This is a question not directly addressed in scripture. Many Christians believe in an “age of accountability” or “fore-ordination” or “predestination” and there are answers in all these doctrines. None of these answers are direct or simply found in scripture.
What I write here is not commonly taught and is unproven. There is some guidance I can offer however.
We have to look at the precedents in Scripture. We have to examine the heart of God and His Justice, and Mercy.
The first precedent is found in 2 Samuel 12:15–23. Therein is the story of the adulterous affair of King David and his lover, Bathsheba, the wife of an Israelite war hero. The baby was to be born a bastard child. It would be assumed in many cultures to be a cursed baby and shunned socially.
As you read the story look at the last sentence.
2 Samuel 12:15–23 states:
And the Lord struck the child that Uriah’s wife bore to David, and it became ill. 16 David therefore pleaded with God for the child, and David fasted and went in and lay all night on the ground. 17 So the elders of his house arose and went to him, to raise him up from the ground. But he would not, nor did he eat food with them. 18 Then on the seventh day it came to pass that the child died. And the servants of David were afraid to tell him that the child was dead. For they said,“Indeed, while the child was alive, we spoke to him, and he would not heed our voice. How can we tell him that the child is dead? He may do some harm!”
19 When David saw that his servants were whispering, David perceived that the child was dead. Therefore David said to his servants, “Is the child dead?”
And they said, “He is dead.”
20 So David arose from the ground, washed and anointed himself, and changed his clothes; and he went into the house of the Lord and worshiped. Then he went to his own house; and when he requested, they set food before him, and he ate. 21 Then his servants said to him, “What is this that you have done? You fasted and wept for the child while he was alive, but when the child died, you arose and ate food.”
22 And he said, “While the child was alive, I fasted and wept; for I said, ‘Who can tell whether 2the Lord will be gracious to me, that the child may live?’ 23 But now he is dead; why should I fast? Can I bring him back again? I shall go to him, but he shall not return to me.”
Clearly the ancient King of Israel, said to be a “man after God’s own heart” believed two things. 1. He believed that God would take him to heaven after he died, and, 2. he would see his dead son.
The second precedent is the record of the gestation periods of John the Baptist and Jesus. After Mary becomes pregnant,
The Gospel of Luke 1:39-41 states:
39 At that time Mary got ready and hurried to a town in the hill country of Judea, 40 where she entered Zechariah’s home and greeted Elizabeth. 41 When Elizabeth heard Mary’s greeting, the baby leaped in her womb, and Elizabeth was filled with the Holy Spirit.
Clearly, the Baby who was later born as John the Baptist, and was likely in the second to third trimester in the womb, was cognizant of the presence of Mary and the unborn Jesus, the Son of God.
Your unborn baby is a person. They have done no wrong. They are cursed by sin though, as we all are.
The third precedent comes from our Lord Himself
The Gospel of Matthew 18:14 states
Jesus said, "Let the little children come to me, and do not hinder them, for the kingdom of heaven belongs to such as these."
It is clear that while we are all born with a sinful nature, a child in the womb and a small infant have no ability to commit a sin. It is clear that as they mature, they will sin as all of us do. Small children are precious to our Lord. Is this the reason?
Therefore, if you believe in Jesus as your personal Saviour and you find yourself pregnant or nursing at the time of His Return, you have good cause to believe that both you and your child will be saved, instantly transformed and taken away. Pray for your unborn child every day. Bless your unborn child, and when he or she is born, continue to pray for them every day. Bless them in every way you can, because God loves them from the time they were conceived.
What if you are not a follower of Jesus when He returns, and you are also pregnant or nursing? Your child is loved just as much by God as a believer’s child. Your child has also not sinned. God is no respecter of persons. He treats all the same by the same rules. As an unbeliever, you will be left behind, but the non-believing mother may find her child disappears in an instant, like all the Believers disappeared. Millions of mothers around the Globe may awaken, having been pregnant when they went to bed and being barren when they awake.
On a separate note, God alone grants life. It is not clear to me if, after the Holy Spirit has departed from the earth with the Believers, if anyone will be able to conceive. These are issues I do not yet understand. What would a childless world be like? Food for thought.