A baby has been born from an embryo frozen for nearly 25 years - possibly the longest gap between conception and birth since IVF began. The embryo was donated by a family in the US and has become the first child for a woman who would herself have been only one when the baby was conceived.
The "would have been" constructions are used primarily to refer to unreal situations (mainly past events which cannot be undone or done otherwise): It would have been nice if he had thanked you. But here we've got a precisely defined occurrence, nothing uncertain about it. Why does the sentence not go then as a woman who herself was only one when the baby was conceived? What's the point of using "would have been" here?