I have noticed that excellent answers to the two connected questions (1) why god allowed birth defects and(2) whether mentally retarded persons can go to heaven are given in got
question.org which is reproduced below.Though the basic answer to both the questions is that ‘we do know exactly’ as nothing specifically on the subject is said in the bible , there is hope as explained therein .
Question: “Why does God allow birth defects?”
Answer: The ultimate answer to this difficult question is that when Adam and Eve sinned (Genesis chapter 3), they brought evil, sickness, disease, and death into the world. Sin has been wreaking havoc on the human race ever since. Birth defects occur because of sin…not because of sins the parents or the baby have committed, but because of sin itself. The hard part of the question is why God allows people to be born with terrible birth defects and/or deformities. Why doesn’t God prevent birth defects from occurring?
The book of Job deals with the issue of not understanding why God allows certain things to occur. God had allowed Satan to do everything he wanted to Job except kill him. What was Job’s reaction? “Though he slay me, yet will I hope in him” (Job 13:15). “The LORD gave and the LORD has taken away; may the name of the LORD be praised” (Job 1:21). Job didn’t understand why God had allowed the things He did, but he knew that God was good and therefore continued to trust in Him. Ultimately, that should be our reaction as well. God is good, just, loving, and merciful. Often things happen to us that we simply cannot understand. However, instead of doubting God’s goodness, our reaction should be to trust Him. “Trust in the LORD with all your heart and lean not on your own understanding; in all your ways acknowledge Him, and He will make your paths straight” (Proverbs 3:5-6).
Ultimately, the answer to this question has to be “I don’t know.” We will never be able to fully understand God and His ways. It is wrong for us to question why God allows something to occur. We simply have to trust that He is loving, good, and merciful – just like Job did – even when the evidence seems to indicate the opposite. Sickness and disease are the result of sin. God provided the “cure” for sin in sending Jesus Christ to die for us (Romans 5:8). Once we are in heaven, we will be free from sickness, disease, and death. Until that day, we will have to deal with sin, its effects, and its consequences. We can praise God, though, that He can and will use birth defects and other tragedies for our good and His glory. John 9:2-3 declares, “His disciples asked Him, ‘Rabbi, who sinned, this man or his parents, that he was born blind?’ ‘Neither this man nor his parents sinned,’ said Jesus, ‘but this happened so that the work of God might be displayed in his life.’”
Question: “Do mentally ill people go to heaven? Does God show mercy to those who are mentally challenged, disabled, or handicapped?”
Answer: The Bible does not specifically say whether or not mentally ill people go to heaven. However, there is some biblical evidence that anyone who is not able to make a decision for salvation is covered by Christ’s death. This is similar to how it is commonly believed that children are automatically taken to heaven when they die until they reach the point in which they are able to make a decision for or against Christ. David had a child die, and he comforted himself with the thought, “Can I bring him back again? I will go to him, but he will not return to me” (2 Samuel 12:23). David knew that he would see his child in heaven one day. From that statement, we can assume that babies and young children were, by God’s grace, covered for salvation by Christ’s death.
We can postulate that mentally handicapped people are covered by this principle as well. The Word of God does not specifically say this, however. Knowing the love, grace, and mercy of God, this would seem consistent with His character. Any person who is mentally challenged to the extent that he could not be aware of his sinful state and believe in Christ for salvation is in the same category as a child, and it is not unreasonable to assume that person is saved by the grace and mercy of the same God who saves babies and small children.
As in everything, however, we must be careful not to be dogmatic about any issue the Bible does not specifically address. We do know that Jesus receives as His own all whom the Father has given to Him and He will lose none of them along the way (John 6:39). Jesus said of these, “And I give to them eternal life, and they shall never ever perish, and not anyone shall pluck them out of My hand” (John 10:28). We can take comfort in knowing that our God’s plan is always perfect, He always does what is right and just, and His love and mercy are infinite and everlasting.