"Lord, they came to you in their distress; when you disciplined them, they could barely whisper a prayer. As a pregnant woman about to give birth writhes and cries out in her pain, so were we in your presence, Lord." NIV translation
The song now speaks of the great revival that has taken place during the Great Tribulation and that reminds us of the purpose of that period of time.
After the church is removed from this world, there will be three groups of people left. They are the 144,000 witnesses, those who do not believe in the existence of God, and those with a religion. At this point, God's focus shifts to the Jewish people and bringing them back to a right relationship with Him.
We see, from this passage, that many will come to faith in Jesus Christ and, in fact, it will be the greatest "revival" that the world has ever seen. There may still be Gentiles that accept Him but the focus is on the Jews. We also note that this revival only takes place after the Jewish people have exhausted themselves in their attempts to reach God through "religion".
The prophet compares this to the extended labor of a pregnant woman. Although I do not know from personal experience, I can imagine the pain that a woman goes through in bringing a child into this world.
This comparison reminds us that it is God who gives a child life but the woman has the privilege of caring for the baby and introducing it to this world. In the same way, Israel was to "carry" the faith until the arrival of the Messiah which is Jesus.
We are also reminded that the pain that is associated with this wonderful event is the result of the sin of Eve (see Genesis 3:16). In the same way, the "pain" that the Jewish people experienced during the Great Tribulation was a result of their sin of rejecting the fact that Jesus was and is the Son of God. Just as the pain of childbirth is normally made worthwhile by the birth of the infant, the sufferings of this period of time are worthwhile because they produce repentance which, in turn, leads to the new life found in Jesus Christ.