Sarah: The First Childless Woman
The number seven here is an interesting one since it usually means some completed act by God. These seven women were devout and there was no reason to punish these ladies with barrenness. The first one was mother Sarai later called Sarah. She waited until she was in her nineties before she bore Isaac which means laughter. He was the child of promise and from her barrenness all the nations would be blessed so in a sense this one child is the beginning of that blessing to all of the nations mentioned in Isaiah 54:1 above. See a better explanation in Galatians 4:27.
Other childless women in the Bible
The second woman was Rebekah. Not only was Isaac's mother barren so was his own wife Rebekah. The odds of this happening in three consecutive generations naturally are phenomenal. She prayed and then Isaac petitioned God and when she finally conceived after twenty years of marriage she had twins. These two sons were battling in her womb for the full nine months and distressed her so much that she asked the Lord God why. His answer was that two very different nations are in her womb. One that God would love and protect and one that he would not. In Malachi 1:2-3 it says that God hated Esau but loved Jacob. From Jacob comes the House of Israel, the chosen family from whom God would call his first fruits as a body of witnesses to his ways, beginning with his only begotten Son Jesus the Christ.
The third woman was Jacob's beloved wife, Rachel. She was the younger of two sisters. Jacob's uncle deceived him as he had deceived his father Isaac. Rachel produced two very important sons but only two. Joseph who symbolized the Christ in Egypt for his family because his character brought physical salvation to them from a severe famine. The youngest child in this family was Benjamin and Rachel lost her life giving birth to this child. Rachel's surrogate child through Bilhah her maid was Dan who is also represented in this list.
The fourth woman in the Scripture who was barren was Samson's mother the wife of Manoah of the tribe of Dan. She prayed to God and he permitted her to have one son who was to be one of the strongest physically of all of the judges in that period of Israelite history. Samson was given to the priests of God as a Nazarite vow from his grateful mother and his hair was never cut until a crafty Philistine woman Delilah tricked Samson into telling her what made him so strong and supernaturally powerful. His resolve proved to bring the downfall of the Philistines and their god Dagon.
The fifth woman was the second wife of Elkanah the Ephraimite who was called Hannah. She also prayed and they thought that she was drunk but the Lord God heard her prayer and she was given a son called Samuel. She too was grateful and dedicated her only son to the priests of the Lord God of Israel. After he was weaned he lived in the High Priest's house and took over the judgeship when Eli's and his own sons died for their sins. Samuel was responsible for anointing both Kings Saul and David.
The sixth woman was the first wife of David, Saul's daughter Michal. She loved David but her father took her out of David's house and annulled their marriage and gave her to another. She was the prize for the man who could bring down the dreaded Goliath of Gath. There is some jealousy and broken promises in this story.
The seventh and final woman of the Scripture was Elizabeth the wife of Zacharias who was barren but in her old age conceived a son. This son was the cousin of Jesus of Nazareth. He was the son of the Levitical priestly clans and was called John the Baptist. Jesus called him the greatest man born of woman. He was killed by Herod the Great to please his stepdaughter's lustful wishes for a charming dance on his birthday.
So when God closes a womb and then opens it there is a very profound reason for doing so. Each of these sons played a vital role in the history of the Nation of Israel and their spiritual or symbolic counterparts in her future. The tribes represented by these six sons are Israel and Esau, Joseph, Ephraim, Dan, Levi, Benjamin. The only one whose womb remained closed (childless) was the first wife of David, Michal. And you do notice that each of these women had only sons and NO GIRL CHILDREN showing a special purpose for these miracles to take place in the plan of God.
I get the feeling that these seven initially childless women represent the spiritual completion of the necessary steps toward the telling and reception of the gospel message. From the Son of Promise to the Voice Crying in the Wilderness, each one represents some aspect of what we can expect to be fulfilled in the future.