When a woman reaches her 16th week of pregnancy, the baby in her womb begins to develop the ability to hear. It starts to recognise and make itself familiar with it's mothers speech as well as other sounds. In fact, it is also scientifically stated that, if there is a certain tune that the mother sang in pregnancy, the child would remember that tune even after it's born!
Now imagine, if a pregnant woman was to recite Qur'an regularly and loudly while she was carrying her baby in the womb. Imagine the effect it will be having on the baby? When that child is born, he or she will remember the recitation of the Quran and be familiar with it from a very young age. Not only that, but a child may preserve the tune/recitation in their memory.If something like this does not amaze you and remind you of the Greatness of Allah, then what will?
When they say, 'start your children early', it does not mean when they reach 4, 5,6. Rather, Islam stresses that it all starts when the baby is in the womb. So, the lesson to take away is... start your kids early!