Emunah U’Bitachon 1:5

We are presented with another system – one designed with incalculable and other-worldly understanding – that testifies to the wisdom of its maker and its existence is praise to him: The mechanism of male and female union, designed to ensure the eternity of the world. This includes the wondrousness of each gender's organs and the creation of the desire that necessitates their use. Because we are habituated to them, we don't recognize the awesomeness of the Creator – all these He made and established to last forever!

Another mystery – fascinating and wondrous – is the forming of man in his mother's body. He lives there for nine months, a pleasant and well-ordered life. He develops and grows, and when his time comes to leave, he breaks through, and leaves! This is all already hidden in the universe's capabilities, involving complementary forces. All these many forces need to be coordinated, with each doing precisely its job perfectly, until the fresh and ready baby is produced. And the goal of all this effort was already planned in the mind of the Creator of all from its very beginning.

And when the baby does enter the world, his mother's breasts – which nurse him with nutritious milk – are created for him. And the Creator declared that there should be a powerful maternal instinct in the mother, to tirelessly care for her baby. We call this the mother's love for her young. (The child also possesses a prepared behavior in that it knows how to suckle from its mother and to take pleasure from her milk.)