A birth is none other than a transition from the invisible to the visible

"A birth is none other than a transition from the invisible to the
visible, from the immaterial to the material, from thought to
manifestation. In our body, it is the moon, the archetype of the
feminine, that presides over all forms of incarnation. In winter,
the period during which the nights are longest and the life of
nature slows down, conditions are less favourable for outward
manifestation but more favourable, on the other hand, for inner
life: human beings feel the urge to go within themselves to
prepare the birth of the child of light, which is represented in
some traditions by the symbol of the pearl. The pearl, coming as
it does from the sea, is, like the sea, related to the moon.
On the sephirotic tree, the pearl oyster is Yesod, the sephirah
where the moon is found. In the cosmic body, Yesod represents the
genital organs. That is where the pearl must be formed. This
pearl represents the purest quintessence of love. The pearl
oyster is the feminine principle, which brings a pearl, the
divine child, into the world."

Omraam Mikhaël Aïvanhov