Why does childbirth still hurt?

Presumably, before God cursed Eve with pain of childbirth, He had created her body in such a way to give birth without pain. And yet now childbirth is painful, therefore He changed the design of her body so that the physicality of her baby being delivered from her body is painful. Doesn't it have to do with the physical design of a woman's body- specifically God's design (re-worked? design) of her womb and birth canal that now she experiences pain? And therefore the design of woman is forever changed as long as we inhabit these earthly bodies? Our bodies did not physically revert back to the pre-fall time when Jesus was resurrected, but He did proclaim that by His wounds, we are healed- and further more He heals us from ALL diseases. Not that childbirth is a disease! Certainly it is not. But it can be concluded that we can believe in Christ's power and His miracle for ease in childbirth- otherwise we wouldn't feel empowered to pray for a woman to have an easy birth, free of complications and even free of excruciating pain. We are in fact empowered to pray for many physical maladies because we believe in the living power of Jesus to heal our physical bodies, while we are still on earth- just as He performed many miracles of physical healing when He walked the earth. And now He walks the earth IN us, His Holy Spirit in us!

You are mistaken in stating that the pain of childbirth is in retribution for eating the fruit, That punishment was given by God as a punishment for the sin of disobeying his command not to eat of the tree of the knowledge of good and evil.

The reason that the punishment continues today is not because of Eve's original sin, but instead would appear to be the reason God did not want mankind to have the knowledge of good and evil in the first place, which appears to be because once Man and woman gained the knowledge of good and evil:

Genesis KJV 8:21 And the LORD smelled a sweet savour; and the LORD said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart is evil from his youth; neither will I again smite any more every thing living, as I have done.

After obtaining that knowledge man and woman are unable to resist the apparent attractiveness of sin.

God in his omniscience was aware of this flaw in mankind's character, which is evident from our early youth, where a child will willfully disobey its parents, and it is true that man will willfully disobey God when confronted with the attractiveness of sin. One of the most prevalent indications of this is man's propensity to engage in illicit sex. Although all of civilized mankind is aware that adultery is wrong not only in God's eyes, but also in man's concept; will cave to the allure, and this is true of many Christians as well.

The pain of Childbirth remains because once Eve gained the Knowledge of good and evil Satan has had a tool at his disposal which he uses to create a separation between God and man, just as he did with Adam and Eve in the Garden. Satan still uses that same ploy on mankind today;

Genesis 3:4 And the serpent said unto the woman, Ye shall not surely die:

Satan has overshadowed God's words about dying with the lie that Disobeying God will send one to Hell. And that concept is cloaked in another deception, just as it was for Eve.

Genesis 3:6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.

There are two great lies in that Scripture:

1. that it was pleasant to the eyes, The only reason sin is attractive to the eye is because mankind has been blinded to the truth. If man could see all of the hurt his disobedience causes, not only the pain and disillusionment of people, but the hurt it gives God, which is so great that he heaped his vengeance on his innocent son. and so just as with man it is the innocent who are hurt the most as it is with God. Jesus did not die for the sins of a few, but that all of the sins of mankind for all time could be forgiven.

2. a tree to be desired to make one wise, Wise here is a misnomer in that choosing eternal punishment over eternal life is not only unwise it is foolhardy.

And last of all it need be remembered that God does not punish women today for the sin committed by Eve, that punishment is in retribution for the individual's sin of disobedience which is gained at our first disobedience of God, which for most of us is the first time we said "no" to our parents.

Hope this helps.

God doesn't exactly say that the pain of childbirth is a punishment. We automatically categorize it as a punishment because it is physically unpleasant. Another interpretation of the punishments" of Genesis is that they were actually for our own good. Adam and Eve became victims and slaves to their own pride, by their own choice. Humility, on the other hand, is the true path to the Kingdom of Heaven (Matthew 5:3). The afflictions that God "imposed" on Adam and Eve served to curb their pride and self-will and keep them from still further spiritual harm. God chastens those whom He loves (Proverbs 3:12; Hebrews 12:6).

Your question amounts to: "Why do the punishments of original sin remain after baptism?"

The punishments are, as Gen. 3:16-19, says:

For women:

1. painful childbirth
2. subjection to man

For men:

1. hard work, toil, etc. for bread-wining

St. Thomas Aquinas addresses the question of "Whether Baptism should take away the penalties of sin that belong to this life?," saying (my emphasis):

Baptism has the power to take away the penalties of the present life yet it does not take them away during the present life, but by its power they will be taken away from the just in the resurrection when "this mortal hath put on immortality" (1 Cor. 15:54). And this is reasonable. First, because, by Baptism, man is incorporated in Christ, and is made His member, as stated above (Article [3]; Question [68], Article [5]). Consequently it is fitting that what takes place in the Head should take place also in the member incorporated. Now, from the very beginning of His conception Christ was "full of grace and truth," yet He had a passible body, which through His Passion and death was raised up to a life of glory. Wherefore a Christian receives grace in Baptism, as to his soul; but he retains a passible body, so that he may suffer for Christ therein: yet at length he will be raised up to a life of impassibility. Hence the Apostle says (Rm. 8:11): "He that raised up Jesus Christ from the dead, shall quicken also our [Vulg.: 'your'] mortal bodies, because of His Spirit that dwelleth in us [Vulg.: 'you']": and further on in the same chapter (Rm. 8:17): "Heirs indeed of God, and joint heirs with Christ: yet so, if we suffer with Him, that we may be also glorified with Him."

