Because the Lord had closed Hannah’s womb; 1 Samuel

1 Samuel 1:1-8
He had two wives; one was called Hannah and the other Peninnah. Peninnah had children, but Hannah had none.
Because the Lord had closed Hannah’s womb, her rival kept provoking her in order to irritate her.
This went on year after year. Whenever Hannah went up to the house of the Lord, her rival provoked her till she wept and would not eat.
Her husband Elkanah would say to her, “Hannah, why are you weeping? Why don’t you eat? Why are you downhearted? Don’t I mean more to you than ten sons?”
In the Bible, when God has a special purpose for someone there is often something special about birth. Hannah is not alone in the bitter experience of childlessness. Sarah and Rebecca in the Old Testament and Elizabeth in the New share her pain. Isaac, Jacob, and John the Baptist - like Samuel were born as God's answer to many years of prayer. Each had a special role to play in the great plan of God.
Why?
The story is he had two wives, so they will argue and provoking another. This is the war of two women.
God did not let Hannah had a son for God has his purpose. God has a special purpose in this event.
Because the Lord had closed Hannah’s womb: this story is started from the Lord. 
The special purpose for someone there is often something special about their birth.
How?
Have faith to the Lord, God cares everyone who respects his Holy Name. God loves us forever.