According to the Parable of the wheat and tares Christ sends his Angels to gather the wheat (believers) and throw the tares in the fire. It would be difficult to gather the wheat when they had already been gathered seven years earlier.
The wheat and the tares refers to those believers and non believers who will be on the earth when Christ returns to end the age. This gathering is not in reference to the gathering of the church, but those who will have made it alive until Christ returns. According to Matt.13, the weeds are collected first. After that the angels collect the wheat. Those who will be gathered will be those unbelievers, those who will have worshiped the beast, his image and received his mark. And the wheat will be those who became believers during the time of God's wrath. The ready and watching church, will have already been removed prior to the time of God's wrath.
What you need to understand, is there are different groups that will experience different events.
The church - will be removed according to the Lord's promise prior to God's wrath, because we are not appointed to suffer God's wrath and that because Jesus already suffered it for us.
Israel - Has a decree of seventy 'sevens' sixty-nine of which have been fulfilled and therefore one 'seven' remains and will be fulfilled in conjunction with Christ's return to end the age. Unbelieving Israel will be on the earth during the time of God's wrath in fulfillment of that last seven years.
The great tribulation saints - These are those who become believers (the wheat) during the time of God's wrath and who will not love their lives so much as to shrink away from death by keeping their testimony of Jesus and by not worshiping the beast, his image and not receiving his mark. This group will be on the earth during the time of God's wrath. These are those introduced in Rev.7:9-17
The 144,000 - This will be a select group, the first fruits to God who come out of unbelieving Israel, who will most likely be preaching the good news in force. The great tribulation saints may be the result of their efforts. This group will be on the earth during the time of God's wrath.
The two witness - They will be prophesying and bringing plagues upon the earth during the first 3 1/2 years of that seven year period. They will also be on the earth during the time of God's wrath.
Unbelievers and those who worship the beast - These people names will have not been written in the book of life from the foundation of the world and will worship the beast, his image and receive his mark. They will be on the earth during the time of God's wrath.
Your comparison with the wrath of God and a woman's birth pains falls down because the birth pains are not the birth itself' The birth happens when the Baby appears not before.
The birth pains that a woman has start of mild and far apart and get more intense and closer together as it comes time for her to give birth. It will be the same why during that last seven years. Like the birth pains of a woman, the plagues of God's wrath will become closer together and more intense as the time of Christ's return to the earth to end the age nears. As I said, "sudden destruction" does not infer immediate annihilation, but is referring to the destruction of God's wrath that will be coming upon the earth. As an example, the 5th trumpet alone is five months in duration.
The problem is incomplete exegesis on yours and others part.