Order the celebration before the circumstance changes and the body starts behaving like someone who already won.
Celebration ordered ahead of the circumstance is a deliberate state change, and state runs upstream of everything else: move the body into song and the emotion follows, and a person then acts at the level of the identity that emotion belongs to.
Yahweh hands her the label before he hands her the children, and nobody outperforms their own label for long. Barrenness had been an identity issued by an entire community, carrying its own posture and its own silence, and the singing breaks that posture while the evidence is still absent. The song makes room for the offspring rather than rewarding their arrival. Wait to feel like a mother before behaving like one and the decision belongs to conditions permanently.