Genesis 38:1

¹ And it came to pass at that time, that Judah went down from his brethren, and turned in to a certain Adullamite, whose name was Hirah.

Genesis 46:12

¹² And the sons of Judah; Er, and Onan, and Shelah, and Pharez, and Zerah: but Er and Onan died in the land of Canaan. And the sons of Pharez were Hezron, and Hamul.

In Genesis 38:27, Psalm 48:6, Isaiah 23:4, and Revelation 12:2, this signifies to conceive and bring forth the things which pertain to spiritual life. Travail here signifies also the doctrine of the New Church and its difficult birth. (Apocalypse Revealed 535)

Travail signifies acknowledgment of the good and truth of the church in faith and act. (Arcana Coelestia 4919)

'To travail in birth' signifies conceiving and bringing forth the elements of spiritual life.