Secondly, this is suitable for our spiritual training: namely, in order that, by fighting against concupiscence and other defects to which he is subject, man may receive the crown of victory. Wherefore on Rm. 6:6, "that the body of sin may be destroyed," a gloss says: "If a man after Baptism live in the flesh, he has concupiscence to fight against, and to conquer by God's help." In sign of which it is written (Judges 3:1,2): "These are the nations which the Lord left, that by them He might instruct Israel … that afterwards their children might learn to fight with their enemies, and to be trained up to war."

Thirdly, this was suitable, lest men might seek to be baptized for the sake of impassibility in the present life, and not for the sake of the glory of life eternal. Wherefore the Apostle says (1 Cor. 15:19): "If in this life only we have hope in Christ, we are of all men most miserable."

A common Evangelical answer to your question would be that even though Christ's work on the cross was* to redeem mankind from the effects of the fall, there is a now-and-not-yet-ness in regard to the complete outworking of the victory won at Calvary (*ie 'was' is really 'was'/'is'/'will be') . In particular, the physical creation in general and our mortal bodies in particular will be amongst the last to experience full redemption from the effects of the fall, and will do so only upon Christ's return in glory:

Present Suffering and Future Glory

18 I consider that our present sufferings are not worth comparing with the glory that will be revealed in us. 19 For the creation waits in eager expectation for the children of God to be revealed. 20 For the creation was subjected to frustration, not by its own choice, but by the will of the one who subjected it, in hope 21 that the creation itself will be liberated from its bondage to decay and brought into the freedom and glory of the children of God.

22 We know that the whole creation has been groaning as in the pains of childbirth right up to the present time. 23 Not only so, but we ourselves, who have the firstfruits of the Spirit, groan inwardly as we wait eagerly for our adoption to sonship, the redemption of our bodies. 24 For in this hope we were saved. But hope that is seen is no hope at all. Who hopes for what they already have? 25 But if we hope for what we do not yet have, we wait for it patiently. - Romans 8:18-25 NIV

Paul seems to be saying here that because mankind fell and suffered the consequences of sin as a curse, the rest of creation (which had been committed to the stewardship of mankind) was subjected to 'frustration' in order that it's 'groans' could testify to the need for the redemption and glorification of it's fallen race of stewards - this is a theological rationale for the current imperfections in nature.

Compare also 1 Corinthians 15:51-55 which speaks of the Resurrection to come as an overcoming not just of death, but also of the 'perishable' or 'corruptible' nature of our bodies - new resurrected bodies will be imperishable and incorruptible; and further, in the New Jerusalem:

‘He will wipe every tear from their eyes. There will be no more death’ or mourning or crying or pain, for the old order of things has passed away. - Revelation 21:4 NIV

So a complete deliverance from pain awaits the passing away of the old order.

An alternative (currently minority) perspective, is that the benefits of Christ's work can largely be appropriated by faith in this present age as:

Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: “Cursed is everyone who is hung on a pole.” - Galatians 3:13 NIV

“He himself bore our sins” in his body on the cross, so that we might die to sins and live for righteousness; “by his wounds you have been healed.” - 1 Peter 2:24 NIV

Note that 'redeemed' and 'healed' are past tense, establishing a basis for belief that Christ's words on the cross of 'It is finished' can legitimately be given a broad application that would cover deliverance from all aspects of the curse, including the pains of childbirth. Under this framework, the Saints of God no longer 'die', but merely go 'to sleep' to awaken at the last trumpet.

Further, although it is part of a difficult passage to interpret, women are given hope that:

But she will be delivered through childbearing, if she continues in faith and love and holiness with self-control. 1 Timothy 2:15 NET

Could well include deliverance not just from death, but also the pain of the curse. If some regard that as a fanciful application of this particular scripture, perhaps they will be more reticent to deny that:

Everything is possible for one who believes. - Mark 9:23b NIV

Can be a legitimate basis for such a belief. In any event, there are many that have dared to believe such a thing and have subsequently testified to encountering God's deliverance in this manner.

PS Your talk of the Old Testament and shrimps is a bit of a red herring with regard to the substance of this question, but the point should be made that Jesus explicitly did not 'revoke' a 'bunch of other stuff in the Old Testament' - He came to fulfill the law perfectly. That laws expressly given to mark Israel, and subsequently the Jews, apart as the Covenant people the Messiah would come through were not mandated holus-bolus on Gentile converts does not constitute a 'revocation' and each law in the Old Testament should be understood in it's proper context and evaluated for utility as a guiding principle (not moral obligation that brings condemnation and judgment by it's transgression) in the life of a New Covenant believer. If Gentile converts had by and large followed the Jewish dietary laws (as a guiding principle for healthy living), particularly with regard to eating pork and shellfish, no doubt countless thousands of them would have experienced consequent benefit in extended and overall more healthy lives.