All things within this fading world hath end,
Adversity doth still our joys attend;
No ties so strong, no friends so dear and sweet,
But with death's parting blow are sure to meet.
Anne Bradstreet realizes that nothing is permanent in this world. This is a dark image especially when she is talking about the coming birth of her childern. She is already afraid of being hurt by any loss that may happen to her childern. 

Before the Birth of One of Her Children