poem is meant to be very gentle, but due to the silence that is shown throughout the poem, the slightest sound feels very loud, harsh and rash. the moon is also used as a method of protection, as when the moon light goes onto the child, it gives the mother a sense of security and reassurance that her baby is safe.
LITERARY DEVICES
The different literary devices that Duffy used add on to the effect created, only to make it more enriching for the reader. the different literary devices she uses are:
IMAGERY
STRUCTURE
Metaphor: the comparison between two different things, the phrase "her sleep was a small wood" compared the silence of the baby sleeping to the peace and quiet you feel in the woods.
Repetition of words or phrases: "without time, without history" sleep is not governed. "repetition of the letter ''S" in "she was the spirit that lives" creates a mysterious sort of effect like a whisper that creates a sort of suspense as well. 
Paradox: the contradictory statements used by Duffy, such as "I could not enter there, I could not leave"
hard consonant: the use of "d" "b" and "p" in "a pebble dropped" creates a harsh sound, which from the context is at night, giving it a sort of spooky feeling. 
Alliteration: the repetition of the letter "H" in the phrase "hearing her breathe" 
caesura: "went to the window. the grater dark...." this creates a pause in the flow of the poem, and switches the focus of the reader to engage the reader more in what is being done. 
personification: "with its face of moon" it gives the effect of a maternal and experienced moon 
Duffy used a lot of imagery throughout the poem, in ways such as visual, auditory, and olfactory. the ways in which she did so made the poem more engaging for the reader. the ways in which she used these forms of imagery were:
Visual
Auditory:
Olfactory
"i spoke her name, and a pebble dropped": the sound that comes from this phrase
"hearing her breathe": the sound of the sleeping baby creates a sort of tranquil melody that keeps playing again and again
"A child's sleep": the title of the poem itself is a form of visual imagery, where the reader can picture a child sleeping
"dark, peaceful and scared": creates a positive, and negative sort of feeling for the reader about what they are picturing
"in the heart of such woods": gives the look of a certain life force, that is roaming around the woods and the reader pictures a sort of peaceful location with such woods. 
"perfumed with flowers" the smell of flowers is usually a peaceful and positive scenario, so the reader is transported to that kind of location
there are 5 stanzas and 4 quatrains. the definite structure that is there throughout the poem shows the stability of the poem, and in turn the stability of the baby's sleep. the rhyming structure is ABCB