"Before the Birth of One of Her Children" opens with a broad meditation on death. The speaker calmly lays out the facts: all living things must die, and life's joys eventually come to an end.
Taken together with the poem's title, these lines establish the speaker's identity and mindset. While the title tells readers that the speaker is about to give birth, the four opening lines jump immediately to birth's opposite: death. All this suggests that this speaker lives in a world where death in childbirth is so common it's almost unremarkable.
But the speaker's tone betrays no surprise or discomfort with this connection. Instead, from the get-go, the poem links birth and death, suggesting that, in this speaker's mind, the two go hand in hand. Though it seems that death looms large in the speaker's mind—birth receives no mention apart from the title—the speaker is quite comfortable with this dark subject. She sees death as a simple fact of life, to be discussed calmly and with control.
A regular rhyme scheme of couplets and the steady rhythm of iambic pentameter give both the poem and its speaker an unflappable tone. (See the Rhyme Scheme and Meter sections for more on that.) And listen to the way alliteration supports the first two lines' meaning:
All things within this fading world hath end,
Adversity doth still our joyes attend;
Here, the /w/ sound connects the "fading world" to everything "within" it, while the repeated /a/ sound reflects what it describes: "Adversity," or suffering, patiently "attend[s]" even the greatest joy, waiting to strike.